Nitrous acid deamination of conformationally inverted aminodeoxyhexopyranoses

Nitrous acid deamination of 2-amino-1,6-anhydro-2-deoxy-β-D-glucopyranose (1) in the presence of weakly acidic, cation-exchange resin gave 1,6:2,3-dianhydro-β-D-mannopyranose (3) and 2,6-anhydro-D-mannose (6), characterized, respectively, as the 4-acetate of 3 and the per-O-acetylated reduction product of 6, namely 2,3,4,6- tetra-O-acetyl-1,5-anhydro-D-mannitol, obtained in the ratio of 7:13. Comparative deaminatior of the 4-O-benzyl derivative of 1 led to similar qualitative results. Deamination of 3-amino-1,6-anhydro-3-deoxy-β-D-glucopyranose gave 1,6:2,3- and 1,6:3,4-dianhydro-β-D-allopyranose (13 and 16), characterized as the corresponding acetates, obtained in the ratio of 31:69, as well as the corresponding p-toluenesulfonates. Deamination of 4-amino-1,6-anhydro-4-deoxy-β-D-glucopyranose and of its 2-O-benzyl derivative gave the corresponding 1,6:3,4-D-galacto dianhydrides as the only detectable products. 2,5-Anhydro-D-glucose, characterized as the 1,3,4,6-tetra-O- acetyl derivative of the corresponding anhydropolyol, was obtained in 39% yield from the same deamination reaction performed on 2-amino-1,6-anhydro-2-deoxy-β-D- mannopyranose (24). In 90% acetic acid, the nitrous acid deamination of 24, followed by per-O-acetylation, gave only 1,3-4-tri-O-acetyl-2,5-anhydro-α-D-glucoseptanose. In the case of 1,6-anhydro-3,4-dideoxy-3,4-epimino-β-D-altropyranose, only the corresponding glycosene was formed, namely, 1,6-anhydro-3,4-dideoxy-β-D-threo--hex-3-enopyranose.     

Chemical modification of the nonreducing,terminal group of maltotriose

O-α-d-Galactopyranosyl-(1→4)-O-α-d-glucopyranosyl-(1→4)-d-glucopyranose (12) was prepared by inversion of configuration at C-4″ of 2,3,2′,3′,6′,2″,3″-hepta-O-acetyl-1,6-anhydro-4″,6″-di-O-methylsulfonyl-β-maltotriose (7), followed by O-deacylation, acetylation, acetolysis, and de-O-acetylation. The intermediate 7 was obtained by treatment of 1,6-anhydro-β-maltotriose (2) with benzal chloride in pyridine, followed by acetylation, removal of the benzylidene group, and methane-sulfonylation. Selective tritylation of 2 and subsequent acetylation afforded 2,3,2′,3′,6′,2″,3″,4″-octa-O-acetyl-1,6-anhydro-6″-O-trityl-β-maltotriose (6), which was O-detritylated and p-toluenesulfonylated to give 2,3,2′,3′,6′,2″,3″,4″-octa-O-acetyl-1,6-anhydro-6″-O-p-tolylsulfonyl-β-maltotriose (13). Nucleophilic displacement of 13 with thioacetate, iodide, bromide, chloride, and azide ions gave 6″-S-acetyl- (14), 6″-iodo- (15), 6″-bromo- (16), 6″-chloro- (19), and 6″-azido- (20) 1,6-anhydro-β-maltotriose octaacetates, respectively. 6″Deoxy- (18) and 6″-acetamido-6″-deoxy (21) derivatives of 1,6-anhydro-β-maltotriose decaacetates were also prepared from 15 and 16, and 20, respectively. Acetolysis of 14, 15, 16, 18, 19, and 21 afforded 1,2,3,6,2′,3′,6′,2″,3″,4″-deca-O-acetyl-6″-S-acetyl (22), -6″-iodo (23), -6″-bromo (24), -6″-deoxy (25), -6″-chloro (26), and -6″-acetamido-6′-deoxy (27) derivatives of α-maltotriose, respectively. O-Deacetylation of 24, 25, and 26 furnished 6″-bromo-(28), 6″-deoxy- (29), and 6″-chloro- (30) maltotrioses, respectively, which on acetylation gave the corresponding β-decaacetates.     

Chemical Syntheses of 4-O-α and -β-D-galactopyranosyl-D-galactose and 3-O-α- and -β-D-galactopyranosyl-D-galactose

Reaction of 2,3-di-O-acetyl-1,6-anhydro-β-D-galactopyranose (2) with 2,3,4,6-tetra- O-acetyl-α-D-galactopyranosyl bromide in the presence of mercuric cyanide and subsequent acetolysis gave 1,2,3,6-tetra-O-acetyl-4-O-(2,3,4,6-tetra-O-acetyl-α-D-galactopyranosyl)-α-D-galactopyranose (4, 40%) and 1,2,3,6-tetra-O-acetyl-4-O-(2,3,4,6-tetra-O-acetyl-β-D-galactopyranosyl)-α-D-galactopyranose (5, 30%). Similarly, reaction of 2,4-di-O-acetyl-1,6-anhydro-β-D-galactopyranose (3) gave 1,2,4,6-tetra-O-acetyl-3-O-(2,3,4,6-tetra-O-acetyl-α-D-galactopyranosyl)-α-D-galactopyranose (6, 46%) and 1,2,4,6-tetra-O-acetyl-3-O-(2,3,4,6-tetra-O-acetyl-β-D-galactopyranosyl)-α-D-galactopyranose (7, 14%). The anomeric configurations of 4-7 were assigned by n.m.r. spectroscopy. Deacetylation of 4-7 afforded 4-O-α-D-galactopyranosyl-D-galactose (8), 4-O-β-D-galactopyranosyl-D-galactose (9), 3-O-α-D-galactopyranosyl-D-galactose (10), and 3-O-β-D-galactopyranosyl-D-galactose (11), respectively.     

Studies related to the synthesis of derivatives of 2,6-diamino-2,3,4,6-tetradeoxy-D-erythro-hexose (purpurosamine C), a component of gentamicin C12

Reduction of 1,6-anhydro-3,4-dideoxy-β-D-glycero-hex-3-enopyranos-2-ulose (levoglucosenone) with lithium aluminium hydride afforded principally 1,6-anhydro-3,4-dideoxy-β-D-threo-hex-3-enopyranose (3), which was converted into 3,4-dihydro-2(S)-hydroxymethyl-2H-pyran (8) following acid-catalysed methanolysis and reductive rearrangement of the resulting α-glycoside 4 with lithium aluminium hydride. 1,6-Anhydro-3,4-dideoxy-2-O-toluene-p-sulphonyl-β-D-threo-hexopyranose, prepared from 3, reacted slowly with sodium azide in hot dimethyl sulphoxide to give 1,6-anhydro-2-azido-2,3,4-trideoxy-β-D-erythro-hexopyranose, which was transformed into a mixture of methyl 2-acetamido-6-O-acetyl-2,3,4-trideoxy-α-D-erythro-hexopyranoside (10) and the corresponding β anomer following acid-catalysed methanolysis, catalytic reduction, and acetylation. Acid treatment of methyl 4,6-O-benzylidene-3-deoxy-α-D-erythro-hexopyranosid-2-ulose yielded the enone 15, which was readily transformed into methyl 6-O-acetyl-3,4-dideoxy-α-D-glycero-hexopyranosid-2-ulose (19). Procedures for the conversions of DL-8, 10, and 19 into methyl 2,6-diacetamido-2,3,4,6-tetradeoxy-α-D-erythro-hexopyranoside (methyl N,N′-di-acetyl-α-purpurosaminide C) have already been described.     

Ring-opening reactions of sucrose epoxides: Synthesis of 4′-derivatives of sucrose

The 2,1′-O-isopropylidene derivative (1) of 3-O-acetyl-4,6-O-isopropylidene-α-d-glucopyranosyl 6-O-acetyl-3,4-anhydro-β-d-lyxo-hexulofuranoside and 2,3,4-tri-O-acetyl-6-O-trityl-α-d-glucopyranosyl 3,4-anhydro-1,6-di-O-trityl-β-d-lyxo-hexulofuranoside have been synthesised and 1 has been converted into 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl 1,6-di-O-acetyl-3,4-anhydro-β-d-lyxo-hexulofuranoside (2). The S_N2 reactions of 2 with azide and chloride nucleophiles gave the corresponding 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl 1,3,6-tri-O-acetyl-4-azido-4-deoxy-β-d-fructofuranoside (6) and 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl 1,3,6-tri-O-acetyl-4-chloro-4-deoxy-β-d-fructofuranoside (8), respectively. The azide 6 was catalytically hydrogenated and the resulting amine was isolated as 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl 4-acetamido-1,3,6-tri-O-acetyl-4-deoxy-β-d-fructofuranoside. Treatment of 5 with hydrogen bromide in glacial acetic acid followed by conventional acetylation gave 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl 1,3,6-tri-O-acetyl-4-bromo-4-deoxy-β-d-fructofuranoside. Similar S_N2 reactions with 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl 1,6-di-O-acetyl-3,4-anhydro-β-d-ribo-hexulofuranoside (12) resulted in a number of 4′-derivatives of α-d-glucopyranosyl β-d-sorbofuranoside. The regiospecific nucleophilic substitution at position 4′ in 2 and 12 has been explained on the basis of steric and polar factors.     

Studies on dextranases. 3. Insolubilization of a bacterial dextranase

Ammonium hydroxide treatment of 1,6:2,3-dianhydro-4-O-benzyl-β-D-mannopyranose, followed by acetylation, gave 2-acetamido-3-O-acetyl-1,6-anhydro-4-O-benzyl-2-deoxy-β-D-glucopyranose which was catalytically reduced to give 2-acetamido-3-O-acetyl-1,6-anhydro-2-deoxy-β-D-glucopyranose (6), the starting material for the synthesis of (1→4)-linked disaccharides bearing a 2-acetamido-2-deoxy-D-glucopyranose reducing residue. Selective benzylation of 2-acetamido-1,6-anhydro-2-deoxy-β-D-glucopyranose gave a mixture of the 3,4-di-O-benzyl derivative and the two mono-O-benzyl derivatives, the 4-O-benzyl being preponderant. The latter derivative was acetylated, to give a compound identical with that just described. For the purpose of comparison, 2-acetamido-4-O-acetyl-1,6-anhydro-2-deoxy-β-D-glucopyranose has been prepared by selective acetylation of 2-acetamido-1,6-anhydro-2-deoxy-β-D-glucopyranose.Condensation between 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl bromide and 6 gave, after acetolysis of the anhydro ring, the peracetylated derivative (17) of 2-acetamido-2-deoxy-4-O-β-D-glucopyranosyl-α-D-glucopyranose. A condensation of 6 with 3,4,6-tri-O-acetyl-2-deoxy-2-diphenoxyphosphorylamino-α-D-glucopyranosyl bromide likewise gave, after catalytic hydrogenation, acetylation, and acetolysis, the peracylated derivative (21) of di-N-acetylchitobiose.     

Umlagerungsreaktionen bei der einwirkung von trifluormethansulfonsäure auf 2,3,4-tri-O-acetyl-1,6-anhydro-β-D-talopyranose-und 2,3,4-tri-O-acetyl-1,6-anhydro-β-D-glucopyranose

2,3,4-Tri-O-acetyl-1,6-anhydro-,β-D-talopyranose gave, in the presence of trifluoromethanesulfonic acid, the two talo ions 7 and 8, which are formed in approximately equal amounts. The hydrolytic ring-opening of the two ions proceeds stereoselectively. From 7 was formed 2,3-di-O-acetyl-1,6-anhydro-β-D-talopyranose and from 8 3,4-di-O-acetyl-1,6-anhydro-β-D-talopyranose, both having an axial, acetoxyl group. The talo ion 9 can undergo ring-contraction to the 1,6-anhydrotalofuranose ion 2. The doubly ring-contracted 1,5-anhydrotalofuranose ion 3, which can arise from 2 and 8, was also formed, and afforded the tri-O-acetyl derivatives of the furanose compounds 5 and 11. The mechanism of the ring-contraction reactions is discussed. 2,3,4-Tri-O-acetyl-1,6-anhydro-β-D-glucopyranose gave preferentially with trifluoromethanesulfonic acid and antimony pentachloride the manno ion 33, which rearranged for the most part into the altro ion 34. The equilibrium between the manno ion 33 and the altro ion 34 is approximately 1:3.     

Acid-catalyzed pyrolytic synthesis and decomposition of 1,4:3,6-dianhydro-α-d-glucopyranose

1,4:3,6-dianhydro-α-d-glucopyranose (1) was formed, together with 1,6-anhydro-3,4-dideoxy-β-d-glycero-hex-3-enopyranos-2-ulose (levoglycosenone, 2) and levoglucosan (4), on acid-catalyzed pyrolysis of d-glucose, amylopectin, and cellulose. Pyrolysis of 1 in the presence of acid provided significant quantities of 2, indicating that 1 can act as a pyrolytic precursor of 2. A pyrolysis product from cellulose previously considered to be 1,6-anhydro-3-deoxy-β-d-erythro-hex-3-enopyranose (12) was shown to be dianhydride 1.     

Synthesis of 2- (and 6-) -dithian-2-yluracil nucleosides and their conversion into nucleoside derivatives

Addition of 2,2′-anhydro-[1-(3-O-acetyl-5-O-trityl-β-D-arabinofuranosyl)uracil] (1) to excess 2-litho-1,3-dithiane (2)in oxolane at ?78° gave 2-(1,3-dithian-2-yl)-1-(5-O-trityl-β-D-arabinofuranosyl)-4(1H)pyrimidinone (3), O²,2′-anhydro-5,6-di-hydro-6-(S)-(1,3-dithian-2-yl)-5′-O-trityluridine (4), and 2-(1,4-dihydroxybutyl)-1,3-dithiane (5) in yields of 15, 30, and 10% respectively. The structure of 3 was proved by its hydrolysis in acid to give 2-(1,3-dithian-2-yl)-4-pyrimidinone (6) and arabinose, and by desulfurization with Raney nickel to yield the known 2-methyl-1-(5-O-trityl-β-D-arabinofuranosyl)-4(1H)-pyrimidinone (7). Detritylation of 3 without glycosidic cleavage could only be effected by prior acetylation to 1-(2,3-di-O-acetyl-5-O-trityl-β-D-arabinofuranosyl)-2-(1,3-dithian-2-yl)-4(1H)-pyrimidinone (8) which, after treatment with acetic acid at room temperature for 65 h followed by the action of sodium methoxide gave 2-(1,3-dithian-2-yl)-1-β-D-arabinofuranosyl-4(1H)-pyrimidinone (10) in 45% yield. Detritylation of 4 in boiling acetic acid gave 5,6-dihydro-6-(S)-(1,3-dithian-2-yl)-1-β-D-arabinofuranosyluracil (12) and 3-[(S)-1-(1,3-dithian-2-yl)]propionamido-(1,2-dideoxy-β-D-arabinofurano)-[1,2-d]-2-oxazolidinone (13) in 10 and 90% yields, respectively. When 12 was kept in water or methanol for 7 days, quantitative conversion into 13 occurred. Acid hydrolysis of 12 afforded arabinose and 5,6-di-hydro-6-(1,3-dithian-2-yl)uracil (14), which was desulfurized with Raney nickel to the known 5,6-dihydro-6-methyluracil (15). Treatment of 13 with trifluoroacetic anhydride-pyridine yielded 77% of the cyano derivative 17. Similar dehydration of 3-(R)-1-methylpropionamido-(1,2-dideoxy-β-D-arabinofurano)-[1,2-d]-2-oxalidinone (18), obtained by desulfurization of 13, gave 60% of the nitrile 19. Hydrogenation of 19 over platinum oxide in acetic anhydride gave the acetamide derivative 20 in 95% yield. Nitrobenzoylation of 13 gave 3-[(S)-1-(1,3-dithian-2-yl)]cyanomethyl-3,5-di-O-p-nitrobenzoyl-(1,2-dideoxy-β-D-arabinofurano)-[1,2-d]-2-oxazolidinone (22), which was converted in 37% yield by treatment with methyl iodide in dimethyl sulfoxide into the aldehyde 24, characterized as the semicarbazone 25. The purification of 5 and its characterization as 2-(1,4-di-O-p-nitrobenzoylbutyl)-1,3-dithiane (27) is described.     

Seven new triterpenoids from the aerial parts of Ilex cornuta and protective effects against H2O2-induced myocardial cell injury

Seven new triterpenoids (1–7), together with two known ones (8–9), were isolated from the aerial parts ofIlex cornuta. The leaves of I. cornuta are the major source of “Kudingcha”, a popular herbal tea consumed in China and other countries. The structures of compounds 1–7 were determined as 20-epi-urs-12,18-dien-28-oic acid 3β-O-α-l-arabinopyranoside (1), 20-epi-urs-12,18-dien-28-oic acid 2′-O-acetyl-3β-O-α-l-arabinopyranoside (2), 20-epi-urs-12,18-dien-28-oic acid 3β-O-β-d-glucuronopyranoside-6-O-methyl ester (3), 3β,23-dihydroxy-20-epi-urs-12,18-dien-28-oic acid (4), 23-hydroxy-20-epi-urs-12,18-dien-28-oic acid 3β-O-α-l-arabinopyranoside (5), 23-hydroxy-20-epi-urs-12,18-dien-28-oic acid 3β-O-β-d-glucuronic acid (6), 23-hydroxy-20-epi-urs-12,18-dien-28-oic acid 3β-O-β-d-glucuronopyranoside-6-O-methyl ester (7), on the basis of spectroscopic analyses (IR, ESI–MS, HR-ESI–MS, 1D and 2D NMR) and chemical reactions. Protective effects against H₂O₂-induced H9c2 cardiomyocyte injury were tested in vitro for compounds 1–9, and the data showed that compound 4 had significant cell-protective effect. Compounds 1-9 did not show significant DPPH radical scavenging activity.     

Isolation of 2,5-anhydro-1,3-O-isopropylidene-6-O-trityl-D-glucitol and conformations of its 4-O-substituted and deprotected,acylated derivatives

Acidic dehydration of D-mannitol (1) gave a mixture of anhydrides (2) that was isopropylidenated and subsequently tritylated. A single component crystallized from the resulting mixture and was shown to be the novel 2,5-anhydro-1,3-O-isopropylidene-6-O-trityl-D-glucitol (4) by chemical and physical analysis and by comparison of its deprotected, dibenzoylated derivative (10) with authentic 2,5-anhydro-1,6-di-O-benzoyl-D-glucitol. Acid hydrolysis of 4 afforded pure 2,5-anhydro-D-glucitol (9) in better yield than by the previously reported route. The 4-O-acetyl (5), 4-O-chloro-acetyl (6), 4-O-methyl (7), and 4-O-(methylsulfonyl) (8) derivatives of 4, the tetra-O-acetyl (11) derivative of 9, and the 3,4-di-O-acetyl (12) derivative of 10, have been prepared and spectrally characterized. Complete proton-n.m.r. analysis yields first-order coupling constants that indicate the E₁ (D) conformation for the tetrahydrofuran ring and the chair conformation for the 1,3-dioxane ring of 4-2-8. Obtainable coupling constants suggest that 11 and 12 exist in the ^oE and/or ^oT₁, conformations.     

Sucrochemistry : Part X. 1′,4,6′-tri-O-mesylsucrose penta-acetate: A comparison of the reactivity at the 4 and 1′ positions

The 1′,4,6′-trisulphonate 2, obtained by mesylation of sucrose 2,3,3′,4′,6-penta-acetate (1), undergoes nucleophilic substitution with sodium benzoate in hexamethylphosphoric triamide at positions 1′,4, and 6′ to give 1,6-di-O-benzoyl-β-D-fructofuranosyl 4-O-benzoyl-α-D-galactopyranoside penta-acetate (3), and selectively at positions 4 and 6′ to give 6-O-benzoyl-1-O-mesyl-β-D-fructofuranosyl 4-O-benzoyl-α-D-galactopyranoside penta-acetate (4). The products 3 and 4 were identified from their ¹H-n.m.r. spectra and by O-deacylation to give β-D-fructofuranosyl α-D-galactopyranoside (5) and its 1-methanesulphonate 6, respectively. Treatment of the trisulphonate 2 with sodium azide gave analogous products, namely, 1,6-diazido-1,6-dideoxy-β-D-fructofuranosyl 4-azido-4-deoxy-α-D-galactopyranoside penta-acetate (8) and 6-azido-6-deoxy-1-O-mesyl-β-D-fructofuranosyl 4-azido-4-deoxy-α-D-galactopyranoside penta-acetate (7).     

A short synthesis of 4-deoxy-4-fluoroglucosaminides: Methylumbelliferyl N-acetyl-4-deoxy-4-fluoro-β-D-glucosaminide

A convenient method of synthesis of 1,6-anhydro-4-deoxy-2-O-tosyl-4-fluoro-β-D-glucopyranose by fusion of 1,6;3,4-dianhydro-2-O-tosyl-β-D-galactopyranose with 2,4,6-trimethylpyridinium fluoride was found. By a successive action of ammonia, methyl trifluoroacetate, and acetic anhydride, the resulting compound was transformed into 1,6-anhydro-3-O-acetyl-2,4-dideoxy-2-trifluoroacetamido-4-fluoro-β-D-glucopyranose, which was converted into 3,6-di-O-acetyl-2,4-dideoxy-2-trifluoroacetamido-4-fluoro-αD-glucopyranosyl fluoride by the reaction with HF/Py. The resulting fluoride was further used as a glycosyl donor in the synthesis of methylumbelliferyl N-acetyl-4-deoxy-4-fluoro-β-D-glucosaminide.     

Two crystalline pentofuranosyl bromides: tri-O-(p-nitrobenzoyl)-β-D-ribofuranosyl bromide and tri-O-(p-nitrobenzoyl)-α,β-D-xylofuranosyl bromide

Methyl α,β-D-ribofuranoside was p-nitrobenzoylated to give methyl tri-O-(p-nitrobenzoyl)-β-D-ribofuranoside (2),and this was treated with HBr in acetic acid to give tri- O-(p-nitrobenzoyl)-β-D-ribofuranosyl bromide (3). Bromide 3 could be converted into 2,5-anhydro-3,4,6-tri-O-(p-nitrobenzoyl)-D-allononitrile (4) with Hg(CN)₂, or hydrolyzed to 2,3,5-tri-O-(p-nitrobenzoyl)-D-ribose (5). On p-nitro- benzoylation, 5 gave tetra-O-(p-nitrobenzoyl)-β-D-ribofuranose (6). The synthesis of tri-O-(p-nitrobenzoyl)-α-β-D-xylofuranosyl bromide (11) started with methyl 3,5-O-isopropylidene-β-D-xyldfuranoside (7), which was p-nitrobenzoylated to give ester 8; this was then hydrolyzed, and the product p-nitrobenzoylated to give methyl tri-O-(p-nitrobenzoyl)-β-D-xylofuranoside (10) which, on treatment with HBr in CH₂Cl₂, afforded the desired bromide (11). Nucleophilic replacement with Hg(CN)₂ afforded 2,5-anhydro-3,4,6-tri-O-(p-nitrobenzoyl)-D-gulononitrile (12).     

The synthesis of chlorodeoxyhexofuranoid derivatives

The reaction of 1,2-O-isopropylidene-α- d-glucofuranose with sulfuryl chloride at 0° and at 50° afforded 6-chloro-6-deoxy-1,2-O-isopropylidene-α- d-glucofuranose 3,5-bis(chlorosulfate) ( 3) and 5,6-dichloro-5,6-dideoxy-1,2-O-isopropylidene-β- l-idofuranose 3-chlorosulfate ( 7, not characterised), respectively. Dechlorosulfation of 3 afforded the hydroxy derivative, whereas treatment of 3 with pyridine gave the 3,5-(cyclic sulfate). Dechlorosulfation of 7 afforded 5,6-dichloro-5,6-dideoxy-1,2-O-isopropylidene-β- l-idofuranose which, on acid hydrolysis, was converted into 3,6-anhydro-5-chloro-5-deoxy- l-idofuranose. 5-Chloro-5-deoxy-α- l-idofuranosidurono-6,3-lactone and 5-chloro-5-deoxy-β- l-idofuranurono-6,3-lactone derivatives were also prepared.     

Thiophenes,polyacetylenes and terpenes from the aerial parts of Eclipata prostrata

One new bithiophenes, 5-(but-3-yne-1,2-diol)-5′-hydroxy-methyl-2,2′-bithiophene (2), two new polyacetylenic glucosides, 3-O-β-d-glucopyranosyloxy-1-hydroxy-4E,6E-tetradecene-8,10,12-triyne (8), (5E)-trideca-1,5-dien-7,9,11-triyne-3,4-diol-4-O-β-d-glucopyranoside (9), six new terpenoid glycosides, rel-(1S,2S,3S,4R,6R)-1,6-epoxy-menthane-2,3-diol-3-O-β-d-glucopyranoside (10), rel-(1S,2S,3S,4R,6R)-3-O-(6-O-caffeoyl-β-d-glucopyranosyl)-1,6-epoxy menthane-2,3-diol (11), (2E,6E)-2,6,10-trimethyl-2,6,11-dodecatriene-1,10-diol-1-O-β-d-glucopyranoside (12), 3β,16β,29-trihydroxy oleanane-12-ene-3-O-β-d-glucopyranoside (13), 3,28-di-O-β-d-glucopyranosyl-3β,16β-dihydroxy oleanane-12-ene-28-oleanlic acid (14), 3-O-β-d-glucopyranosyl-(1→2)-β-d-glucopyranosyl oleanlic-18-ene acid-28-O-β-d-glucopyranoside (15), along with fifteen known compounds (1, 3–7, and 16–24), were isolated from the aerial parts of Eclipta prostrata. Their structures were established by analysis of the spectroscopic data. The isolated compounds 1–9 were tested for activities against dipeptidyl peptidase IV (DPP-IV), compound 7 showed significant antihyperglycemic activities by inhibitory effects on DPP-IV in human plasma in vitro, with IC₅₀ value of 0.51 μM. Compounds 10–24 were tested in vitro against NF-κB-luc 293 cell line induced by LPS. Compounds 12, 15, 16, 19, 21, and 23 exhibited moderate anti-inflammatory activities.     

Iridoids from Gentiana loureirii

Iridoid glycosides, 2′,3′,6′-tri-O-acetyl-4′-O-trans-p-(O-β-d-glucopyranosyl)coumaroyl-7-ketologanin (1), 2′-O-caffeoylloganic acid (2), 2′-O-p-hydroxybenzoylloganic acid (3), 2′-O-trans-p-coumaroylloganic acid (4), and 2′-O-cis-p-coumaroylloganic acid (5), were isolated from whole plants of Gentiana loureirii along with six known iridoids, 7-ketologanin (6), loganin (7), loganic acid (8), sweroside, boonein, and isoboonein, and three other known compounds. Their structures were elucidated by spectroscopic means and chemical correlations. The isolated iridoids were evaluated for antibacterial and antioxidant activities, but were either inactive or very weakly active.     

Pyrimidine homonucleoside analogues from 2,5-anhydroaldose derivatives

3,4-Di-O-acetyl-2,5-anhydro-D-xylose diisobutyl dithioacetal (1) reacts with bromine to give a monobromo derivative which, on condensation with 2,4-diethoxy-pyrimidine or its 5-methyl analogue, affords the protected nucleoside derivatives 4 and 11, respectively; ammonolysis of 4 gave the cytosine “homonucleoside” 7, and hydrolysis of 11 gave the thymine “homonucleoside” 12. The same type of “homonucleoside” may be produced by cyclization of the sugar chain in a suitable acyclic-sugar nucleoside, as in the conversion of 1-S-ethyl-1-thio-1-(uracil-1-yl)-D-xylitol (16, obtained from tetra-O-acetyl-D-xylose diethyl dithioacetal, 9), by the action of one molar equivalent of p-toluenesulfonyl chloride, into a homonucleoside isolated as its diacetate 17; acyclic-sugar derivatives not susceptible to such cyclization afford instead the 5-p-toluenesulfonates, as exemplified by the conversion of the D-arabino analogue (13) of 16 into the 5′-ester 14. When cyclohexene is used to remove the excess of bromine in the preparation of nucleoside analogues from dithioacetals, the alkylsulfenyl bromide produced may react, by way of its cyclohexene adduct, with the hoterocyclic base to give cyclohexane-base adducts, for example, compounds 6 and 10.     

Hydrogenolysis of benzylidene acetals of 1,6-anhydro-β-d-galactopyranose derivatives with the LiAlH4—AlCl3 reagent

Benzylidenation of 1,6-anhydro-β-d-galactopyranose (1) and its 2-O-acetyl (2) and 2-O-allyl (3) derivatives under various conditions afforded mixtures of 1,6-anhydro-exo- and -endo-3,4-O-benzylidene-β-d-galactopyranose (4 and 5) and the2-O-acetyl (6 and 7) and 2-O-allyl (8 and 9) derivatives, respectively. Hydrogenolysis of the exo (4 and 8) or the endo (5 and 9) derivatives with the LiAlH₂—AlCl₃ reagent gave only the 3-O-benzyl derivatives (10 and 11).     

Accès à des sulfures d'alkyle et de furannyle à partir de dithio-acétals de pentoses

Sodium iodide—zinc in N,N-dimethylformamide at 150° converted 2,5-anhydro-3,4-di-O-p-tolylsulfonyl-D-xylose diisobutyl dithioacetal into a mixture of three substituted furans, namely 2-[(isobutylthio)methyl]furan (2), and its 3-isobutylthio- (3), and 4-isobutylthio- (5) derivatives. The relative proportions of 2, 3, and 5, determined by g.l.c.—mass spectrometry, varied according to the relative proportions of reactants employed. A similar type of transposition—elimination is also encountered in the absence of sodium iodide. Compound 3 is also produced from D-xylose disobutyl dithioacetal by extended treatment with 2-methylpropanethiol—hydrochloric acid. The furan derivatives 3 and 5 were characterized mainly by n.m.r.—spectral studies on their Diels—Alder adducts with maleic anhydride, and the mechanism of their formation is discussed. 2,5-Anhydro-3,4-di-O-p-tolylsulfonyl-D-xylose ethylene dithioacetal (13), its ribo epimer (15), and its L-arabino diisobutyl dithioacetal analog (20) all reacted with sodium iodide—zinc in N,N-dimethylformamide exclusively by an E2 type of elimination with formation of the anticipated 3-alkenes, namely 2,5-anhydro-3,4-dideoxy-D-glycero-pent-3-enose ethylene dithioacetal (14) and its diisobutyl dithioacetal analog.