文摘
The large-scale synthesis of Swainsonine 1, a potent α-mannosidase II inhibitor, has been achieved with several improvements. The key modifications were (a) performing the Wittig olefination under mild conditions and isolation of the product 4 with modified workup conditions, (b) introduction of the azido group on a large scale under Mitsunobu conditions to produce 12, (c) performing the 1, 3-dipolar cycloaddition of an unactivated azide 12 to afford the imino carboxylic ester 7, (d) formation of amide 10 from 7 under mild acidic conditions, and (e) isolation of the final compound 1 as a stable hydrochloride salt. In addition, synthesis of 11 was accomplished from 12 by telescoping the four steps.