Vol. 63, No. 11961 Chem. Pharm. Bull. 63, 961–966 (2015)
Note
Synthesis and Determination of Absolute Configuration of Lentztrehalose A Ming Zhang, Shun-ichi Wada, Fuyuki Amemiya, Takumi Watanabe,* and Masakatsu Shibasaki* Institute of Microbial Chemistry (BIKAKEN), Tokyo; 3–14–23 Kamiosaki, Shinagawa-ku, Tokyo 141–0021, Japan. Received July 31, 2015; accepted August 22, 2015 The synthesis of lentztrehalose A, a naturally occurring trehalose derivative exhibiting various biological activities including autophagy-inducing activity, was achieved. The synthesis commenced with the selective protection of hydroxyl groups of commercially available trehalose, followed by the introduction of the side chain moiety by two methods: 1) prenylation and successive diastereoselective dihydroxylation; or 2) etherification by opening of the chiral epoxide. The present synthetic study clarified the unreported absolute configuration of the secondary alcohol part in the side chain portion. Key words
trehalose; natural product synthesis; autophagy-inducing activity; stereochemistry determination
Trehalose is a disaccharide comprising two glucoses with an α,α-1,1-linkage, that is widely used as an additive in food, medicines, and cosmetics.1) Although a variety of biological activities, including anti-tumor,2) anti-obesity,3) and bonestrengthening activities4) have been reported, use of trehalose for medicine is limited because of its degradation by trehalase under physiological conditions. Recently, trehalose derivatives lentztrehalose A, B, and C were reported as natural products of a rare actinomycete, Lentzea sp. ML457-mF8.5) The structure of each molecule can be characterized by the substituents on the 4-hydroxy group from one of the glucose molecules, which accounts for the robustness of lentztrehaloses toward cleavage of the glycosyl bond by trehalase. It is also noteworthy that lentztrehaloses exhibit autophagy-inducing activity.6) Autophagy involves lysosomal degradation of unnecessary cellular components; disorders of this physiological process result in the accumulation of abnormal proteins, which causes various diseases, such as Alzheimer’s disease, amyotrophic lateral sclerosis, Parkinson disease, and Huntington disease, making lentztrehaloses promising leads for clinical drugs.7) In this note, the synthetic method of lentztrehalose A is disclosed starting from easily available trehalose, which could be utilized for structure–activity relationship studies. Importantly, the absolute configuration of lentztrehalose A was
Fig. 1.
unequivocally determined as shown in Fig. 1 in the course of this synthetic study. The synthetic scheme is straightforward: the hydroxyl groups except for the one(s) substituted at the 4-position were protected, followed by attachment of the side chain moiety and global deprotection. The side chain part was installed by either dihydroxylation after prenylation, or opening of the optically active epoxide. The absolute configuration was determined based on the stereochemistry of the epoxide used to append the side chain portion.
Results and Discussion
The synthetic procedure is shown in Chart 1. Commercially available anhydrous trehalose 4 was subjected to acetalization conditions to afford a mixture of mono- and bisbenzylidene trehalose in which one or two of the 4,6-diols were protected. The benzyl groups were then introduced to block all of the remaining hydroxyl groups, followed by regioselective reductive opening of benzylidene acetal(s) to give 5 with two free 4-hydroxy groups, and 6 with one. The product ratio of 5 to 6 was dependent on the stoichiometry of the added reagents at the first step: 2.25 eq of benzaldehyde dimethyl acetal afforded 52% of 5 and 5% of 6, whereas 1.5 eq resulted in 14% of 5 and 39% of 6. Subsequently, prenyl bromide was treated with diol 5 to afford 7 in 44% yield and a small amount of diprenyl side product together with recovery of the unreacted substrate. In
Structure of Lentztrehaloses
To whom correspondence should be addressed. e-mail:
[email protected];
[email protected] * © 2015 The Pharmaceutical Society of Japan
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Reagents and conditions: (a) (i) PhCH(OMe)2, p-TsOH, DMF, 100°C, 4.7 h; (ii) BnBr, NaH, TBAI, THF, rt, 12 h; (iii) Et3SiH, TFA, CH 2Cl 2, 0°C, 3 h, 52% over 3 steps; (b) prenyl bromide, NaH, TBAI, DMF, rt, 12 h, 44%; (c) AD-mix-α, (DHQ)2PHAL, MeSO2NH 2, t-BuOH, H 2O, 0°C, 66 h, quant.; (d) H 2, 10% Pd/C, MeOH, rt, 24 h, quant.
Chart 1.
Synthesis of Lentztrehalose A
the next step, the vicinal diol was furnished under Sharpless’ asymmetric aminohydroxylation conditions using AD-mix-α, (DHQ)2PHAL, and methanesulfonamide in diastereoselective manner in a 9 : 1 ratio with the desired isomer as the predominant product. Finally, a conventional hydrogenolysis to unmask all of the protected hydroxyl groups completed the synthesis of lentztrehalose A in 23% overall yield. Alternatively, the side chain part of lentztrehalose A could be introduced via etherification of 6 by opening the optically active epoxide 9, which was prepared in 78% ee from the reported (S)-2-(oxiran-2-yl)propan-2-ol.8) The substrate 6 was treated with NaH in the presence of 15-crown-5 to give 10, which was followed by global deprotection under hydrogenolysis conditions, resulting in lentztrehalose A. All the physicochemical properties, including the sign of the optical rotation of the synthetic samples, were fully identical to the reported properties. A stereospecific epoxide-opening reaction between 9 and 6 allowed us to determine the configuration of the secondary alcohol part within the side chain as S. This configuration is also supported by comparing the 1H-NMR chemical shift from both of the Mosher esters. The free secondary hydroxyl group of 12 prepared from 6 in two steps was acylated with (R)- and (S)-α-methoxy-α-(trifluoromethyl)phenylacetyl (MTPA)-Cl to afford the corresponding esters 13 and 14. The difference in the chemical shift values from the surrounding protons of the esters depicted in Chart 2 matched the empirical tendency, further supporting the absolute stereochemistry of the alcohol as S.9) In summary, we established a practical synthetic protocol to obtain lentztrehalose A in 23% overall yield in 6 steps. The unreported absolute configuration of the secondary alcohol in the side chain part was unequivocally determined to be S. Structure–activity relationship studies of lentztrehaloses by applying this synthetic protocol to pursue their autophagyinducing activity are underway.
Experimental
General Remarks All reactions were conducted in flamedried glassware under an argon atmosphere unless otherwise noted. Reagents and solvents were obtained from commercial sources and used as received unless otherwise stated. Column chromatography was performed with silica gel Merck 60 (230–400 mesh ASTM) or silicagel 60 N (spherical, neutral, 40–50 µm) from Kanto Chemical Co., Ltd. Preparative TLC plates (#1.05744.0001, PLC Silica gel 60 F254) were purchased from Merck. Infrared (IR) spectra were recorded on a JASCO FT/IR 4100 Fourier transform infrared spectrophotometer. NMR was recorded on JEOL ECS-400 or ECA-600. Chemical shifts for proton are reported in parts per million downfield from tetramethylsilane and are referenced to residual protium in the NMR solvent (CDCl3: δ 7.24 ppm; CD3OD: δ 3.34 ppm). For 13C-NMR, chemical shifts were reported in the scale relative to NMR solvent (CDCl3: δ 77.0 ppm; CD3OD: δ 49.0 ppm) as an internal reference. For 19F-NMR, chemical shifts were reported in the scale relative to trifluoroacetic acid (TFA) (δ 76.50 ppm) as an external reference. NMR data are reported as follows: chemical shifts, multiplicity (s: singlet, d: doublet, dd: doublet of doublets, t: triplet, q: quartet, m: multiplet, br: broad signal), coupling constant (Hz), and integration. Optical rotation was measured using a 1 mL cell with a 1.0 dm path length on a JASCO polarimeter P-1030. High-resolution (HR) mass spectra (electrospray ionization (ESI) Orbitrap) were measured on Thermo Fisher Scientific LTQ Orbitrap XL. (2R, 3R, 5R,6R) - 4, 5 -Bis(benz yloxy) -2- ((benz yloxy) methyl) - 6 - (((2R, 3R,4S, 5R,6R) -3,4 -bis( benz yloxy) - 6 ((benzyloxy)methyl)-5-hydroxytetrahydro-2H-pyran-2-yl)oxy)tetrahydro-2H-pyran-3-ol (5) and (2R,3R,5R,6R)-4,5Bis(benzyloxy)-2-((benzyloxy)methyl)- 6 -(((2R, 3R,4S, 5R,6R)-3,4,5-tris(benzyloxy)-6-((benzyloxy)methyl)tetrahydro-2H-pyran-2-yl)oxy)tetrahydro-2H-pyran-3-ol (6) To a stirred suspension of the anhydrous trehalose (2.33 g,
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Reagents and conditions: (a) NaH, 15-crown-5, DMF, 70°C, 18 h, 30%; (b) H 2, 10% Pd/C, MeOH, rt, 24 h, 89%; (c) prenyl bromide, NaH, TBAI, DMF, rt, 12 h, quant.; (d) AD-mix-α, (DHQ)2PHAL, MeSO2NH 2, t-BuOH, H 2O, 0°C, 66 h, 45%.; (e) (R)-MTPA-Cl, TEA, DMAP, rt, 24 h, 86%; (f) (S)-MTPA-Cl, TEA, DMAP, rt, 24 h, 92%.
Chart 2.
Determination of Absolute Stereochemistry of Lentztrehalose A
6.80 mmol) in dry N,N-dimethylformamide (DMF) (30 mL) were added p-toluenesulfonic acid (p-TsOH, 59.0 mg, 0.340 mmol) and benzaldehyde dimethyl acetal (1.02 mL, 6.80 mmol) The mixture was heated at 100°C for 20 min, and under reduced pressure (ca. 160 mmHg) for 20 min under the same temperature. After backfilled with argon, additional benzaldehyde dimethyl acetal (1.02 mL, 6.80 mmol) was added, the resulting mixture was heated at 100°C for 1 h under reduced pressure (ca. 160 mmHg). Additional benzaldehyde dimethyl acetal (0.25 mL, 1.70 mmol) was added, the resulting mixture was heated at 100°C for 4 h under reduced pressure (ca. 160 mmHg). The reaction mixture was cooled to room temperature and neutralized with triethylamine (TEA) to obtain a crude solution which was directly used for the next step without any purification. To the above mentioned mixture in DMF at 0°C were added NaH (2.72 g, 60% dispersion in mineral oil, 68.0 mmol) and tetra-n-butylammonium iodide (TBAI, 176 mg, 0.476 mmol), followed by slow addition of BnBr (4.85 mL, 40.8 mmol), and the resulting mixture was warmed to room temperature gradually and stirred for 12 h. Then, the reaction solution was poured onto ice water and extracted with CH2Cl2 (3×30 mL). The combined organic layers were washed with hydrochloric acid (1 M, 20 mL), and saturated aqueous NaHCO3, dried over anhydrous Na2SO4, and concentrated. The resulting residue was purified by silica gel column chromatography (nhexane : EtOAc=6 : 1) to afford 4.89 g of benzylated product as a colorless syrup. To the benzylated product in CH2Cl2 at 0°C were added Et3SiH (11.7 mL, 73.3 mmol) and TFA (5.61 mL, 75.5 mmol). After stirring for 3 h at the same temperature, saturated aqueous NaHCO3 (100 mL) was added and stirring
was continued for 5 min. The organic layer was separated, and the aqueous layer was extracted with CH2Cl2 (100 mL). The combined organic layer was washed with saturated brine, dried over anhydrous Na2SO4, and concentrated, the resulting crude syrup was purified by silica gel column chromatography (n-hexane–EtOAc=4 : 1 to 3 : 1) to afford 5 (3.11 g, 3.52 mmol, 52% in 3 steps) as a white powder, along with 6 (337 mg, 5%, 3 steps) as a colorless syrup. Compound 6 was synthesized in a similar manner for 5 with decreased amount of benzaldehyde dimethyl acetal (1.76 mL, 11.7 mmol), anhydrous trehalose (3.57 g, 10.4 mmol), and p-TsOH (89.0 mg, 0.517 mmol) in the first step. For the second step, NaH (6.24 g, 60% dispersion in mineral oil, 0.156 mol), TBAI (268 mg, 0.726 mmol) and BnBr (11.1 mL, 93.3 mmol) were used. For the third step, TFA (5.97 mL, 80.4 mmol) and Et3SiH (12.4 mL, 77.6 mmol) were employed to afford 6 (4.00 g, 4.11 mmol, 39% in 3 steps) along with 5 (1.26 g, 1.43 mmol, 14%, 3 steps). 5: mp 101–103°C (dec). [α]D20 +79 (c=1.3, CHCl3); IR (CHCl3) ν: 3585, 3066, 2924, 2869, 2359, 1454, 1363, 1096, 699 cm−1; 1H-NMR (400 MHz, CDCl3) δ: 7.38–7.33 (m, 8H), 7.30–7.23 (m, 22H), 5.23 (d, J=3.6 Hz, 2H), 5.00 (d, J=11.4 Hz, 2H, PhCH2O), 4.79 (d, J=11.4 Hz, 2H, PhCH2O), 4.69 (d, J=12.1 Hz, 2H, PhCH2O), 4.63 (d, J=12.1 Hz, 2H, PhCH2O), 4.50 (d, J=12.1 Hz, 2H, PhCH2O), 4.44 (d, J=12.1 Hz, 2H, PhCH2O), 4.13–4.10 (m, 2H, PhCH2O), 3.87 (t, J=9.6 Hz, 2H), 3.59 (t, J=9.6 Hz, 2H), 3.56 (dd, J=9.6, 3.6 Hz, 2H), 3.53–3.45 (m, 4H), 2.38 (br s, 2H); 13C-NMR (100 MHz, CDCl3) δ: 138.9, 138.1, 138.0, 128.7, 128.5, 128.5, 128.1, 127.9, 127.8, 127.8, 127.6, 94.3, 81.1, 79.0, 75.4, 73.7, 72.5, 70.8, 70.7, 69.3; HR-MS (ESI) Anal. Calcd for C54H58O11K m/z 921.3611
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[M+K]+. Found 921.3598. 6: [α]D20 +88 (c=1.0, CHCl3); IR (CHCl3) ν: 3586, 3010, 2925, 2869, 2364, 1454, 1362, 1097, 699 cm−1; 1H-NMR (400 MHz, CDCl3) δ: 7.37–7.20 (m, 33H), 7.13–7.11 (m, 2H), 5.24 (d, J=3.4 Hz, 1H), 5.23 (d, J=3.4 Hz, 1H), 5.00 (d, J=11.4 Hz, 1H, PhCH2O), 4.99 (d, J=11.0 Hz, 1H, PhCH2O), 4.86 (d, J=11.0 Hz, 1H, PhCH2O), 4.81 (d, J=10.5 Hz, 1H, PhCH2O), 4.79 (d, J=11.4 Hz, 1H, PhCH2O), 4.71–4.64 (m, 4H, PhCH2O), 4.54 (d, J=12.4 Hz, 1H, PhCH2O), 4.50 (d, J=12.4 Hz, 1H, PhCH2O), 4.45 (d, J=10.5 Hz, 1H, PhCH2O), 4.43 (d, J=12.4 Hz, 1H, PhCH2O), 4.17–4.11 (m, 2H), 4.03 (t, J=9.4 Hz, 1H), 3.87 (t, J=9.4 Hz, 1H), 3.68 (t, J=9.6 Hz, 1H), 3.59 (dd, J=9.6 Hz, J=3.2 Hz, 1H), 3.56 (dd, J=9.8 Hz, J=3.4 Hz, 1H), 3.53–3.44 (m, 3H), 3.36 (d, J=10.1 Hz, 1H), 2.38 (d, J=2.3 Hz, 1H); 13C-NMR (100 MHz, CDCl3) δ: 138.9, 138.9, 138.4, 138.2, 138.1, 138.0, 137.9, 128.6, 128.5, 128.4, 128.1, 128.0, 128.0, 127.8, 127.8, 127.8, 127.7, 127.7, 127.6, 127.6, 127.4, 94.5, 94.4, 81.9, 81.1, 79.4, 79.1, 77.7, 75.7, 75.4, 75.2, 73.7, 73.6, 72.8, 72.5, 70.9, 70.7, 70.6, 69.2, 68.2; HR-MS (ESI) Anal. Calcd for C61H64O11K m/z 1101.4080 [M+K]+. Found 1101.4067. (2R,3R,4S,5R,6R)-4,5-Bis(benzyloxy)-2-((benzyloxy)m e t hy l ) - 6 - (((2 R , 3R , 5R , 6 R) - 3 , 4 - b i s ( b e n z y l ox y) - 6 ((benzyloxy)methyl)-5-((3-methylbut-2-en-1-yl)oxy)tetrahydro-2H-pyran-2-yl)oxy)tetrahydro-2H-pyran-3-ol (7) and (2R,3R,4S,5R,6R)-3,4,5-Tris(benzyloxy)-2-((benzyloxy)m e t hy l ) - 6 - (((2 R , 3R , 5R , 6 R) - 3 , 4 - b i s ( b e n z y l ox y) - 6 ((benzyloxy)methyl)-5-((3-methylbut-2-en-1-yl)oxy)tetrahydro-2H-pyran-2-yl)oxy)tetrahydro-2H-pyran (11) To 5 (105 mg, 0.119 mmol) was dissolved in 2 mL of DMF at 0°C were added NaH (12.0 mg, 60% dispersion in mineral oil, 0.300 mmol), TBAI (2.0 mg, 5.41 µmol) and prenyl bromide (15.1 µL, 0.131 mmol) sequentially. After stirring for 12 h at room temperature, MeOH (0.1 mL) was added and stirred for 5 min. Distilled water (10 mL) and CH2Cl2 (10 mL) were added to the mixture, and the organic layer was separated. Then, the organic layer was washed with hydrochloric acid (1 M, 5 mL), saturated aqueous NaHCO3 solution (5 mL), dried over anhydrous Na2SO4 and concentrated. The resultant crude material was purified by silica gel column chromatography (n-hexane : ethyl acetate=5 : 1) to give a compound 7 (50.0 mg, 44%) as a colorless syrup. Compound 11 was synthesized using the same procedure as that for 7. Compound 6 (106 mg, 0.109 mmol) was used as the substrate, NaH (8.7 mg, 60% dispersion in mineral oil, 0.218 mmol), TBAI (2.0 mg, 5.41 µmol) and prenyl bromide (62.9 µL, 0.544 mmol) were used to afford 11 (115 mg, 0.109 mmol, quantitative yield) as a colorless syrup. 7: [α]D19 +88 (c=1.0, CHCl3); IR (CHCl3) ν: 3576, 3010, 2925, 2868, 1454, 1362, 1221, 1098, 997, 698 cm−1; 1H-NMR (400 MHz, CDCl3) δ: 7.31–7.12 (m, 30H), 5.19–5.16 (m, 1H), 5.13 (br s, 2H), 4.93 (d, J=11.2 Hz, 1H, PhCH2O), 4.90 (d, J=11.2 Hz, 1H, PhCH2O), 4.79 (d, J=11.2 Hz, 1H, PhCH2O), 4.70 (d, J=11.2 Hz, 1H, PhCH2O), 4.62–4.54 (m, 4H, PhCH2O), 4.47 (d, J=12.2 Hz, 1H, PhCH2O), 4.41 (d, J=12.2 Hz, 1H, PhCH2O), 4.36 (d, J=12.2 Hz, 1H, PhCH2O), 4.34 (d, J=12.2 Hz, 1H, PhCH2O), 4.24–4.19 (m, 1H), 4.08–4.03 (m, 2H), 3.95–3.88 (m, 2H), 3.77 (t, J=9.4 Hz, 1H), 3.59 (t, J=9.4 Hz, 1H), 3.48–3.39 (m, 5H), 3.37–3.12 (m, 2H), 2.30 (br s, 1H), 1.62 (s, 3H), 1.46 (s, 3H); 13C-NMR (100 MHz, CDCl3) δ: 139.0, 138.9, 138.3, 138.1, 138.0, 138.0, 137.1,
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128.6, 128.4, 128.0, 127.9, 127.9, 127.8, 127.7, 127.6, 127.6, 127.6, 127.5, 121.2, 94.7, 94.6, 81.8, 81.3, 79.3, 79.0, 75.6, 75.5, 73.6, 73.6, 72.8, 72.4, 70.9, 70.8, 70.5, 69.7, 69.2, 68.4, 25.9, 18.0; HR-MS (ESI) Anal. Calcd for C59H66O11K m/z 989.4237 [M+K]+. Found 989.4210. 11: [α]D20 +87 (c=1.6, CHCl3); IR (CHCl3) ν: 3068, 3010, 2926, 2868, 2366, 1454, 1362, 1099, 995, 698 cm−1; 1H-NMR (400 MHz, CDCl3) δ: 7.38–7.20 (m, 33H), 7.12–7.09 (m, 2H), 5.26–5.24 (m, 1H), 5.21–5.20 (m, 2H), 4.99 (d, J=10.8 Hz, 1H, PhCH2O), 4.97 (d, J=11.0 Hz, 1H, PhCH2O), 4.86 (d, J=10.8 Hz, 1H, PhCH2O), 4.84 (d, J=11.0 Hz, 1H, PhCH2O), 4.80 (d, J=10.5 Hz, 1H, PhCH2O), 4.70–4.62 (m, 4H, PhCH2O), 4.56 (d, J=12.1 Hz, 1H, PhCH2O), 4.54 (d, J=12.2 Hz, 1H, PhCH2O), 4.44 (d, J=12.1 Hz, 1H, PhCH2O), 4.43 (d, J=10.5 Hz, 1H, PhCH2O), 4.35 (d, J=12.2 Hz, 1H, PhCH2O), 4.33–4.27 (m, 1H), 4.17–4.13 (m, 2H), 3.99 (t, J=9.4 Hz, 2H), 3.96 (t, J=9.4 Hz, 1H), 3.69–3.65 (m, 1H), 3.58–3.47 (m, 5H), 3.41 (d, J=10.8 Hz, 1H), 3.33 (d, J=10.8 Hz, 1H), 1.69 (s, 3H), 1.53 (s, 3H); 13C-NMR (100 MHz, CDCl3) δ: 139.1, 139.0, 138.4, 138.4, 138.3, 138.0, 138.0, 137.2, 128.5, 128.5, 128.4, 128.4, 128.1, 128.1, 128.0, 128.0, 127.8, 127.7, 127.6, 127.6, 127.6, 127.5, 121.3, 94.8, 82.0, 81.8, 79.4, 79.4, 77.7, 77.5, 77.4, 75.8, 75.7, 75.2, 73.6, 72.8, 72.7, 70.8, 70.6, 69.7, 68.4, 68.1, 25.9, 18.1; HR-MS (ESI) Anal. Calcd for C66H72O11Na m/z 1063.4967 [M+Na]+. Found 1063.4945. (2S)-1-(((2R,3R,5R,6R)-4,5-Bis(benzyloxy)-2-((benzyloxy)methyl) - 6 - (((2R, 3R,4S, 5R,6R) -3,4 -bis( benz yloxy) - 6 ((benzyloxy)methyl)-5-hydroxytetrahydro-2H-pyran-2-yl)oxy)tetrahydro-2H-pyran-3-yl)oxy)-3-methylbutane-2,3diol (8) and (2S)-1-(((2R,3R,5R,6R)-4,5-Bis(benzyloxy)2-((benzyloxy) methyl)-6-(((2R,3R,4S,5R,6R)-3,4,5-tris(benzyloxy)-6-((benzyloxy)methyl) tetrahydro-2H-pyran2-yl) oxy)tetrahydro-2H-pyran-3-yl) oxy)-3-methylbutane2,3-diol (12) AD-mix-α (118 mg), (DHQ)2PHAL (8.8 mg, 11.3 µmol) and methane sulfonamide (8.5 mg, 89.4 µmol) were dissolved in 1.8 mL of a mixed solvent of t-BuOH and H2O (1 : 1). The resulting solution was stirred for 30 min at room temperature and then cooled to 0°C. To the solution, 7 (42.8 mg, 42.5 µmol) in 0.8 mL of acetone was added and stirred for 66 h at 0°C. The reaction was quenched by Na2SO3 with stirring for 30 min at 0°C, and the mixture was extracted with EtOAc. The organic layer was washed with brine, dried over anhydrous Na2SO4 and concentrated. The diastereomeric ratio was determined to be 9 : 1 by 1H-NMR analysis. The crude material was purified by silica gel column chromatography (n-hexane : EtOAc=3 : 1) to give a compound 8 (44.5 mg, 45.0 µmol, quantitative yield) as a colorless syrup. Compound 12 was synthesized using the same procedure as that for 8. Compound 11 (46.9 mg, 45.0 µmol) was used as the raw material, AD-mix-α (124 mg), (DHQ)2PHAL (9.2 mg, 11.8 µmol) and methane sulfonamide (8.9 mg, 93.6 µmol) were used to afford 12 (21.9 mg, 20.4 µmol, 45%) as a colorless syrup. 8: [α]D25 +88 (c=1.6, CHCl3); IR (CHCl3) ν: 3573, 3066, 2931, 2870, 2364, 1454, 1221, 1098, 731, 699 cm−1; 1H-NMR (400 MHz, CDCl3) δ: 7.40–7.22 (m, 30H), 5.22 (d, J=3.7 Hz, 1H), 5.20 (d, J=3.9 Hz, 1H), 5.03 (d, J=11.2 Hz, 1H, PhCH2O), 5.02 (d, J=11.0 Hz, 1H, PhCH2O), 4.83 (d, J=11.2 Hz, 1H, PhCH2O), 4.78 (d, J=11.0 Hz, 1H, PhCH2O), 4.70 (d, J=11.9 Hz, 1H, PhCH2O), 4.70–4.66 (m, 2H, PhCH2O), 4.62 (d, J=11.9 Hz, 1H, PhCH2O), 4.52 (d, J=12.1 Hz, 1H), 4.51 (d,
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J=12.1 Hz, 1H), 4.44 (d, J=12.1 Hz, 1H), 4.40 (d, J=12.1 Hz, 1H), 4.12 (br dt, J=9.8, 3.4 Hz, 1H), 4.04 (br dt, J=10.0, 2.5 Hz, 1H), 3.95–3.92 (m, 1H), 3.90–3.87 (m, 1H), 3.83 (dd, J=10.0, 2.3 Hz, 1H), 3.73–3.67 (m, 1H), 3.60–3.56 (m, 2H), 3.55–3.53 (m, 1H), 3.51–3.47 (m, 3H), 3.44–3.39 (m, 2H), 3.33 (dd, J=11.0, 2.1 Hz, 1H), 3.00 (d, J=3.9 Hz, 1H), 2.44 (d, J=2.5 Hz, 1H), 2.42 (br s, 1H), 1.10 (s, 3H), 0.99 (s, 3H); 13C-NMR (100 MHz, CDCl3) δ: 138.8, 138.5, 138.1, 138.0, 137.6, 128.7, 128.5, 128.5, 128.5, 128.1, 128.0, 127.9, 127.9, 127.8, 127.8, 127.8, 127.6, 127.4, 94.4, 94.2, 81.3, 81.2, 79.6, 79.2, 78.1, 76.3, 75.7, 75.4, 73.8, 73.7, 73.7, 72.7, 72.7, 71.3, 70.9, 70.7, 70.6, 69.3, 68.5, 26.6, 24.6; HR-MS (ESI) Anal. Calcd for C59H68O13Na m/z 1007.4552 [M+Na]+. Found 1007.4525. 12: [α]D26 +88 (c=0.38, CHCl3); IR (CHCl3) ν: 3566, 2921, 2869, 2360, 1455, 1099, 997, 721, 698 cm−1; 1H-NMR (400 MHz, CDCl3) δ: 7.38–7.13 (m, 33H), 7.12–7.09 (m, 2H), 5.20 (d, J=3.4 Hz, 1H), 5.19 (d, J=3.4 Hz, 1H), 5.02 (d, J=10.8 Hz, 1H, PhCH2O), 5.01 (d, J=10.8 Hz, 1H, PhCH2O), 4.89 (d, J=10.8 Hz, 1H, PhCH2O), 4.81 (d, J=10.5 Hz, 1H, PhCH2O), 4.77 (d, J=10.8 Hz, 1H, PhCH2O), 4.72 (d, J=12.1 Hz, 1H, PhCH2O), 4.68–4.61 (m, 2H, PhCH2O), 4.64 (d, J=12.1 Hz, 1H, PhCH2O), 4.54 (d, J=12.1 Hz, 1H), 4.53 (d, J=12.1 Hz, 1H), 4.45 (d, J=10.5 Hz, 1H), 4.40 (d, J=12.1 Hz, 1H), 4.37 (d, J=12.1 Hz, 1H), 4.15 (br dt, J=9.8, 3.4 Hz, 1H), 4.14–4.06 (m, 2H), 3.91 (t, J=9.4 Hz, 1H), 3.82 (dd, J=9.4, 2.3 Hz, 1H), 3.69 (t, J=9.4 Hz, 1H), 3.60 (dd, J=9.6, 3.4 Hz, 1H), 3.54 (dd, J=9.4, 3.6 Hz, 1H), 3.52 (dd, J=9.4, 3.6 Hz, 1H), 3.49 (dd, J=9.6, 8.0 Hz, 2H), 3.44–3.41 (m, 1H), 3.41–3.39 (m, 1H), 3.37 (dd, J=10.8, 1.8 Hz, 1H), 3.32 (dd, J=10.8, 2.3 Hz, 1H), 3.00 (d, J=3.9 Hz, 1H), 2.40 (s, 1H), 1.10 (s, 3H), 0.98 (s, 3H); 13C-NMR (100 MHz, CDCl3) δ: 138.9, 138.6, 138.4, 138.3, 138.1, 137.9, 137.7, 128.5, 128.5, 128.5, 128.1, 128.1, 128.0, 127.9, 127.9, 127.8, 127.8, 127.8, 127.8, 127.7, 127.5, 127.5, 94.6, 94.4, 82.0, 81.3, 79.6, 79.6, 78.2, 77.8, 76.3, 75.7, 75.7, 75.3, 73.8, 73.7, 73.6, 73.0, 72.6, 71.3, 70.8, 70.5, 68.5, 68.2, 26.6, 24.6; HR-MS (ESI) Anal. Calcd for C66H74O13Na m/z 1097.5022 [M+Na]+. Found 1097.4999. (S)-2-(2-(Benzyloxy)propan-2-yl)oxirane (9) To (S)-2(oxiran-2-yl)propan-2-ol prerared according to the known method8) (25.9 mg, 0.254 mmol) in THF (1.0 mL) at 0°C were added TBAI (7.8 mg, 21.1 µmol) and NaH (31.7 mg, 60% dispersion in mineral oil, 0.792 mmol), which was followed by slow addition of BnBr (78.4 µL, 0.659 mmol). After stirring for 24 h at the same temperature, MeOH (0.1 mL) was added and extracted with CH2Cl2. The combined organic layers were washed with hydrochloric acid (1 M) and saturated aqueous NaHCO3, dried over anhydrous Na2SO4, and concentrated. The resulting residue was purified by silica gel column chromatography (n-hexane : EtOAc=70 : 1 to 40 : 1) to afford 9 (32.8 mg, 0.170 mmol, 67%) as a colorless oil; [α]D26 +4.8 (c=0.71, CHCl3); IR (CHCl3) ν: 3648, 2985, 2361, 1455, 1363, 1225, 1161, 897, 697 cm−1; 1H-NMR (400 MHz, CDCl3) δ: 7.36–7.26 (m, 5H), 4.61 (d, J=11.2 Hz, 1H), 4.55 (d, J=11.2 Hz, 1H), 3.07 (dd, J=4.0 Hz, 2.8 Hz, 1H), 2.74–2.72 (m, 1H), 2.63 (dd, J=4.0, 4.8 Hz, 1H), 1.29 (s, 3H), 1.23 (s, 3H); 13C-NMR (100 MHz, CDCl3) δ: 139.5, 128.5, 74.4, 65.4, 57.8, 43.6, 23.5, 21.0. (2S)-3-(Benzyloxy)-1-(((2R,3R,5R,6R)-4,5-bis(benzyloxy)2 - (( ben z ylox y)methyl) - 6 - (((2 R, 3R, 4 S, 5R, 6R) -3, 4 , 5 tris(benzyloxy)- 6 -((benzyloxy)methyl)tetrahydro-2Hpyran-2-yl)oxy)tetrahydro-2H-pyran-3-yl)oxy)-3-methylbu-
tan-2-ol (10) To 6 (25.0 mg, 25.7 µmol) in 1.5 mL of DMF at 0°C were added NaH (2.6 mg, 60% dispersion in mineral oil, 65.0 µmol), 15-crown-5 (13 µL, 65.7 µmol) and 9 (12.3 mg, 64.0 µmol) sequentially. After stirring for 18 h at 70°C, 0.1 mL of MeOH was added, which was followed by stirring for 5 min. Distilled water (8 mL) and CH2Cl2 (10 mL) were added and separated. The organic layer was washed with hydrochloric acid (1 M, 4 mL), saturated aqueous NaHCO3 solution (5 mL), dried over anhydrous Na2SO4 and concentrated. The resultant crude material was purified by silica gel column chromatography (n-hexane : EtOAc=3 : 1) to give 10 (9.0 mg, 7.72 µmol, 30%) as a colorless syrup; [α]D24 +73 (c=0.37, CHCl3); IR (CHCl3) ν: 3568, 3063, 2926, 2862, 2331, 1454, 1363, 1099, 997, 778, 698 cm−1; 1H-NMR (400 MHz, CDCl3) δ: 7.41–7.24 (m, 36H), 7.14–7.11 (m, 2H), 5.20 (d, J=3.4 Hz, 2H), 5.02 (d, J=11.0 Hz, 1H), 5.00 (d, J=10.5 Hz, 1H), 4.88 (d, J=11.0 Hz, 1H), 4.87 (d, J=10.5 Hz, 1H), 4.82 (d, J=10.5 Hz, 1H), 4.71–4.64 (m, 4H), 4.55 (d, J=12.1 Hz, 1H), 4.49 (d, J=11.9 Hz, 1H), 4.47 (d, J=10.5 Hz, 1H), 4.44–4.42 (m, 2H), 4.42 (d, J=11.9 Hz, 1H), 4.37 (d, J=12.1 Hz, 1H), 4.18–4.06 (m, 2H), 4.03 (t, J=9.4 Hz, 1H), 4.00 (t, J=9.4 Hz, 1H), 3.97–3.93 (m, 1H), 3.85 (dd, J=10.3, 1.6 Hz, 1H), 3.75–3.63 (m, 3H), 3.58–3.46 (m, 5H), 3.42–3.34 (m, 2H), 1.14 (s, 3H), 1.12 (s, 3H); 13C-NMR (100 MHz, CDCl3) δ: 139.4, 138.9, 138.7, 138.3, 138.2, 138.1, 137.9, 137.8, 128.5, 128.4, 128.3, 128.3, 128.0, 127.9, 127.8, 127.7, 127.6, 127.6, 127.5, 127.5, 127.5, 127.4, 127.2, 127.2, 94.6, 94.5, 81.8, 81.3, 79.5, 79.4, 78.4, 77.7, 76.4, 75.9, 75.6, 75.5, 75.1, 74.1, 73.5, 72.7, 72.6, 70.8, 70.7, 70.6, 68.4, 68.1, 63.7, 29.7, 21.8; HR-MS (ESI) Anal. Calcd for C73H80O13Na m/z 1187.5491 [M+Na]+. Found 1187.5476. Lentztrehalose A (1) from 8 To 8 (28.0 mg, 28.4 µmol) in 2 mL of MeOH was added 10% palladium carbon (Pd/C, 20 mg), and the resulting suspension was stirred under atmospheric pressure of H2 at room temperature for 24 h. After removal of the catalyst by filtration on a pad of Celite, the filtrate was concentrated to dryness to give lenztrehalose A (1, 12.6 mg, 28.4 µmol, quantitative yield) as a white solid; [α]D25 +147 (c=0.65, MeOH); IR (CHCl3) ν: 3584, 2928, 1411, 1040, 696 cm−1; 1H-NMR (400 MHz, CD3OD) δ: 5.10 (d, J=3.8 Hz, 1H), 5.08 (d, J=3.9 Hz, 1H), 4.02 (dd, J=10.5, 2.7 Hz, 1H), 3.90 (t, J=9.4 Hz, 1H), 3.84 (br dt, J=9.4, 2.8 Hz, 1H), 3.80–3.76 (m, 5H), 3.67 (dd, J=11.7, 4.4 Hz, 1H), 3.66–3.63 (m, 1H), 3.54 (dd, J=7.8, 2.5 Hz, 1H), 3.49 (dd, J=9.6, 3.8 Hz, 1H), 3.46 (dd, J=9.6, 3.8 Hz, 1H), 3.31 (t, J=9.4 Hz, 1H), 3.28 (t, J=9.4 Hz, 1H), 1.19 (s, 3H), 1.17 (s, 3H); 13C-NMR (100 MHz, CD3OD) δ: 95.1, 95.0, 80.4, 78.1, 74.7, 74.5, 74.4, 73.8, 73.4, 73.2, 72.8, 72.7, 71.9, 62.6, 62.1, 26.5, 25.4; HR-MS (ESI) Anal. Calcd for C17H32O13Na m/z 467.1735 [M+Na]+. Found 467.1725. Lentztrehalose A (1) from 10 To 10 (8.5 mg, 7.29 µmol) in 1 mL of MeOH was added 10% Pd/C (7.0 mg), and the resulting suspension was stirred under atmospheric pressure of H2 at room temperature for 24 h. After removal of the catalyst by filtration on a pad of Celite, the filtrate was concentrated to dryness to give lenztrehalose A (1, 2.9 mg, 6.53 µmol, 89%) as a white solid. (S)-MTPA Ester (13) and (R)-MTPA Ester (14) To 12 (11.0 mg, 10.2 µmol) in 1 mL of CH2Cl2 were added (R)-MTPACl ((R)-α-methoxy-α-trifluoromethylphenylacetyl chloride, 10.0 mg, 39.6 µmol), TEA (11.4 µL, 81.8 µmol) and 4-dimethylaminopyridine (DMAP, 10.0 mg, 81.9 µmol), and the mixture was stirred at room temperature for 24 h. After removal of the
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solvents under reduced pressure, the residue was purified by silica gel column chromatography (n-hexane : EtOAc=3 : 1) to give the (S)-MTPA ester 13 (11.3 mg, 8.75 µmol, 86%) as a colorless syrup. (R)-MTPA ester was prepared using the same procedure with that of (S)-MTPA ester. Compound 12 (5.0 mg, 4.65 µmol), (S)-MTPA-Cl ((S)-α-methoxy-α-trifluoromethylphenylacetyl chloride, 4.5 mg, 17.8 µmol), TEA (5.2 µL, 37.3 µmol), and DMAP (4.5 mg, 36.8 µmol) were used to afford (R)-MTPA ester (14, 5.5 mg, 4.26 µmol, 92%) as a colorless syrup. (2S)-1-(((2R,3R,5R,6R)-4,5-Bis(benzyloxy)-2-((benzyloxy)methyl) - 6 - (((2R, 3R,4S, 5R,6R) -3,4, 5 -tris(benzyloxy) 6 -((benzyloxy)methyl)tetrahydro-2H-pyran-2-yl) oxy)tetrahydro-2H-pyran-3-yl)oxy)-3-hydroxy-3-methylbutan2-yl (2S)-3,3,3-Trifluoro-2-methoxy-2-phenylpropanoate (13) [α]D25 +68 (c=0.47, CHCl3); IR (CHCl3) ν: 3030, 2928, 2863, 2351, 2338, 1748, 1454, 1101, 698 cm−1; 1H-NMR (400 MHz, CDCl3) δ: 7.55 (d, J=8.0 Hz, 2H), 7.40–7.18 (m, 36H), 7.11–7.09 (m, 2H), 5.21 (d, J=3.6 Hz, 1H), 5.17 (d, J=3.6 Hz, 1H), 5.09 (dd, J=8.4, 4.2 Hz, 1H), 5.06 (d, J=11.4 Hz, 1H, PhCH2O), 5.00 (d, J=10.8 Hz, 1H, PhCH2O), 4.88 (d, J=10.8 Hz, 1H, PhCH2O), 4.82 (d, J=11.4 Hz, 1H, PhCH2O), 4.79 (d, J=10.8 Hz, 1H, PhCH2O), 4.68 (s, 2H, PhCH2O), 4.66–4.64 (m, 2H, PhCH2O), 4.51 (d, J=12.0 Hz, 1H, PhCH2O), 4.50 (d, J=12.0 Hz, 1H, PhCH2O), 4.44 (d, J=11.4 Hz, 1H, PhCH2O), 4.40 (d, J=12.0 Hz, 1H, PhCH2O), 4.34 (d, J=12.0 Hz, 1H, PhCH2O), 4.13 (br dt, J=10.2, 2.4 Hz, 1H), 4.02 (br dt, J=10.2, 2.4 Hz, 1H), 4.01 (t, J=9.6 Hz, 1H), 3.88 (t, J=9.6 Hz, 1H), 3.87 (dd, J=9.6, 3.6 Hz, 1H, H1 in Chart 2), 3.67 (t, J=9.6 Hz, 1H), 3.64 (dd, J=10.2, 8.4 Hz, 1H, H2 in Chart 2), 3.58 (dd, J=9.6, 3.6 Hz, 1H), 3.54 (dd, J=9.6, 3.6 Hz, 1H), 3.49 (t, J=9.6 Hz, 1H), 3.46 (dd, J=9.6, 3.6 Hz, 1H), 3.41 (s, 3H), 3.40 (t, J=2.4 Hz, 2H), 3.31 (dd, J=9.6, 3.6 Hz, 1H), 1.00 (s, 3H, H3 in Chart 2), 0.96 (s, 3H, H4 in Chart 2); 13CNMR (100 MHz, CDCl3) δ: 166.2, 139.1, 138.9, 138.4, 138.1, 138.0, 137.9, 137.8, 131.7, 129.6, 128.4, 128.3, 128.3, 128.0, 127.9, 127.8, 127.8, 127.7, 127.7, 127.6, 127.6, 127.6, 127.5, 127.5, 127.3, 95.1, 94.7, 81.8, 81.4, 80.6, 79.4, 79.1, 78.4, 77.7, 77.0, 75.5, 75.3, 75.0, 73.5, 73.4, 72.8, 72.5, 71.2, 71.1, 70.6, 70.5, 68.2, 68.1, 55.2, 25.6, 25.4; 19F-NMR (376 MHz, CDCl3) δ −86.7; HR-MS (ESI) Anal. Calcd for C76H81O15F3K m/z 1329.5159 [M+K]+. Found 1329.5114. (2R)-1-(((2R,3R,5R,6R)-4,5-Bis(benzyloxy)-2-((benzyloxy)methyl)-6-(((2R,3R,4S,5R,6R)-3,4,5-tris(benzyloxy)-6((benzyloxy)methyl)tetrahydro-2H-pyran-2-yl)oxy)tetrahydro-2H-pyran-3-yl)oxy)-3-hydroxy-3-methylbutan-2-yl (2S)-3,3,3-Trifluoro-2-methoxy-2-phenylpropanoate (14) [α]D25 +60 (c=0.27, CHCl3); IR (CHCl3) ν: 3019, 2925, 2862, 2362, 2335, 1746, 1563, 1221, 1162, 1100, 997, 706 cm−1; 1 H-NMR (400 MHz, CDCl3) δ: 7.55 (d, J=8.0 Hz, 2H), 7.39–7.19 (m, 36H), 7.11–7.10 (m, 2H), 5.23 (d, J=3.6 Hz, 1H),
Vol. 63, No. 11 (2015)
5.19 (d, J=3.6 Hz, 1H), 5.10 (dd, J=8.4, 4.2 Hz, 1H), 5.07 (d, J=11.4 Hz, 1H, PhCH2O), 4.99 (d, J=10.8 Hz, 1H, PhCH2O), 4.86 (d, J=10.8 Hz, 1H, PhCH2O), 4.82 (d, J=11.4 Hz, 1H, PhCH2O), 4.79 (d, J=10.8 Hz, 1H, PhCH2O), 4.68 (s, 2H, PhCH2O), 4.66–4.64 (m, 2H, PhCH2O), 4.51 (d, J=12.0 Hz, 1H, PhCH2O), 4.50 (d, J=12.0 Hz, 1H, PhCH2O), 4.44 (d, J=11.4 Hz, 1H, PhCH2O), 4.39 (d, J=12.0 Hz, 1H, PhCH2O), 4.34 (d, J=12.0 Hz, 1H, PhCH2O), 4.15 (br dt, J=10.2, 2.4 Hz, 1H), 4.10 (br dt, J=10.2, 2.4 Hz, 1H), 4.02 (t, J=9.6 Hz, 1H), 3.91 (dd, J=9.6, 3.6 Hz, 1H, H1 in Chart 2), 3.90 (t, J=9.6 Hz, 1H), 3.72 (dd, J=10.2, 8.4 Hz, 1H, H2 in Chart 2), 3.67 (t, J=9.6 Hz, 1H), 3.59 (dd, J=9.6 Hz, 3.6 Hz, 1H), 3.57 (dd, J=9.6, 3.6 Hz, 1H), 3.53, (t, J=9.6 Hz, 1H), 3.49 (dd, J=9.6, 3.6 Hz, 1H), 3.46 (t, J=2.4 Hz, 2H), 3.45 (s, 3H), 3.31 (dd, J=9.6, 3.6 Hz, 1H), 0.94 (s, 3H, H3 in Chart 2), 0.88 (s, 3H, H4 in Chart 2); 13C-NMR (100 MHz, CDCl3) δ: 166.3, 139.1, 138.9, 138.3, 138.1, 138.0, 137.8, 137.8, 132.3, 129.6, 128.4, 128.4, 128.3, 128.0, 127.9, 127.8, 127.7, 127.7, 127.7, 127.6, 127.5, 127.5, 127.5, 127.4, 95.2, 94.8, 81.9, 81.4, 80.6, 79.5, 79.2, 78.7, 77.7, 77.0, 75.5, 75.4, 75.1, 73.5, 73.5, 72.7, 72.5, 71.2, 71.1, 70.6, 70.5, 68.4, 68.1, 55.4, 25.6, 25.4; 19F-NMR (376 MHz, CDCl3) δ −86.6; HR-MS (ESI) Anal. Calcd for C76H81O15F3K m/z 1329.5159 [M+K]+. Found 1329.5107. Acknowledgment The authors thank Dr. Ryuichi Sawa, Ms. Yumiko Kubota, and Ms. Yuko Takahashi (BIKAKEN) for collection of spectral data. Conflict of Interest interest.
The authors declare no conflict of
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