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Synthesis, conformation and glycosylation reaction of substituted 2,6-dioxabicyclo[3.1.1]heptanes:1,3-anhydro-2,4-di-O-benzyl-α-l-arabinopyranose

✍ Scribed by Yuguo Du; Fanzuo Kong

Publisher
Elsevier Science
Year
1995
Tongue
English
Weight
875 KB
Volume
275
Category
Article
ISSN
0008-6215

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✦ Synopsis

The title 1,3-anhydro sugar (10) was obtained as crystals by the ring closure of 3-O-acetyl-2,4di-O-benzyl-a,[3-L-arabinopyranosyl chloride (9) which was prepared from methyl fl-Larabinopyranoside via a sequence of reactions involving initial selective 3-O-allylation. Methanolysis of 10 gave 1,3-c/s arranged methyl 2,4-di-O-benzyl-a-L-arabinopyranoside as the major product. Glycosylation of 10 with 1,2:3,4-di-O-isopropylidene-a-D-galactopyranose or with serine derivatives resulted in the same stereochemical outcome, while glycosylation of the 1,3-anhydro galacto-( 19) and manno-pyranose (24) analogues afforded predominantly 1,3-trans ring opening products. Conformational analysis of 10, 19 and 24 revealed that the C-5 head of 10 is flexible. The conformation of 10 in solution is close to E 2 while 19 and 24 prefer the B2, 5 form.

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