334
2
General Synthetic Methods
⊡ Scheme 53
⊡ Scheme 54
alcohol, obtained the corresponding 2-C-methylene glycosides 198a and 198b, respectively, in
good yields and exclusive α-selectivity. The excellent yields and exclusive α-selectivity were
also obtained in the reactions of 2-C-acetoxymethyl-3,4,6-tri-O-methyl-D-galactal with benzyl, allyl, and tert-butyl alcohols. Interestingly, the reaction of 2-C-acetoxyglycals 197a (or
197b) with phenols formed the corresponding chiral carbohydrate-pyranobenzopyran derivatives 199a (or 199b) via Ferrier rearrangement and tandem cyclization in excellent yields and
moderate to high stereoselectivities.
2
General Synthetic Methods
⊡ Scheme 53
⊡ Scheme 54
alcohol, obtained the corresponding 2-C-methylene glycosides 198a and 198b, respectively, in
good yields and exclusive α-selectivity. The excellent yields and exclusive α-selectivity were
also obtained in the reactions of 2-C-acetoxymethyl-3,4,6-tri-O-methyl-D-galactal with benzyl, allyl, and tert-butyl alcohols. Interestingly, the reaction of 2-C-acetoxyglycals 197a (or
197b) with phenols formed the corresponding chiral carbohydrate-pyranobenzopyran derivatives 199a (or 199b) via Ferrier rearrangement and tandem cyclization in excellent yields and
moderate to high stereoselectivities.