The Chemistry of Isopropenyl Glycopyranosides. Transglycosylations and Other Reactions
摘要:
Various anomerically pure isopropenyl alpha- and beta-glycopyranosides have been synthesized and shown to undergo synthetically useful transglycosylation reactions with a variety of primary and secondary carbohydrate alcohols. Although stable when stored, isopropenyl glycosides are readily activated as glycosyl donors by a variety of electrophiles, including N-iodosuccinimide/triflic acid, trimethylsilyl triflate, and triflic anhydride. Under conditions that retard formation of the glycosyl cation, the reactivity of isopropenyl glycosides is diverted away from transglycosylation and toward electrophilic addition across the vinyl ether double bond.
The Chemistry of Isopropenyl Glycopyranosides. Transglycosylations and Other Reactions
摘要:
Various anomerically pure isopropenyl alpha- and beta-glycopyranosides have been synthesized and shown to undergo synthetically useful transglycosylation reactions with a variety of primary and secondary carbohydrate alcohols. Although stable when stored, isopropenyl glycosides are readily activated as glycosyl donors by a variety of electrophiles, including N-iodosuccinimide/triflic acid, trimethylsilyl triflate, and triflic anhydride. Under conditions that retard formation of the glycosyl cation, the reactivity of isopropenyl glycosides is diverted away from transglycosylation and toward electrophilic addition across the vinyl ether double bond.
Amphiphilic glucosyl acetone-based ketal-linked etoposide glycoside prodrug isomers were synthesized and fabricated into excipient-free nanoparticles for effective cancer prodrug monotherapy. Hydrolysis of the glycosidic linkage or the ketal linkage triggered hydrolysis of the other linkage, which resulted in spontaneous self-immolative hydrolysis of the prodrugs. Nanoparticles of the prodrug isomer that
Isopropenyl glycosides (i.e., 10 and 11) have been synthesized in high yields by reacting the corresponding anomeric acetates with the Tebbe reagent. These compounds undergo glycosylation with primary or secondary carbohydrate alcohols in the presence of trimethylsilyl triflate or boron trifluoride etherate, probably via a mixed acetal glycoside intermediate. On the basis of this principle, a quite efficient glycosylation of monosaccharide hemiacetal donors (i.e., 1, 7, and 9) with acceptors bearing an isopropenyl ether function at a primary or secondary position (i.e., 18 and 21) has been developed. Also investigated were the glycosylating properties of isopropenyl glucosyl and galactosyl carbonates (i.e., 12-15), easily prepared from the corresponding hemiacetals, toward sugar alcohols. In each case, the beta-selective synthesis of disaccharides from donors having nonparticipating groups at C-2 was ensured by the use of acetonitrile, at low temperature, as the solvent.
The Chemistry of Isopropenyl Glycopyranosides. Transglycosylations and Other Reactions
作者:H. Keith Chenault、Alfredo Castro、Laura F. Chafin、Jie Yang
DOI:10.1021/jo960190p
日期:1996.1.1
Various anomerically pure isopropenyl alpha- and beta-glycopyranosides have been synthesized and shown to undergo synthetically useful transglycosylation reactions with a variety of primary and secondary carbohydrate alcohols. Although stable when stored, isopropenyl glycosides are readily activated as glycosyl donors by a variety of electrophiles, including N-iodosuccinimide/triflic acid, trimethylsilyl triflate, and triflic anhydride. Under conditions that retard formation of the glycosyl cation, the reactivity of isopropenyl glycosides is diverted away from transglycosylation and toward electrophilic addition across the vinyl ether double bond.