Acetonation of Carbohydrates under Kinetic Control by Use of 2-Alkoxypropenes

Abstract

Polyols, as exemplified by the sugars and t h e i r derivatives, underso acetonation by 2-alkoxypropenes t o give cyclic acetals un3er k i n e t i c control.The products generally d i f f e r fro= those of conventional themadynamic acetonation ~n d c o n s t i t u t e c h i r a l l y s u b s t i t u t e d 1,j-dioxanes, 1,j-dioxolanes, and l a r g e r heterocycles, of wide p o t e n t i a l u t i l i t y i n synthesis.Free sugars r e a c t without tautomerization, and the hcmiacetal hydroxyl group does not generally take p a r t i n the reaction.The s t o i c h i o m t r y may be controlled t o give e i t h e r mono-o r di-acetals, and strained-ring acetals.0-Isopropylidenation (acetanation) of selected d i o l groups i n carbohydrates by use of acetone i n t h e presence of an a c i d c a t a l y s t and s desiccant bas long been established a s a valuable method