The acetonation of methyl 5-C-methoxy-β-d-galactopyranoside with 2,2-dimethoxypropane

The acetonation of methyl 5-C-methoxy-β-d-galactopyranoside (1a), masked bis-glycoside form of l-arabino-hexos-5-ulose, with a large excess of 2,2-dimethoxypropane and catalytic amounts of p-toluenesulfonic acid gives a mixture of five acetonides. The most abundant isolated product was the mixed acetal methyl 6-O-(1–methoxy-1-methylethyl)-3,4-O-isopropylidene-5-C-methoxy-β-d–galactopyranoside (44% yield).