Selective deprotection of 2',6'-di-O-benzyl-2,3:5,6:3',4'-tri-O-isopropylidenelactose dimethyl acetal.
The reactivity order of O-deisopropylidenation of the three isopropylidene protecting groups of 2',6'-di-O-benzyl-2,3:5,6:3',4'-tri-O-isopropylidenelactose dimethyl acetal (2) with various reagents was established. The 5,6-acetal group was, although to a limited extent, more reactive as compared with the 3',4' group, while the 2,3-O-isopropylidene group was definitely less reactive. Conditions were determined for the direct preparation of the 5,6,3',4'-tetraol 5 (60% aqueous acetic acid, room temperature, 48 h, 73% yield) and the 5,6-diol 4 (propylene glycol and p-toluenesulphonic acid in dichloromethane, 46% yield). The diacetonated derivative 3, formally arising from a selective 3',4'-O-deisopropylidenation, was obtained in high yield (90%) through a selective acetonation with 2-methoxypropene of the tetraol 5.
Catelani
G
G
Dipartimento di Chimica Bioorganica e Biofarmacia, Università di Pisa, Italy. giocate@farm.unipi.it
D'Andrea
F
F
Puccioni
L
L
D000080:Acetals / Q000737:chemistry; D000475:Alkenes / Q000737:chemistry; D001593:Benzyl Compounds / Q000737:chemistry; D007785:Lactose / Q000031:analogs & derivatives* / Q000737:chemistry
C406480:2',6'-di-O-benzyl-2,3-5,6-3',4'-tri-O-isopropylidenelactose dimethyl acetal; D000080:Acetals; D000475:Alkenes; D001593:Benzyl Compounds; C013658:propylene; D007785:Lactose; C059033:1,1-dimethoxyethane