STEREOSELECTIVE EPOXIDATION OF DIVINYLMETHANOL: A SYNTHETIC APPROACH TO THE PENTITOLS

Article abstract of DOI:10.1016/S0008-6215(00)81036-8

Peroxy-acid epoxidation of divinylmethanol (9), followed by acetylation afforded the acetylated monoepoxides 1 and 2 having the erythro (53percent) and threo (47percent) configurations.Peroxy-acid epoxidation of 1 and 2 yielded the acetylated diepoxides 3 (erythro-erythro, 36percent) and 4 (erythro-threo, 64percent) (from 1), and 4 (erythro-threo, 47percent) and 5 (threo-threo, 53percent) (from 2).Relative configurational assignments were made to 1-5 on the basis of (a) (1)H-n.m.r. chemical-shift and coupling-constant data, (b) the observation that 1 gave only 3 and 4, and that 2 gave only 4 and 5 on epoxidation, and (c) the fact that 3-5 separately undergo epoxidering opening preferentially at their primary carbon atoms with acetate ion in acetic anhydride, to afford the penta-acetates of ribitol, DL-arabinitol, and xylitol, respectively, as major products.Epoxide-ring formation favours the erythro configuration when either peroxy acids or tert-butyl hydroperoxide with catalitically active Ti(4+), V(5+), or Mo(6+) complexes are employed as epoxidation reagents.However, the diastereoselectivities characterising the epoxidations and the regioselectivities governing the epoxide-ring openings are not sufficiently high to constitute an attractive synthesis of euther ribitol, DL-arabinitol, or xylitol from divinylmethanol.