SnCl4 induced formation of C3-C11 alkenyl galactopyranosides as precursors for unsaturated neutral bolaforms

Abstract

The SnCl4 catalyzed glycosylation reaction of peracetylated ?-D-derivatives with terminally unsaturated C3?C11 alkenols was used for the synthesis of some C3?C11 alkenyl ?-D-galactopyranosides, as precursors for unsaturated neutral bolaforms.

Microwave-assisted synthesis of long-chain alkyl glucopyranosides

“…[7][8][9][10][11] By this methodology, it is usual to obtain a mixture of four isomers: the kinetic furanosides and the thermodynamic pyranosides with the major axial anomeric configuration. A protected glucose is used in the Koenigs-Knorr [12][13][14][15] and the Helferich [15][16][17][18][19][20][21][22] glycosylations of fatty alcohols. The two methodologies allow the synthesis of alkyl glucosides in high yield avoiding the formation of furanoside isomers.…”

“…Some Lewis acids favour the synthesis of the kinetic b anomer, [15][16][17] while others result in the thermodynamic a anomer. 13,14,[18][19][20][21][22] However, synthesis of the a anomer as the major isomer or conversion of the b anomer into the a anomer require long reaction times, up to a few days. [18][19][20][21][22] Compared to conventional methods, reactions under microwaves usually show noticeable improvements such as shorter reaction times, high yields and these can be carried out in solvent-free conditions.…”

“…13,14,[18][19][20][21][22] However, synthesis of the a anomer as the major isomer or conversion of the b anomer into the a anomer require long reaction times, up to a few days. [18][19][20][21][22] Compared to conventional methods, reactions under microwaves usually show noticeable improvements such as shorter reaction times, high yields and these can be carried out in solvent-free conditions. Microwave-assisted Fischer glycosylation is feasible for short chain alcohols, 9,10 but in the case of fatty alcohols (octanol 10 and decanol 11 ), yields can be diminished due to decomposition of glucosides.…”