Gita Patel

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

Abstract 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 N 2 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 N 2 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.

Branched-chain sucroses: Synthesis and Wittig reaction of the 1′-aldehydo derivative of sucrose

Abstract The reaction of 2,3,4,3′,4′-penta- O -acetylsucrose ( 1 ) with 3.3 mol. equiv. of tert -butyldiphenylsilyl chloride in pyridine in the presence of 4-dimethylamino-pyridine gave the 6,1′,6′-tris( tert -butyldiphenylsilyl) derivative 2 (27%) and the 6,6′-bis( tert -butyldiphenylsilyl) derivative (67%). Oxidation of the HO-1′ in 3 with methyl sulphoxide and trifluoroacetic anhydride gave the 1′-aldehydo derivative 5 , which reacted with the stabilised Wittig reagent (Ph 3 PCHCO 2 Et) to give the 1′-ethoxycarbonylmethylene derivative 6 . Deacetylation of the hepta-acetate 7 of 6 with methanolic sodium methoxide was accompanied by a Michael addition reaction to give 2,1′-anhydro-1′-methoxycarbonylmethylsucrose.

Synthesis and ring-opening reactions of 4-chloro-4-deoxy-α-d-galactopyranosyl 3,4-anhydro-1,6-dichloro-1,6-dideoxy-β-d-lyxo-hexulofuranoside

Abstract Treatment of 4-chloro-4-deoxy-α- d -galactopyranosyl 1,6-dichloro-1,6-dideoxy-β- d -fructofuranoside ( 1 ) with 2.3 mol. equiv. of diethyl azodicarboxylate (DEAD) and 1.3 mol. equiv. of triphenylphosphine (TPP) in toluene gave a mixture of 3,6-anhydro-4-chloro-4-deoxy-α- d -galactopyranosyl 3,4-anhydro-1,6-dichloro-1,6-dideoxy-β- d - lyxo -hexulofuranoside ( 2 , 55%) and 4-chloro-4-deoxy-α- d -galactopyranosyl 3,4-anhydro-1,6-dichloro-1,6-dideoxy-β- d - lyxo -hexulofuranoside ( 3 , 35%). Compound 3 was also synthesised from 6- O - tert -butyldiphenylsilyl-4-chloro-4-deoxy-α- d -galactopyranosyl 1,6-dichloro-1,6-dideoxy-β- d -fructofuranoside by epoxidation with DEAD-TPP and removal of the silyl ether group with tetrabutylammonium fluoride. The S N 2 reactions of 2,3,6-tri- O -acetyl-4-chloro-4-deoxy-α- d -galactopyranosyl 3,4-anhydro-1,6-dichloro-1,6-dideoxy-β- d - lyxo -hexulofuranoside ( 5 ) with fluoride, chloride, bromide, iodide, and azide ions gave the corresponding 4′-derivatives 10 , 12 , 14 , 18 , and 20 , respectively. Reduction of 4-chloro-4-deoxy-α- d -galactopyranosyl 4-bromo-1,6-dichloro-1,4,6-trideoxy-β- d -fructofuranoside ( 15 ) gave 4-chloro-4-deoxy-α- d -galactopyranosyl 1,6-dichloro-1,4,6-trideoxy-β- d -fructofuranoside ( 16 ). A similar reduction of 4-chloro-4-deoxy-α- d -galactopyranosyl 4-azido-1,6-dichloro-1,4,6-trideoxy-β- d -fructofuranoside ( 21 ) gave 4-chloro-4-deoxy-α- d -galactopyranosyl 4-amino-1,6-dichloro-1,4,6-trideoxy-β- d -fructofuranoside ( 22 ).

Halogenation reactions of derivatives of D-glucose and sucrose

Treatment of methyl 4,6-O-benzylidene-alpha-D-glucopyranoside (1) with triphenylphophine-carbon tetrachloride-pyridine (reagent A) gave methyl 4,6-O-benzylidene-2-chloro-2-deoxy-alpha-D-mannopyranoside (2). When reagent A was used in excess, a further elimination reaction occurred to give methyl 4,6-O-benzylidene-2-chloro- (6, 60%) and -3-chloro-2,3-dideoxy-alpha-D-erythro-hex-2-enopyranoside (7, 16%). Treatment of 1 with triphenylphosphine-carbon tetrabromide-pyridine (reagent B) caused little or no elimination, and 47% of methyl 4,6-O-benzylidene-2-bromo-2-deoxy-alpha-D-mannopyranoside (14) was obtained. On treatment with reagent A, methyl alpha-D-glucopyranoside (16) gave exclusively methyl 2,4,6-trichloro- 2,3,4,6-tetradeoxy-alpha-D-erythro-hex-2-enopyranoside (17), and methyl 4,6-O-benzylidene-beta-D-glucopyranoside (19) gave methyl 4,6-O-benzylidene-3-chloro-3-deoxy-beta-D-allopyranoside (20, 70%). However, with reagent B, 19 gave methyl 4,6-O-benzylidene-3-bromo-3-deoxy-beta-D-glucopyranoside (23, 66%), probably by way of double inversion of configuration at C-3. Likewise, with reagent A, methyl beta-D-glucopyranoside (25) gave methyl 2,4,6-trichloro- (26) and3,4,6-trichloro-2,3,4,-6-tetradeoxy- beta-D-threo-hex-2-enopyranoside (27), and 4,6-O-isopropylidenesucrose (28) gave mainly 3-chloro-3-deoxy-4,6-O-isopropylidene-alpha-D-allopyranosyl 1,4,6-trichloro-1,4,6-trideoxy-beta-D-lyxo-hexulofuranoside (29) together with 3-chloro-3-deoxy-4,6-O-isopropylidene-alpha-D-allopyranosyl 1,4,6-trichloro-1,4,6-trideoxy-beta-D-fructofuranoside (30). The assignment of structure to 29 is tentative.