Jun'ichi Nagasawa

Synthesis of C-glycosyl compounds by the addition of glycosyl radicals to olefins☆

The Bu3SnH - AIBN induced radical additions of 2,3,4,6-tetra-O-acetyl-D-glucopyranosyl derivatives, bearing α-Br (1), α-I (5) β-OCSSMe (7), and β-SePh (8) groups on the anomeric carbon, with olefins such as dimethyl maleate, methyl vinyl ketone, dimethyl acetylenedicarboxylate, butyl vinyl ether, and N-ethylmaleimide were examined for a synthesis of C-glycosyl compounds.

Highly stereoselective C-α-d-ribofuranosylation. Reactions of d-ribofuranosyl fluoride derivatives with enol trimethylsilyl ethers and with allyltrimethylsilane

Abstract 2,3,5-Tri-O-methyl- d -ribofuranosyl flouride (6), 2,3-di-O-benzyl-5-O-methyl- d -ribofuranosyl fluoride (7), and 5-O-benzyl-2,3-di-O-methyl- d -ribofuranosyl fluoride (8) were obtained in 57 (6α, 15; and 6β, 42), 87 (7α, 22; and 7β, 65), and 85.5 (8α, 35.5; and 8β, 50%) yields, respectively, from the corresponding OH-1 derivatives by the reaction with N,N-diethyl-1,1,2,3,3,3-hexafluoropropylamine, adduct of hexafluoropropene with diethylamine. These fluorides and 2,3,5-tri-O-benzyl- d -ribofuranosyl fluoride (5) reacted with isopropenyl trimethylsilyl ether, (Z)-1-ethyl-1-propenyl trimethylsilyl ether, and allyltrimethylsilane, in the presence of boron trifluoride·diethyl etherate to give the corresponding 1- d -ribofuranosyl-2-propanones, 2- d -ribofuranosyl-3-pentanones, and 3- d -ribofuranosyl-1-propenes in good yields. C-Acetonylation was confirmed to afford the α- d anomer as the initial product, and the α- d anomer was isomerized into the corresponding β- d anomer to give a mixture. The C-allylation reaction gave only the α- d anomer. C-Pentanonylation, however, gave a mixture of diastereoisomers that could not be isolated. All reactions afforded almost the same results starting with either α- or β- d -ribofuranosyl fluoride. No reaction of the β anomer of 5 with 1-isopropyl-2-methyl-1-propenyl trimethylsilyl ether took place.

Additions of a ribofuranosyl radical to olefins. A formal synthesis of showdomycin

Abstract The Bu3SnH - AIBN induced radical additions of 5- 0 -benzoyl-2,3- 0 -isopropylidene-1- 0 -methylthiothiocarbonyl-β-D-ribofuranose (1) to olefins such as dimethyl maleate, methyl vinyl ketone, methyl acrylate etc. gave corresponding C-ribofuranosyl compounds. And one of the adducts was converted to the key intermediate of a showdomycin synthesis.

Structural elucidation and a novel reductive cleavage of ribofuranosyl ring C-1 - O bond of the intramolecular C-arylation product of tri-O-benzyl-β-D-ribofuranosyl fluoride

Abstract Treatment of 2,3,5-tri- O -benzyl-β- D -ribofuranosyl fluoride ( 1 ) with BF 3 ·OEt 2 in CH 2 Cl 2 gave the intramolecular C -arylation product ( 2 ) formed from the reaction with the 2- O -benzyl group in a 83% yield. Catalytic transfer hydrogenolysis of 2 using HCOOH as a hydrogen donor and the following acetylation of the product gave (3 S ,1′ S ,2′ R )-3-(1,2,3-triacetoxypropyl)isochroman ( 9 ) in a 68% total yield.

Synthetic studies of carbohydrate derivatives by photochemical reactions. Part 16. Synthesis of DL-apiose derivatives by photochemical cycloaddition of 1,3-dihydroxypropan-2-one derivatives with ethenediol or ethenol derivatives

Irradiation of a benzene solution of 1,3-diacetoxypropan-2-one (5) and 1,3-dioxol-2-one (6) with a high-pressure mercury lamp gave a photocycloaddition product, (7-acetoxymethyl-3-oxo-2,4,6-trioxabicyclo[3.2.0]heptan-7-yl)-methyl acetate (7)(55% yield). Similar photocycloadditions of (5) with (Z)-vinylene diacetate (23), with (Z)-2-(benzyloxy)vinyl acetate (25), with 2,3-dihydro-1,4-dioxin (27), with vinyl acetate (28), with isopropenyl acetate (29), with ethoxyethene (30), and with 1,1-diethoxyethene (43) afforded cis-4,4-bis(acetoxymethyl)oxetan-2,3-diyl diacetate (31)(46% yield) and the trans-isomer (32)(49% yield); 2,2-bis(acetoxymethyl)-4-(benzyloxy)-oxetan-3-yl acetate (33)(composed of the two isomers; 11% and 26% yields) and 4,4-bis-(acetoxymethyl)-3-(benzyloxy)oxetan-2-yl acetate (38)(composed of the two isomers; 11% and 9% yields); (8-acetoxymethyl-2,5,7-trioxabicyclo[4.2.0]oct-8-yl)methyl acetate (34)(25% yield); 2,2-bis(acetoxymethyl)oxetan-3-yl acetate (35)(28% yield) and 4,4-bis(acetoxymethyl)oxetan-2-yl acetate (39)(15% yield); 2,2-bis(acetoxymethyl)-3-methyloxetan-3-yl acetate (36)(55% yield); (2-acetoxymethyl-3-ethoxyoxetan-2-yl)methyl acetate (37)(53% yield); and (2-acetoxymethyl-3,3-diethoxyoxetan-2-yl)methyl acetate (44)(48% yield) and ethyl 4-acetoxy-3-acetoxymethyl-3-hydroxybutyrate (45)(19% yield), respectively. The reaction of (5) with (43) was also induced thermally to give ethyl 4-acetoxy-3-(acetoxymethyl)coronate (46)(24% yield) in addition to (45)(20% yield). Photocycloaddition of diethyl mesoxalate (21) with (6) gave diethyl 3-oxo-2,4,6-trioxabicyclo[3.2.0]heptane-7,7-dicarboxylate (22)(23% yield). On the other hand, the reactions of 1,3-dimethoxy-(8) and 1,3-bis(benzyloxy)-propan-2-one (13) respectively with (6) afforded none of the expected photocycloadducts, but several products due to the intramolecular hydrogen abstraction from (8) and (13). The reaction of 2,2-dimethyl-1,3-dioxan-5-one (2) with (6) was also accompanied by predominant decomposition of (20).