Higher Sucrose Analogs: Homologation of a Glucose Unit of Sucrose by Two Carbon Atoms
摘要:
The primary hydroxyl groups (at C-6 and C-6') in 2,3,4,3'4'-penta-O-benzyl-1'-O-methoxymethyl sucrose (2) can be reactively differentiated with tert-butyldiphenylsilyl chloride. Reaction of 2 with TBDPSCl afforded only one monosilylated product protected at C-6' (6). The regioisomeric monoprotected sucrose 8 was prepared by selective deprotection of the double silylated derivative 7. Compound 6 was converted into 2,3,4,3',4'-penta-O-benzyl-6-carbomethoxymethylidene-1'-O-methoxymethylsucrose 10 in three steps. Osmylation of the double bond in 10 afforded stereoisomeric homologated sucroses: 11a [6(S),7(R)] and 11b [6(R),7(S)] in the ratio 3:2. A large downfield shift of the H-1 (up to 0.5 ppm) was observed for 6'-silylated derivatives.
Higher Sucrose Analogs: Homologation of a Glucose Unit of Sucrose by Two Carbon Atoms
摘要:
The primary hydroxyl groups (at C-6 and C-6') in 2,3,4,3'4'-penta-O-benzyl-1'-O-methoxymethyl sucrose (2) can be reactively differentiated with tert-butyldiphenylsilyl chloride. Reaction of 2 with TBDPSCl afforded only one monosilylated product protected at C-6' (6). The regioisomeric monoprotected sucrose 8 was prepared by selective deprotection of the double silylated derivative 7. Compound 6 was converted into 2,3,4,3',4'-penta-O-benzyl-6-carbomethoxymethylidene-1'-O-methoxymethylsucrose 10 in three steps. Osmylation of the double bond in 10 afforded stereoisomeric homologated sucroses: 11a [6(S),7(R)] and 11b [6(R),7(S)] in the ratio 3:2. A large downfield shift of the H-1 (up to 0.5 ppm) was observed for 6'-silylated derivatives.