Asymmetric synthesis of the spiroacetal fragment of milbemycin E
Abstract
Spiro-acetals (17) and (21) have been synthesized from methyl α-D-glucopyranoside (11), via the 6-chloro-4,6-dideoxygalactopyranoside (10), the epoxy-dithiane (8), and the open-chain dithianes (16) and (20).