Chelation-Assisted C-O Bond Cleavage of Ortho Esters. A Convenient Synthesis of myo-Inositol Derivatives Having Free Hydroxy Group(s) at Specific Position(s).
Reactions of ortho esters of myo-inositol 8 or 10 with 1-2 equiv of Grignard reagents in benzene-ether yield regio- and stereoselectively the corresponding ring opening products having a free hydroxy group at C-1. The regioselectivity is rationalized owing to the presence of the 2-methoxy group which will serve as an auxiliary to form a chelation complex 12 with magnesium. Inositol derivatives having two free hydroxy group at C-1 and C-3 positions can be achieved from reactions of 6 or 8 with excess Grignard reagents or under more drastic conditions. The reaction of 8b with excess LiAlH(4)/AlCl(3), on the other hand, yields the corresponding 1,5-diol 19.
Yeh
Sue-Min
SM
Department of Chemistry, National Taiwan University, Taipei, Taiwan 106, Republic of China.
Lee
Gene Hsiang
GH
Wang
Yu
Y
Luh
Tien-Yau
TY