Polyhydroxylated pyrrolizidines.: Part 6:: A new and concise stereoselective synthesis of (+)-casuarine and its 6,7-diepi isomer, from DMDP

A new synthesis for (+)-casuarine (1) and its 6,7-diepi isomer (15) in a stereocontrolled manner, is reported herein. All appropriately protected polyhydroxylated pyrrolidine, such as (2R,3R,4R,5R)-3,4-dibenzyloxy-2'-O-tet-t-butyldiphenylsilyl-2,5-bis(hydroxymethl)pyrrolidine (3, protected DMDP), easily available from D-fructose, was chosen as the chiral starting material. Compounds 1 and 15 were obtained from 3, in seven steps, in a 23.2 and 20.5% overall yields, respectively. (c) 2005 Elsevier Ltd. All rights reserved.