Two Total Syntheses of Showdomycin and Related Studies

After a series of model reactions, D-ribose (2) was reacted with 3-(triphenylphosphoranylidene)-2, 5-pyrrolidinedione (8a) in THF at reflux to produce 3(E)-(2(S), 3(S), 4(R), 5-tetrahydroxy-1-pentylidene)-2, 5-pyrrolidinedione (35) (75%). Subsequent cyclization of 35 using phenylselenenyl chloride followed by hydrogen peroxide gave showdomycin (1) (13%) and epi-showdomycin (36) (41%). Using a similar strategy 2, 3-O-iso-propylidene-D-ribose (37b) was reacted sequentially with 1-(triphenylmethyl)-3-(triphenylphosphoranylidene)-2, 5-pyrrolidinedione (8b), phenylselenenyl chloride, hydrogen peroxide, and trifluoroacetic acid to give 1 (3% overall).