Stereoselective reduction of 2-azido-1-phenylethanone derivatives by whole cells of marine-derived fungi applied to synthesis of enantioenriched β-hydroxy-1,2,3-triazoles

Several marine-derived fungi were evaluated by the bioreduction of 2-azido-1-phenylethanone 1, and the strains A. sydowii CBMAI 935 and M. racemosus CBMAI 847 were selected for the reduction of 2-azido-1-phenylethanone derivatives 2–4. Whole cells of A. sydowii CBMAI 935 promoted the reduction of 2-azido-1-phenylethanones 1–4 with high selectivities to yield the (S)-2-azido-1-phenylethanols 1a–4a. Bioreduction of compounds 1–4 by M. racemosus CBMAI 847 led to (R)-2-azido-1-phenylethanols for 1, 2 and 4 and (S)-2-azido-1-phenylethanol 3. Enantiomerically enriched 2-azido-1-phenylethanols 1a–4a and phenylacetylene 5 were applied in the synthesis of β-hydroxy-1,2,3-triazoles using CuSO₄ and sodium ascorbate leading to regioselective formation of enantioenriched 1,4-disubstituted 1,2,3-triazole compounds 1b–4b.     

Biotransformation of arenobufagin and cinobufotalin by Alternaria alternata

Abstract

The biotransformation of arenobufagin (1) and cinobufotalin (2), isolated from the natural medicine Chan Su, by Alternaria alternata AS 3.4578 was carried out. Incubation of 1 and 2 afforded six metabolites: 3-oxo-arenobufagin (1a), ψ-bufarenogin (1b), 3-oxo-ψ-bufarenogin (1c), 3-oxo-Δ⁴-derivative of cinobufotalin (2a), 3-oxo-cinobufotalin (2b) and 12β-hydroxycinobufotalin (2c). Among them, metabolites 1a, 1c and 2c are new compounds and their structures were characterized on the basis of their spectroscopic data (NMR, MS and IR). Compounds 1, 2, 1b, 2a and 2b were evaluated for their cytotoxicity against HepG2 and MCF-7 human cancer cells, and all of them showed significant inhibitory activities.     

柯拉斯那沉香的生物活性成分研究

为了解柯拉斯那(Aquilaria crassna)的化学成分,从其所产沉香中分离得到10个化合物,经波谱分析分别鉴定为:6,8-羟基-2-(2-苯乙基)色酮(1),6,8-二羟基-2-[2-(4-甲氧基苯)乙基]色酮(2),rel-(1a R,2R,3R,7b S)-1a,2,3,7b-tetrahydro-2,3-dihydroxy-5-(2-phenylethyl)-7H-oxireno[f][1]benzopyran-7-one(3),rel-(1a R,2R,3R,7b S)-1a,2,3,7b-tetrahydro-2,3-dihydroxy-[2-(4-methoxyphenyl)-ethyl]-7H-oxireno[f][1]benzopyran-7-one(4),rel-(1a R,2R,3R,7b S)-1a,2,3,7b-tetrahydro-2,3-dihydroxy-5-[2-(3-hydroxy-4-methoxyphenyl)-ethyl]-7H-oxireno[f][1]benzopyran-7-one(5),oxidoagarochromone B(6),oxidoagarochromone C(7),(5S,6R,7S,8R)-2-[2-(3′-hydroxy-4′-methoxyphenyl)ethyl]-5,6,7,8-tetrahydroxy-5,6,7,8-tetrahydrochromone(8),6,7-cis-dihydroxy-2-(2-phenylethyl)-5,6,7,8-tetrahydrochromone(9),N-trans-feruloyltyramine(10)。化合物3~5和8~10为首次从柯拉斯那沉香中分离得到。化合物1,3,6,7,9和10对乙酰胆碱酯酶具有一定的抑制活性,化合物4对人慢性髓原白血病细胞株K-562和人胃癌细胞株SGC-7901均具有较小的抑制作用,化合物1和3对人肝癌细胞株BEL-7402也有抑制活性。     

Homo-C-Nucleoside Analogs† II. Synthesis and Anomeric Configuration of 4-(2,5-Anhydro-D-Gluco-PEntitol-1-YL)-2-Phenyl2H-1,2,3-Triazole††

Abstract

Treatment of 4-(D-gluco-pentitol-l-y1)-2-pheny1–2H-1,2,3-triazole (1) with p-toluenesulfonyl chloride in pyridine solution, afforded the homo-C-nucleoside analog, 4-(2,5-anhydro-D-gluco-pentitol-1-yl)-2-phenyl-2H-1,2,3-triazole (2) as well as its partial p-toluenesulfonyl derivative (3). 4-(5-Chloro-5-deoxy-D-gluco-pentitol-1-yl)-2-phenyl-2H-1,2,3-triazole (8), was isolated as a byproduct from the reaction. The structure and anomeric configuration of 2 was determined by acylation, ¹H, ¹³C NMR, and NOE, spectroscopy as well as mass spectrometry.

     

Synthesis of trans-4-Amino-1-hydroxy-2-methyl-2-butene from Isoprene

A novel synthetic pathway to trans-4-amino-1-hydroxy-2-methyl-2-butene (7), a useful synthetic intermediate of zeatin, is presented here. On selective monophthalimide formation, the trans-1, 4-dibromo-2-methyl-2-butene (10) prepared from isoprene (1) predominantly gives trans-1-bromo-2-methyl-4-phthalimido-2-butene (11). The compound (11) is converted to 7 via trans-1-acetoxy-2-methyl-4-phthalimido-2-butene (6). The overall yield of 7 from 1 is 33.6%. Base-catalyzed hydrolysis of 11 also gives 7 directly. Zeatin can be prepared by the condensation of 7 with 6-chloropurine.     

Enzymatic resolution of rac-1,1-dimethyl-1-sila-cyclohexan-2-ol by ester hydrolysis or transesterification using a crude lipase preparation of Candida cylindracea

Summary rac-2-Acetoxy-1,1-dimethyl-1-sila-cyclohexane (rac-2) was synthesized by esterification of rac-1,1-dimethyl-1-sila-cyclohexan-2-ol (rac-1) with acetic anhydride. Enantioselective hydrolysis of rac-2 in aqueous solution, catalysed by a crude lipase preparation of Candida cylindracea (EC 3.1.1.3), led to the formation of (S)-1 (95% ee). Enantioselective transesterification of rac-1 with triacetin in isooctane, catalysed by the same enzyme preparation, yielded (S)-2 (95% ee), which was separated by chromatography from non-reacted (R)-1 (96% ee). Recrystallization led to an improvement of the enantiomeric purity of (R)-1 and (S)-1 up to >98% ee. Thus the enantiomers of rac-1 were prepared (100 mg scale) with high enantiomeric purities by the use of two different types of enzyme-catalysed reaction.     

Synthesis of 2-Bromomethyl-3-Hydroxy-2-Hydroxymethyl-Propyl Pyrimidine and Theophylline Nucleosides Under Microwave Irradiation. Evaluation of Their Activity Against Hepatitis B Virus

Alkylation of 2-methylthiopyrimidin-4(1H)-one (1a) and its 5(6)-alkyl derivatives 1b–d as well as theophylline (7) with 2,2-bis(bromomethyl)-1,3-diacetoxypropane (2) under microwave irradia-tion gave the corresponding acyclonucleosides 1-[(3-acetoxy-2-acetoxymethyl-2-bromomethyl)prop-1-yl]-2-methyl-thio pyrmidin-4(1H)-ones 3a–d and 7-[(3-acetoxy-2-acetoxymethyl-2-bromomethyl)prop-1-yl]theophylline (8), which upon further irradiation gave the double-headed acyclonucleosides 1,1 ′-[(2,2-diacetoxymethyl)-1,3-propylidene]-bis[(2-(methylthio)-pyrimidin-4(1H)-ones] 4a–c, and 7,7 ′-[(2,2-diacetoxymethyl)-1,3-propylidene]-bis(theophylline) (9). The deacetylated derivatives were obtained by the action of sodium methoxide. The activity of deacetylated nucleosides against Hepatitis B virus was evaluated. Compound 5b showed moderate inhibition activity against HBV with mild cytotoxicity.     

Interaction of (2′ -5′) and (3′ -5′) Linked 2-Aminoadenylyl-3-aminoadenosines with Polyuridylic Acid

Abstract

2′-5′ and 3′-5′ linked 2-aminoadenylyl-2-aminoadenosines [(2′-5′)n²Apn²A (1) and (3′-5′)n²Apn²A (2)] were synthesized by condensation of 5′-O-monomethoxytrityl-N ² N ⁶-dibenzoyl-2-aminoadenosine and N ²,N ⁶,2′,3′-O-tetrabenzoyl-2-aminoadenosine 5′-phosphate using dicyclohexylcarbodiimide (DCC). The conformational properties of these dimers 1 and 2 were examined by UV, NMR and CD spectroscopy. The results reveal that the 2′-5′-isomer 1 takes a stacked conformation, which contains a larger base-base overlap and is more stable against thermal perturbation with respect to the 3′-5′-isomer 2. Interactions of 1 and 2 with polyuridylic acid (Poly (U)) were also examined by Tm, mixing curves, UV and CD spectra. Both the dinucleoside isomers 1 and 2 formed a complex of 1 : 2 stoichiometry with poly(U), which was much more stable than that of the corresponding ApA isomer     

Highly selective biotransformation of (+)-(1S)- and (−)-(1R)-camphorquinone by Aspergillus wentii

Abstract

To clarify the structures of biotransformation products and metabolic pathways, the biotransformation of monoterpenoids, (+)- and (?)-camphorquinone (1a and b), has been investigated using Aspergillus wentii as a biocatalyst. Compound 1a was converted to (?)-(2S)-exo-hydroxycamphor (2a), (?)-(2S)-endo-hydroxycamphor (3a), (?)-(3S)-exo-hydroxycamphor (4a), (?)-(3S)-endo-hydroxycamphor (5a), and (+)-camphoric acid (6a). Compound 1b was converted to (+)-(2R)-exo-hydroxycamphor (2b), (+)-(2R)-endo-hydroxycamphor (3b), (+)-(3R)-exo-hydroxycamphor (4b), (+)-(3R)-endo-hydroxycamphor (5b), and (?)-camphoric acid (6b). Compound 1a mainly produced 2a (65.0%) with stereoselectivity, whereas 1b afforded 3b (84.3%) with high stereoselectivity. These structures were confirmed by gas chromatography–mass spectrometry, infrared, ¹H nuclear magnetic resonance (NMR), and ¹³C NMR spectral data. The products illustrate the marked ability of A. wentii for enzymatic oxidation and ketone reduction.     

Synthesis and Biological Evaluation of 9-(f-2, c-3-Bishydroxymethyl-r-cyclopropylmethyl)-9H-adenine (A Lower Methylene Homolog of Carbocyclic Oxetanocin) and Related Compounds

Abstract

Adenine (7 and 16), thymine (9a and 18a), and 5-fluorouracil (9b and 18b) involving f-2, c-3-bishydroxymethyl-r-1-cyclopropylmethyl- and t-2 t-3-bishydroxymethyl-r-1-cyclopropylmethyl residues were synthesized, starting from trans-1, 4-dibenzyloxy-2-butene and its cis isomer, respectively. These compounds were evaluated for anti HSV-1 activity.     

Ribosylation of the Base Residue of Inosine Derivatives by Phase-Transfer Catalysis

Abstract

Reaction of 2′,3′,5′-O-silylated inosine derivative 1 with 2, 3-O-isopropylidene-5-O-tritylribosyl chloride (3) in a two-phase (CH₂Cl₂-aq. NaOH) system in the presence of Bu₄NBr gave three products, i. e., 6-O-α-, 6-O-β-, and N ¹-β-isomers of glycosides 4, 5a, and 5b. A similar PTC reaction of 1 with 2, 3, 5-tri-O-benzylribosyl bromide (9) gave four regio- and stereo-isomers involving the N¹-β-glycoside 10. Reaction of 1 with 2, 3, 5-tri-O-benzoylribosyl bromide (11) afforded three products involving the desired N¹-β-glycoside 12b, which could be deprotected to give N ¹-ribosylinosine (15b) as a useful intermediate for the synthesis of cIDPR.

     

Total Synthesis of ( + )-Methyl Phaseates

( ± )-Methyl phaseates were synthesized from ( ± )-4-(6′-acetoxymethyl-2 ′,6′-dimethyl-1′-cyclohexen-1′-y1)-but-3-en-2-one (20), which was prepared from a useful terpenoid building block, ( ± )-2-hydroxymethyl-2,6-dimethyl-1-cyclohexanone (11a and 11b). Photooxidation of the cyclohexadiene intermediate (22), followed by alkaline hydrolysis and methylation, gave four stereoisomers of ( ± )-methyl phaseates: (2Z,4E)-cis form (2), (2E,4E)-cis form (24), (2Z,4E)-trans form (25) and (2E,4E)-trans form (26).     

Studies ON Epimeric-D-asabino-and-D-ribo-tetritol-1-yl-2-phenyl-2 H-1,2,3-triazoles. Synthesis and Anomeric Configuration of 4-(α-and β-D-Erythrofuranosyl)-2-phenyl-2 H-1,2,3-Triazole C-Nucleoside Analogs

Abstract

Treatment of 4-(D-arabino-tetritol-1-yl)-2-phenyl-2 H-1,2,3-triazole (1) with one mole equivalent of tosyl chloride in pyridine solution, afforded the C-nucleoside analogs, 4-(α-D-erythrofuranosyl)-2-phenyl-2 H-1,2,3-triazole (2) in 25% yield, as well as the byproduct 4-(4-chloro-4-deoxy-D-arabino-tetritol-1-yl)-2-phenyl-2 H-1,2,3-triazole(3). Treatment of the epimeric 4-(D-ribo-tetritol-1-yl)-2-phenyl-2 H-1,2,3-triazole(8) with tosyl chloride in pyridine solution afforded the anomeric C-nucleoside analogs, 4-(β-D-erythrofuranosyl)-2-phenyl-2 H-1,2,3-triazole (9) in 23% yield. Similar treatment of 8 with trifluoromethanesulfonyl chloride in pyridine solution afforded 9. The structure and anomeric configuration of these compounds were determined by acylation, NMR, NOE, circular dichroism spectroscopy and mass spectrometry.     

BcMAF2 activates BcTEM1 and represses flowering in Pak-choi (Brassica rapa ssp. chinensis)

Key message

BcMAF2 plays a key role in flowering regulation by controlling BcTEM1, BcSOC1 and BCSPL15 in Pak-choi.

Abstract

Flowering is a key event in the life cycle of plants. Flowering time shows an extensive variation from different Pak-choi (Brassica rapa ssp. chinensis) cultivars. However, the regulation mechanism of flowering in Pak-choi remains rarely known. In this study, a systematic identification and functional analysis of a Pak-choi MADS Affecting Flowering (MAF) gene, BcMAF2, was carried out. BcMAF2 encoded a protein containing a conserved MADS-box domain, which was localized in the nucleus. QPCR analysis indicated that the expression of BcMAF2 was higher in the leaves and flowers. Overexpression of BcMAF2 in Arabidopsis showed that BcMAF2 repressed flowering, which was further confirmed by silencing endogenous BcMAF2 in Pak-choi. In addition, Tempranillo 1 (TEM1) expression was up-regulated and MAF2 expression was down-regulated in the BcMAF2-overexpressing Arabidopsis. The expression of BcMAF2 and BcTEM1 was down-regulated in BcMAF2-silencing Pak-choi plants. The yeast one-hybrid, dual luciferase and qPCR results revealed that BcMAF2 protein could directly bind to BcTEM1 promoter and activate its expression, which was not reported in Arabidopsis. Meanwhile, a self-inhibition was found in BcMAF2. Taken together, this work suggested that BcMAF2 could repress flowering by directly activating BcTEM1.

     

Synthesis of N-Arylinosines

Abstract

2′,3′,5′-Tri-O(tetrahydropyran-2-yl)inosine 1 was treated with iodobenzene or 2-bromopyridine in the presence of cuprous oxide in pyridines to give the N¹ -aryl derivatives 2a, b. Deprotection of the products afforded N¹ -arylinosines 3a, b.     

Triterpenoids from <i>Uncaria rhynchophylla</i> and Their PTP1B Inhibitory Activity

Uncaria rhynchophylla (Gouteng) is a famous traditional Chinese medicine used for psychiatric and hypotensive purposes in China. In this study, the ethyl acetate (EtOAc) part of U. rhynchophylla was revealed with protein tyrosine phosphatase 1B (PTP1B) inhibitory activity. Subsequent investigation on the EtOAc part yielded one new triterpenoid, 3β-formyloxy-6β,19α-dihydroxyurs-12-en-28-oic acid (1) and four known ones, 3β,6β,19α-trihydroxyurs-12-en-28-oic acid (2), 2-oxopomolic acid (3), 3β,19α-dihydroxy-6-oxo-olean-12-en-28-oic acid (4) and sumaresinolic acid (5). The structure of compound 1 was determined by extensive HRESIMS, IR, 1D and 2D NMR spectroscopic analyses. Two ursane-type triterpenoids (2 and 3) showed selective inhibition on PTP1B with IC₅₀ values of 48.2 and 178.7 μM. The enzyme kinetic study suggested that compounds 2 and 3 were mix-type inhibitors on PTP1B with K_i values of 15.6 and 132.5 μM. This investigation manifests the antidiabetic potency of U. rhynchophylla with triterpenoids as the active constituents.     

Synthesis and Biological Evaluation of 1,3-Oxathiolane 5-Azapyrimidine, 6-Azapyrimidine,and Fluorosubstituted 3-Deazapyrimidine Nucleosides

Abstract

(2R,5S)-5-Amino-2-[2-(hydroxymethyl)-1,3-oxathiolan-5-y1]-1,2,4-triazine-3(2H)-one (8) and (2R,5R)-5-amino-2-[2-(hydroxymethyl)-1,3-oxathiolan-5-y1]-1,2,4-triazine-3(2H)-one (9) have been synthesized via a multi-step procedure from 6-azauridine. (2R,5S)-4-Amino-1-[2-(hydroxymethyl)-1,3-oxathiolan-5-y1]-1,3,5-triazine-2(1H)-one (11) and (2R,5R)-4-amino-1-[2-(hydroxymethyl)-1,3-oxathiolan-5-y1]-1,3,5-triazine-2(1H)-one (12), and the fluorosubstituted 3-deazanucleosides (19–24) have been synthesized by the transglycosylation of (2R,5S)-1-{2-[[(tert-butyldiphenylsilyl) oxy]methyl]-1,3-oxathiolan-5-y1} cytosine (2) with silylated 5-azacytosine and the corresponding silylated fluorosubstituted 3-deazacytosines, respectively, in the presence of trimethylsilyl trifluoromethanesulfonate as the catalyst in anhydrous dichloroethane, followed by deprotection of the blocking groups. These compounds were tested in vitro for cytotoxicity against L1210, B₁₆F₁₀, and CCRF-CEM tumor cell lines and for antiviral activity against HIV-1 and HBV.     

Preparation of Optically Active 2-Aminobutanoic Acid via Optical Resolution by Replacing Crystallization

An attempt was made to use a simple procedure to obtain (R)- and (S)-2-aminobutanoic acids [(R)- and (S)-1] which are non-proteinogenic α-amino acids and are useful as chiral reagents in asymmetric syntheses. Compound (RS)-1 p-toluenesulfonate [(RS)-2], which is known to exist as a conglomerate, was optically resolved by replacing crystallization with (R)- and (S)-methionine p-toluenesulfonate [(R)- and (S)-3] as optically active co-solutes. When (S)-3 was employed as the co-solute, (R)-2 was preferentially crystallized from a supersaturated solution of (RS)-2 in 1-propanol, as was (S)-2 in the presence of (R)-3. (R)- and (S)-2 recrystallized from 1-propanol were treated with triethylamine in methanol to give (R)- and (S)-1 in optically pure forms.     

Synthesis and Antimicrobial Activity of Chiral cis-Cycloheximide Isomers

Such (+)- and (?)-cis-cycloheximide isomers as isocyclohcximide (1a, 1b), α-epiisocycloheximide (2a, 2b) and neocycloheximide (3a, 3b) were synthesized by aldol condensation of (?)-(2R, 4R)- and (+)-(2S, 4S)-cis-2,4-dimethyl-1-cyclohexanone (5a, 5b). obtained by microbial resolution, with 4-(2-oxoethyl)-2,6-piperidinedione (7). The absolute configuration of the (?)-cis-ketone 5a was confirmed by chemical correlation with natural (2S, 4S, 6S, αR)-cycloheximide (4). The newly synthesized isomer, (?)-α-epiisocycloheximide (2b), showed strong antimicrobial activity against S. cerevisiae andP. oryzae close to that of natural cycloheximide (4).     

Synthesis and Structural Analysis of Oxadiazole Carboxamide Deoxyribonucleoside Analogs

Two novel C-linked oxadiazole carboxamide nucleosides 5-(2′-deoxy-3′,5′-β-D-erythro-pentofuranosyl)-1,2,4-oxadiazole-5-carboxamide (1) and 5-(2′-deoxy-3′,5′-β-D-erythro-pentofuranosyl)-1,2,4-oxadiazole-3-carboxamide (2) were successfully synthesized and characterized by X-ray crystallography. The crystallographic analysis shows that both unnatural nucleoside analogs 1 and 2 adapt the C2′-endo (“south”) conformation. The orientation of the oxadiazole carboxamide nucleobase moiety was determined as anti (conformer A) and high anti (conformer B) in the case of the nucleoside analog 1 whereas the syn conformation is adapted by the unnatural nucleoside 2. Furthermore, nucleoside analogs 1 and 2 were converted with high efficiency to corresponding nucleoside triphosphates through the combination chemo-enzymatic approach. Oxadiazole carboxamide deoxyribonucleoside analogs represent valuable tools to study DNA polymerase recognition, fidelity of nucleotide incorporation, and extension.