Hexopyranose alkylation

Fully acetylated hexopyranoses react with thiols in the presence of Lewis acids, such as BF3-Et20.32,33 The reaction is faster with 1,2-trans acetates than with the corresponding 1,2-cij ones and 1,2-trans products predominate. Alkyl, alkenyl, and aryl thioglycosides are produced by this method. Variations on this method include the use of trimethylsilyl34 or stannyl derivatives35 of the thiols. 

Li, X, Ohtake, Ft, Takahashi, Ft, Ikegami, S, A facile synthesis of I -C-alkyl-a-disaccharides from 1-C-alkyl-hexopyranoses and methyl 1-C-methylhexopyranosides, Tetrahedron, 57, 4297-4309, 2001. 

Carolinoside (1), isolated from Solanum carolinense as the host plant specific feeding induction factor for Manduca sexta, has been further characterised and shown to incorporate a 2,6-dideoxy-3-C-methyl- -L-flra6/ o-hexopyranose unit. Alkylation (LDA/Mel) of ketone (2) has afforded the 3-C-methyl derivative (3) which was converted to the A/ -benzylformamide compound (4), an TV-forraylkanosamine glycosyl donor. Aldol condensation (LDA/THF) of ester (5) with aldehyde (6) produced predominantly the isomer (7) which was converted into L-cladinose (8). An aldol condensation of mi s-but-2-enal with a ketene thioacetal has been employed with a chiral catalyst in a preparation of 4-C-methyl-D-ribose/... 

Conformational Studies. - Conformation analysis on various 2,3,6-trideoxy-3-amino-a-L-hexopyranoses and their iV-alkylated derivatives revealed that the C4-conformation was favoured. ... 

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