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 () and its 6,7-diepi isomer () in a stereocontrolled manner, is reported herein. An appropriately protected polyhydroxylated pyrrolidine, such as (2R,3R,4R,5R)-3,4-dibenzyloxy-2′-O-tert-butyldiphenylsilyl-2,5-bis(hydroxymethyl)pyrrolidine (, protected DMDP), easily available from d-fructose, was chosen as the chiral starting material. Compounds and were obtained from , in seven steps, in a 23.2 and 20.5% overall yields, respectively.