1-O-BENZYL-BETA-L-ARABINOPYRANOSE, ENZYL-3,4-O-ISOPROPYLIDENE-BETA-L-ARABINO-PYRANOSE AND ENZOYL-3,4-O-ISOPROPYLIDENE-BETA-L-ARABINOPYRANOSE

The sugar ring of 1-O-benzyl-beta-L-arabinopyranose (C12H16O5), (I), a dopts the C-4(1) chair conformation. In benzyl-3,4-O-isopropylidene-be ta-L-arabinopyranose (C15H20O5), (II), and enzoyl-3,4-O-isopropylidene -beta-L-arabinopyranose (C22H24O6), (III), the pyranosyl rings have ch air C-4(1) conformations slightly distorted towards H-0(1) conformatio ns. In both (II) and (III), the five-membered isopropylidene ring adop ts a slightly distorted envelope conformation. The methylene C atoms o f the benzyl group are slightly displaced out of the plane of the phen yl ring in all three crystal structures. All three hydroxy groups in ( I) participate in hydrogen bonds, each as donor and acceptor simultane ously, forming a two-dimensional hydrogen-bond network. In (II), molec ules linked by hydrogen bonds form polymeric chains along the b axis.