Efficient preparations both of 2,3:5,6:3',4'-tri-O-isopropylidenelactose dimethyl acetal (5, 95% yield) and its 6'-O-(1-methoxy-l-methylethyl) derivative (65% yield), useful intermediates for the conversion of lactose into biologically relevant oligosaccharides, by 'one-pot' acetonation procedures with 2,2-dimethoxypropane are reported. The acetonation of 5 with 2-methoxypropene in the presence of pyridinium tosylate and 4 A molecular sieves unexpectedly revealed the formation, in a first kinetic reaction phase, of similar amounts of the 2'-0- and 6'-O-(1-methoxy-l-methylethyl) acetals. The structures of all new products were fully characterized by NMR analyses, which also allowed some deductions on the conformation of the galactopyranosyl rings.
Improved preparation of 2,3:5,6:3',4'-tri-O-isopropylidenelactose dimethyl acetal and its 6'-O-(1-methoxy-1-methylethyl) derivative
CATELANI, GIORGIO;D'ANDREA, FELICIA;
1997-01-01
Abstract
Efficient preparations both of 2,3:5,6:3',4'-tri-O-isopropylidenelactose dimethyl acetal (5, 95% yield) and its 6'-O-(1-methoxy-l-methylethyl) derivative (65% yield), useful intermediates for the conversion of lactose into biologically relevant oligosaccharides, by 'one-pot' acetonation procedures with 2,2-dimethoxypropane are reported. The acetonation of 5 with 2-methoxypropene in the presence of pyridinium tosylate and 4 A molecular sieves unexpectedly revealed the formation, in a first kinetic reaction phase, of similar amounts of the 2'-0- and 6'-O-(1-methoxy-l-methylethyl) acetals. The structures of all new products were fully characterized by NMR analyses, which also allowed some deductions on the conformation of the galactopyranosyl rings.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
