molecules Article
Efficient Synthesis and Bioactivity of Novel Triazole Derivatives Boyang Hu, Hanqing Zhao *, Zili Chen, Chen Xu, Jianzhuang Zhao and Wenting Zhao Key Laboratory of Urban Agriculture (North China), Ministry of Agriculture, College of Biological Science and Engineering, Beijing University of Agriculture, Beijing 102206, China;
[email protected] (B.H.);
[email protected] (Z.C.);
[email protected] (C.X.);
[email protected] (J.Z.);
[email protected] (W.Z.) * Correspondence:
[email protected]; Tel.: +86-10-8079-9234; Fax: +86-10-8079-9234 Received: 25 February 2018; Accepted: 15 March 2018; Published: 21 March 2018
Abstract: Triazole pesticides are organic nitrogen-containing heterocyclic compounds, which contain 1,2,3-triazole ring. In order to develop potential glucosamine-6-phosphate synthase (GlmS) inhibitor fungicides, forty compounds of triazole derivatives were synthesized in an efficient way, thirty nine of them were new compounds. The structures of all the compounds were confirmed by high resolution mass spectrometer (HRMS), 1 H-NMR and 13 C-NMR. The fungicidal activities results based on means of mycelium growth rate method indicated that some of the compounds exhibited good fungicidal activities against P. CapasiciLeonian, Sclerotinia sclerotiorum (Lib.) de Bary, Pyricularia oryzae Cav. and Fusarium oxysporum Schl. F.sp. vasinfectum (Atk.) Snyd. & Hans. at the concentration of 50 µg/mL, especially the inhibitory rates of compounds 1-d and 1-f were over 80%. At the same time, the preliminary studies based on the Elson-Morgan method indicated that the compounds exhibited some inhibitory activity toward glucosamine-6-phosphate synthase (GlmS). These compounds will be further studied as potential antifungal lead compounds. The structure-activity relationships (SAR) were discussed in terms of the effects of the substituents on both the benzene and the sugar ring. Keywords: triazole pesticide; carbohydrates; synthesis; fungicidal activity
1. Introduction Carbohydrates play an important role in the field of pesticide investigation, and many natural carbohydrate products used as pesticides have shown great vitality [1]. Carbohydrate compounds are easy to degrade, have good environmental compatibility [2], and are less resistant to resistance [3]. The new fungicides, which were developed based on carbohydrate compounds, have advantages of safety, high efficiency, low residue and not easy to generate insecticide resistance [4,5], not only ensuring the high yield of vegetables and other agricultural products [6], but also solve the problem of pesticide residues. Triazole pesticides are the most widely used variety of fungicides in agricultural production, which are mainly divided into fungicides, herbicides, pesticides and plant growth regulators [7]. At this stage, there are more than 30 varieties which have been produced and widely used, such as triazole alcohol [8], triazolone, propiconazole [9], hexaconazole [10] and fluorosilazole [11]. Triazole compounds have been extensively studied in the field of medicine and pesticides, and exhibit a variety of biological activities. In addition to a strong internal fungicidal activity, triazole compounds also have a regulatory role in the growth of plant [12], herbicidal [13], insecticidal [14] and antifungal [15,16]. Because of these multiple effect of the triazole structure, the research of these compounds have been in the ascendant so far. In order to obtain more efficient derivatives, the chemical structure modification of
Molecules 2018, 23, 709; doi:10.3390/molecules23040709
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these compounds asmodification well as the research as medicine andas veterinary have been frontier issues chemical structure of compounds well the as and chemical structure modification of these these compounds as well as as drugs the research research as medicine medicine and both at home and abroad for a long time. veterinary drugs have been frontier issues both at home and abroad for a long time. veterinary drugs have been frontier issues both at home and abroad for a long time. Biorational design based basedon onspecific specifictarget target one of important means of international is one of important means of new Biorational design design based on specific target is is one of the thethe important means of international international new new pesticide creation. In the previous research ourlaboratory, laboratory, carbohydrate carbohydrate derivatives pesticide creation. In previous research in pesticide creation. In the the previous research ininour our laboratory, carbohydrate derivatives of of five-membered ring thiadiazole derivatives (I, Figure 1) were synthesized and their fungicidal five-membered ring thiadiazole derivatives derivatives Figure 1) were synthesized and their fungicidal activities The results results of activities were were studied studied as as well well [1]. [1]. The of bioactivity bioactivity determination determination showed showed that that some some compounds fungicidal activities against Sclerotinia sclerotiorum (Lib.) compounds exhibited exhibited good good fungicidal fungicidal activities activities against againstSclerotinia Sclerotiniasclerotiorum sclerotiorum (Lib.) (Lib.) de de Bary Bary and and Pyricularia their glucosamine-6-phosphate synthase (GlmS [17,18]; EC oryzae Cav. and consistent with their glucosamine-6-phosphate synthase (GlmS [17,18]; Pyriculariaoryzae oryzaeCav. Cav.and andconsistent consistentwith with their glucosamine-6-phosphate synthase (GlmS [17,18]; 2.6.1.16) inhibitory activities. EC inhibitory activities. EC 2.6.1.16) 2.6.1.16) inhibitory activities.
Figure Figure 1. 1. Structure Structure of of the the thiadiazole thiadiazole (I) (I) and and triazole triazole derivatives derivatives (1, (1, 2, 2, 3, 3, 4, 4, 5, 5, 6). 6).
ed fungicidpromising substrate ed better betterby fungicidpromising results, based on the structural characteristics of of the the substrate substrate Inspired these promising results, results, based based on on the the structural structural characteristics characteristics of the fructose-6-phosphate and the current research basis [1,19–21], we introduced the triazole fructose-6-phosphate and the current research basis [1,19–21], we introduced the triazole group fructose-6-phosphate and the current research basis [1,19–21], we introduced the triazole group group which which important bioactivities of in article, series of which possessed possessed various important bioactivities instead of thiadiazole thiadiazole in this this article, six series of possessed various various important bioactivities instead ofinstead thiadiazole in this article, six series ofsix novel furan novel furan glucosyl triazole compounds were designed and synthesized for the first time, their novel furan glucosyl triazole compounds were designed and synthesized for the first time, their glucosyl triazole compounds were designed and synthesized for the first time, their fungicidal activities fungicidal activities P. sclerotiorum Bary, Botrytis fungicidal activities against against P. CapasiciLeonian, CapasiciLeonian, Sclerotinia sclerotiorum (Lib.) de Bary, Botrytis cinerea cinerea against P. CapasiciLeonian, Sclerotinia sclerotiorumSclerotinia (Lib.) de Bary, Botrytis(Lib.) cinereade Pers, Pyricularia oryzae Pers, Pyricularia oryzae Cav., Fusarium oxysporum Schl. F.sp. vasinfectum (Atk.) Snyd. & Hans. and Pers, Pyricularia oryzae Cav., Fusarium oxysporum Schl. F.sp. vasinfectum (Atk.) Snyd. & Hans. and Cav., Fusarium oxysporum Schl. F.sp. vasinfectum (Atk.) Snyd. & Hans. and enzyme inhibitory activities enzyme inhibitory activities against Candida albicans GlmS were evaluated. We would like to report enzyme inhibitory activities against Candida albicans GlmS were evaluated. We would like to report against Candida albicans GlmS were evaluated. We would like to report their synthesis (Scheme 1) and their 1) bioactivities in much greater also structure-activity their synthesis synthesis (Scheme 1) and and bioactivities intheir much greater details, details, and and also their theirstudies. structure-activity bioactivities in (Scheme much greater details, and also structure-activity relationship We report relationship studies. report the relationship studies. We We report herein the preliminary preliminary results results of of the the study. study. herein the preliminary results ofherein the study.
Scheme 1. Cont.
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Scheme1.1.Synthesis Synthesisofofthe the target compounds 4, 5 6. and 6. Reagents and conditions: (a)orMeI or Scheme target compounds 1, 2,1,3,2,4,3,5 and Reagents and conditions: (a) MeI BnBr, ◦ 2CO3, DMF, r.t.;70% thenAcOH, 70% AcOH, 2 h; NaIO 2,2CH 2, r.t.; NaBH 4, EtOAc-H = 7: KBnBr, , DMF, r.t.; then 70 C,702 °C, h; NaIO , CH Cl22,Cl r.t.; NaBH = 7:3, 2 CO3K 4 -SiO42-SiO 4 , EtOAc-H 2 O2O 0 °C to r.t., 15 min; Tfpyridine, 2O, pyridine, to15 r.t., 15 then min, NaN then3NaN 3, DMF, 4 h; 7 (5 03,◦ C to r.t., 15 min; Tf2 O, 0 ◦ C0to°C r.t., min, , DMF, 60 ◦ C,60 4 h;°C, 62% for62% 7 (5for steps), 4·5H2O, ascorbate, sodium ascorbate, CH32Cl 2-CH OH-H 2O r.t., = 1:1:1, r.t., 1 h, steps), for 8 (5(b) steps); CuSO 65% for 65% 8 (5 steps); CuSO(b) CH2 Cl2 -CH OH-H = 1:1:1, 1 h, 69–92% 4 ·5H 2 O, sodium 2 3O ◦ C to r.t., for 1, 66–94% 2; (c) 90% 2 h,to60–81% 3, 73–88% 4; (d) Ac PDC, 0 °C r.t., 2 h,for 60–81% for 3,for 73–88% for2 O, 4; (d) Acr.t., 2O, 69–92% for 1,for 66–94% for 2;CF (c)3 COOH, 90% CF03COOH, 2PDC, h, 80–91% for80–91% 5, 82–89% 6. r.t., 2 h, for for 5, 82–89% for 6.
2. Results Results and and Discussion Discussion 2. 2.1. 2.1. Synthesis Synthesis of of the the Title TitleCompounds Compounds As envisioned that that the thetarget targetcompounds compoundstriazole triazolederivatives derivatives1,1,2,2,3,3,4,4,5 As shown shown in in Scheme 1, we envisioned 5and and6 6could could be synthesized from the intermediates 7 [22] and 8 [23] which be prepared be synthesized from the intermediates 7 [22] and 8 [23] which couldcould be prepared using using 1,2,5,6-di-isopropylideneD -glucose the starting material fiveaccording steps according to the 1,2,5,6-di-isopropylideneD-glucose as the as starting material for fivefor steps to the known known methods [22,23]. Then cyclization 7 and 8 with alkynethe provided the desired triazole1 methods [22,23]. Then cyclization of 7 and 8ofwith alkyne provided desired triazole derivatives derivatives andconditions 2 under the conditions of and copper sulfate and sodium in high yields, and 2 under1the of copper sulfate sodium ascorbate in highascorbate yields, respectively. Then respectively. Then the target 3 or 4by were prepared by treating compounds or 2 with 90% the target compounds 3 or compounds 4 were prepared treating compounds 1 or 2 with 90%1 trifluoroacetic trifluoroacetic acid.5Compounds 5 or 6 were obtained by compound 3 or 4. acid. Compounds or 6 were obtained by acetylation of acetylation compound of 3 or 4. All synthesized according to the procedures described in Scheme 1 in good Allthe thederivatives derivativeswere were synthesized according to the procedures described in Scheme 1 in yields of 60–98%. The structures of all theofsynthesized compounds were confirmed from its 1 H-NMR, good yields of 60–98%. The structures all the synthesized compounds were confirmed from its 13 1H-NMR, 13C-NMR 1H-NMR of C-NMR spectra andspectra HRMS. and The 1HRMS. H-NMRThe experiments compoundsof 1/2/5/6 were conducted in experiments compounds 1/2/5/6 were CDCl Nevertheless, because of thebecause poor solubility of compounds 3/4, so we had3/4, to conducted insolvent. CDCl3 as the solvent. Nevertheless, of the poor solubility of compounds 3 as the switch solvent to methanol-d data of compounds 4 or DMSO-d 6. the Thetarget physical data ofwere the given target so we the had to switch the solvent to methanol-d 4 or DMSO-d 6 . The physical in Table 1. were given in Table 1. compounds Table Table1.1.Physical PhysicalData Dataof ofCompounds Compounds1,1,2,2,3,3,4,4,55and and6.6.
Compd. Compd. 1-a1-a 1-b1-b 1-c1-c 1-d1-d 1-e1-e 1-f1-f 1-g 1-g 2-a [24] 2-a [24] 2-b 2-b2-c 2-c2-d 2-d2-e 2-e2-f 2-g 2-f 3-a 2-g3-b 3-a3-c 3-b 3-c 3-d 3-e 3-f
R1 R1 Me Me Me Me Me Me Me Me Me Me Me Me Me Me Bn Bn Bn Bn Bn Bn Bn Bn Bn Bn Bn Bn Bn Me Bn Me Me Me Me Me Me Me Me
R2 R2 6H5C C6 H5 -C66H H44-3-CH 3-CH33-C O-C66H444-CH33O-C 4-CH 4-F-C 4-F-C66H444-NO -C66H H44-4-NO22-C 4-Cl-C H44-4-Cl-C66H CH -CH(OH)CH33-CH(OH)C6 H5 5C6H 3-CH 3 -C6 H4 3 -C 3-CH 4-CH3 O-C66H H4-4 4-F-C H - 43O-C 6 4-CH 6 4H 4-NO 2 -C 6H 6H 4-4 4-F-C 4-Cl-C 6H 4 -42-C 6H 4-NO CH3 -CH(OH)4-Cl-C6H4C6 H5 3-CH(OH)CH 3-CH 3 -C6 H4 H5-6 H4 4-CHC3 6O-C 3-CH3-C6H44-CH3O-C6H44-F-C6H44-NO2-C6H44-Cl-C6H4-
Formula Formula
m.p./°C YieldYield StatusStatus m.p./◦ C (%) (%) C 17H21O4N3 White foamy solid 159.9–160.4 79.4 C17 H21 O4 N3 White foamy solid 159.9–160.4 79.4 C 18 H 23 O 4 N 3 Yellow foamy solid 108.0–109.7 79.6 C18 H23 O4 N3 Yellow foamy solid 108.0–109.7 79.6 C23 18H O35N3 WhiteWhite 156.6–157.5 69.3 69.3 C18 H O23 foamyfoamy solid solid 156.6–157.5 5N C17 H O20 foamyfoamy solid solid 121.4–122.3 C20 17H O34FN3F WhiteWhite 121.4–122.3 83.0 83.0 4N C17 H O20 foamyfoamy solid solid 126.5–126.8 6N C20 17H O46N4 WhiteWhite 126.5–126.8 77.1 77.1 C17 H O20 Cl3Cl WhiteWhite foamyfoamy solid solid 135.9–136.7 20H 4N C17 O34N 135.9–136.7 79.3 79.3 C13 H21 O5 N3 Yellow foamy solid 90.2–90.9 92.3 C13H21O5N3 Yellow foamy solid 90.2–90.9 92.3 C23 H25 O4 N3 White foamy solid 133.2–134.1 66.0 C 23H25O4N3 White foamy solid 133.2–134.1 C24 H27 O4 N3 White foamy solid 108.8–110.2 79.4 66.0 C 24 H 27 O 4 N 3 White foamy solid 108.8–110.2 C24 H27 O5 N3 White foamy solid 134.6–135.7 73.6 79.4 C23 HC2424O foamyfoamy solid solid 164.3–164.7 H427NO3 F 5N3 WhiteWhite 134.6–135.7 90.4 73.6 C23C H2324HO246O N44N3F YellowWhite foamyfoamy solid solid 182.6–183.6 164.3–164.7 90.3 90.4 C23 HC NO WhiteYellow foamy foamy solid solid 136.2–136.5 2423O 3 Cl H4 24 6N4 182.6–183.6 93.7 90.3 C19 H25 O5 N3 White foamy solid 90.6–90.9 87.6 C23H24O4N3Cl White foamy solid 136.2–136.5 93.7 C14 H17 O4 N3 White foamy solid 101.1–102.1 78.5 C 19H25O5N3 White foamy solid 90.6–90.9 87.6 C15 H19 O4 N3 Oily —— 77.4 C29 14H O4N3 WhiteWhite 101.1–102.1 79.4 78.5 C15 H O17 foamyfoamy solid solid 130.3–130.8 5 N3 C15H19O4N3 Oily —— 77.4 C15H29O5N3 White foamy solid 130.3–130.8 79.4 C14H16O4N3F White foamy solid 136.5–137.1 64.9 C14H16O6N4 White foamy solid 149.2–150.1 74.3 C14H16O4N3Cl White foamy solid 109.4–110.2 80.7
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Table 1. Cont. Compd.
R1
R2
Formula
Status
m.p./◦ C
Yield (%)
3-d 3-e 3-f 3-g 4-a 4-b 4-c 4-d 4-e 4-f 4-g 5-a 5-b 5-c 5-d 5-e 5-f 6-a 6-b 6-c 6-d 6-e 6-f
Me Me Me Me Bn Bn Bn Bn Bn Bn Bn Me Me Me Me Me Me Bn Bn Bn Bn Bn Bn
4-F-C6 H4 4-NO2 -C6 H4 4-Cl-C6 H4 CH3 -CH(OH)C6 H5 3-CH3 -C6 H4 4-CH3 O-C6 H4 4-F-C6 H4 4-NO2 -C6 H4 4-Cl-C6 H4 CH3 -CH(OH)C6 H5 3-CH3 -C6 H4 4-CH3 O-C6 H4 4-F-C6 H4 4-NO2 -C6 H4 4-Cl-C6 H4 C6 H5 3-CH3 -C6 H4 4-CH3 O-C6 H4 4-F-C6 H4 4-NO2 -C6 H4 4-Cl-C6 H4 -
C14 H16 O4 N3 F C14 H16 O6 N4 C14 H16 O4 N3 Cl C10 H16 O5 N3 C20 H21 O4 N3 C23 H21 O4 N3 C21 H23 O5 N3 C20 H20 O4 N3 F C20 H20 O6 N4 C20 H20 O4 N3 Cl C16 H21 O5 N3 C18 H21 O6 N3 C19 H23 O6 N3 C18 H20 O7 N3 C18 H20 O6 N3 F C18 H20 O8 N4 C18 H20 O6 N3 Cl C24 H25 O6 N3 C25 H27 O6 N3 C25 H27 O7 N3 C24 H24 O6 N3 F C24 H24 O8 N4 C24 H24 O6 N3 Cl
White foamy solid White foamy solid White foamy solid Oily White foamy solid White foamy solid Yellow foamy solid White foamy solid White foamy solid Yellow foamy solid White foamy solid White foamy solid White foamy solid White foamy solid White foamy solid Oily White foamy solid White foamy solid White foamy solid Yellow foamy solid White foamy solid Oily White foamy solid
136.5–137.1 149.2–150.1 109.4–110.2 —— 98.7–99.6 90.2–90.6 121.6–123.0 132.7–134.2 156.2–156.9 103.7–104.4 105.7–106.1 140.2–141.1 116.7–118.1 156.7–157.9 141.6–143.6 —— 131.3–133.0 148.0–149.3 110.7–112.5 140.6–141.9 123.8–124.9 —— 140.6–141.4
64.9 74.3 80.7 60.2 80.3 74.2 76.8 80.5 81.6 73.4 87.6 88.9 87.4 89.4 85.4 80.3 90.7 87.2 82.4 86.7 85.3 86.1 88.7
2.2. Fungicidal Activity of Compounds 1, 2, 3, 4, 5, 6 against Five Fungus Species Fungicidal activities of the target compounds 1, 2, 3, 4, 5, 6 against five fungal species were evaluated as previously reported [25] and compared with the commercial fungicide chlorothalonil. The inhibition rates were given in Table 2. The determination results showed that, most of the tested compounds displayed a certain degree of fungicidal activity against the five species at the concentration of 50 µg/mL. Table 2. Inhibition rate of target compounds against five fungus species (% control at 50 µg/mL). Inhibition Ratio (%) Compd. 1-a 1-b 1-c 1-d 1-e 1-f 1-g 2-a [24] 2-b 2-c 2-d 2-e 2-f 2-g 3-a 3-b 3-c 3-d 3-e 3-f 3-g 4-a 4-b
P. S. CapasiciLeonian sclerotiorum 60.7 61.3 60.7 80.1 82.5 81.2 40.2 48.2 65.3 59.8 76.6 84.9 86.5 50.1 40.1 35.6 38.9 50.2 44.7 46.8 23.1 21.2 29.6
70.2 69.4 71.5 87.6 83.9 85.1 49.2 66.6 69.0 62.8 88.1 82.5 85.3 43.9 30.3 28.4 31.5 38.4 39.6 25.3 13.7 26.4 29.9
B. cinerea
Pyricularia oryzae Cav.
Fusarium oxysporum Schl. F.sp. vasinfectum (Atk.) Snyd. & Hans.
45.2 50.2 49.1 62.9 56.2 71.0 48.7 69.6 53.1 45.5 65.9 60.3 67.9 41.3 33.3 15.3 10.4 19.1 17.1 20.5 11.5 19.5 10.9
72.6 55.7 67.2 81.7 51.7 82.4 43.6 73.1 59.6 60.4 57.2 52.2 60.2 51.2 61.2 35.4 30.1 47.8 23.1 50.7 21.5 37.8 27.8
70.1 50.4 65.1 85.6 65.8 89.0 52.7 68.1 46.8 68.5 67.3 64.1 67.9 46.7 58.7 34.1 29.3 40.2 25.6 57.6 23.4 35.4 27.1
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Table 2. Cont. Inhibition Ratio (%) Compd.
P. S. CapasiciLeonian sclerotiorum
4-c 4-d 4-e 4-f 4-g 5-a 5-b 5-c 5-d 5-e 5-f 6-a 6-b 6-c 6-d 6-e 6-f Chlorothalonil
30.3 35.4 39.1 38.7 24.5 42.3 37.6 47.2 65.2 67.7 68.2 23.1 30.0 31.2 57.1 50.3 51.6 94.2
30.5 34.7 32.1 31.7 13.5 57.6 48.5 43.1 67.6 64.9 56.1 46.7 39.8 42.8 64.7 56.3 41.2 95.5
B. cinerea
Pyricularia oryzae Cav.
Fusarium oxysporum Schl. F.sp. vasinfectum (Atk.) Snyd. & Hans.
11.2 20.3 21.1 22.2 12.1 36.1 23.7 19.2 23.2 22.1 27.6 23.5 17.1 18.6 26.7 27.4 29.1 98.0
32.3 35.6 30.0 40.2 21.3 62.7 42.3 40.8 69.2 56.9 60.5 32.0 42.3 28.7 50.2 48.9 40.8 89.2
33.1 37.8 31.9 43.1 20.9 61.3 39.2 30.0 70.9 69.5 71.5 35.9 40.8 37.6 58.6 59.3 57.8 94.2
In general, the following structure-activity relationships (SAR) in compounds 1, 2, 3, 4, 5 and 6 were observed: (1) As a whole, series 1 and 2 exhibited good fungicidal activities against P. CapasiciLeonian, Sclerotinia sclerotiorum (Lib.) de Bary, Pyricularia oryzae Cav. and Fusarium oxysporum Schl. F.sp. vasinfectum (Atk.) Snyd. & Hans. than the other series. (2) For the series 1 and 2, the fungicidal activities were increased by improving the electron-withdrawing ability of substituents on the benzene ring such as compounds 1-d (R2 = 4-F-C6 H4 -), 1-e (R2 = 4-NO2 -C6 H4 -), 1-f (R2 = 4-Cl-C6 H4 -), 2-d (R2 = 4-F-C6 H4 -), 2-e (R2 = 4-NO2 -C6 H4 -) and 2-f (R2 = 4-Cl-C6 H4 -); When the substituent group (R2 ) were substituted phenyl, the fungicidal activities of series compounds were superior to that with substituent alkyl. (3) Compared series 1 and 2, on an overall level the former (R1 = Me) displayed a better fungicidal activities than the latter (R1 = Bn). (4) Series 3 and 4 were obtained by deisopropylidenation of the compounds 1 and 2, they had the better water-solubility, but the fungicidal activities of compounds 3 and 4 against five species were decreased obviously. (5) In order to improve the fat solubility, the compounds 5 and 6 were synthesized. The fungicidal activities of compounds 5 and 6 were better than compounds 3 and 4, but lower than compounds 1 and 2. 2.3. Bioassay of Enzyme Inhibitory Activities Inhibitory activities of all the synthesized compounds towards Candida albicans GlcN-6-P synthase were evaluated using the optimized Elson-Morgan method as previously reported [25]. The absorption value of the solution was measured at 585 nm, and then the concentration was counted by the specification curve which was determined thanks to the relation between the absorption value and the concentration of glucosamine-6-phosphate. The inhibition rates were given in Table 3 at 0.35 mm. Table 3. Enzyme inhibition Rate of Compounds 1, 2, 3, 4, 5 and 6 at 0.35 mm. Compd.
Inhibition Rate (%)
Compd.
Inhibition Rate (%)
Compd.
Inhibition Rate (%)
Compd.
Inhibition Rate (%)
1-a 1-b 1-c 1-d 1-e 1-f 1-g 2-a 2-b 2-c
15.2 16.1 11.6 17.5 16.0 26.3 10.3 11.1 14.9 12.4
2-d 2-e 2-f 2-g 3-a 3-b 3-c 3-d 3-e 3-f
15.5 18.3 12.8 17.8 35.8 27.4 28.1 33.6 37.9 44.1
3-g 4-a 4-b 4-c 4-d 4-e 4-f 4-g 5-a 5-b
31.1 26.1 30.5 19.4 27.9 21.4 28.7 29.6 25.7 23.2
5-c 5-d 5-e 5-f 6-a 6-b 6-c 6-d 6-e 6-f
29.7 27.9 24.0 30.3 11.2 21.1 19.4 23.5 25.3 20.1
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As was shown, most of the tested compounds exhibited some enzyme inhibitory activities against glucosamine-6-phosphate synthase at 0.35 mm. On the whole, Although Series 1 and 2 displayed a better fungicidal activities against five species, they exhibited poor enzyme inhibitory activities. Series 3 and 4 without the OH-protection at both 1- and 2-position exhibited better enzyme inhibitory activities than the other series. By and large, the enzyme inhibitory activities of Series 5 and 6 with the OH-acetylation at 1 and 2-position were better than Series 1 and 2 but lower than Series 3 and 4. Compounds 3-a, 3-d, 3-e and 3-f were more active against glucosamine-6-phosphate synthase than the other compounds. 3. Experimental Section 3.1. General Methods All starting materials and reagents purchased from Sigma-Aldrich (Beijing, China) and Sinopharm Chemical Reagent Beijing Co., Ltd. (Beijing, China). Solvents were purified in the usual way. All reactions were carried out under a nitrogen atmosphere if necessary. All reactions were monitored by thin-layer chromatography (TLC) (the Silica gel thin plate purchased from Yantai Dexin Biological Technology Co., Ltd., Yantai, China) analysis and TLC was performed on silica gel HF with detection by charring with 30% (v/v) H2 SO4 in CH3 OH or by UV detection (254 nm). Column chromatography was conducted by elution of a column (8 × 100, 16 × 240, 18 × 300, 35 × 400 mm) of silica gel (200–300 mesh) with EtOAc–PE (b. p. 60–90 ◦ C) as the eluent. Optical rotations were recorded using a Perkin-Elmer 241 polarimeter (Perkin-Elmer, Waltham, MA, USA). 1 H-NMR (400 MHz) and 13 C-NMR (100 MHz) spectra was recorded in CDCl3 , Meth-d4 or DMSO-d6 with a Bruker DPX400 spectrometer (Brook (Beijing) science and Technology Co., Ltd., Beijing, China), using Tetramethyl silane (TMS) as internal standard; Mass spectra were obtained with Agilent 1100 series LC/MSD mass spectrometer (Agilent Technologies Inc., Beijing, China). High-resolution mass spectra (HRMS) were performed by the Peking University. Melting points were measured on a Yanagimoto melting-point apparatus (Yanagimoto MFG CO, Kyoto, Japan) and are uncorrected. Solutions were concentrated at a temperature
