APPLICATION OF STABILIZED SUGAR-DERIVED PHOSPHORANES IN THE SYNTHESISOF HIGHER CARBON MONOSACCHARIDES - FIRST SYNTHESIS OF A C-21-DIALDOSE

C-21 Monosaccharide precursors 11 and 12 were synthesized by a couplin g of a C-12 aldehyde 1 with C-9 stabilized phosphoranes 2 and 3 respec tively. The ''smaller'' C-19 sugar 13 was prepared from a C-12 aldehyd e 1 and C-7 phosphorane 4. All reactions with phosphoranes were perfor med under high pressure (13 kbar). No reaction was observed under norm al pressure even at high temperature (ca 140 degrees C). The synthesis of C-19 and C-21 monosaccharides was accomplished also under normal p ressure when phosphoranes were replaced with more nucleophilic phospho nates; however, partially eliminated products (M-benzyl alcohol) were isolated together with higher sugar enones 11, 12 and 13. Sugar alpha- hydroxy-aldehydes (14) did not react with a C-9-phosphorane even under 13 kbar pressure, although reaction with a shorter analog - C-7 phosp horane 15 proceeded under normal pressure in boiling benzene. (C) 1998 Elsevier Science Ltd. All rights reserved.