THE PAECILIN PUZZLE - ENANTIOSELECTIVE SYNTHESES OF THE PROPOSED STRUCTURES OF PAECILIN A AND B

摘要

For the synthesis of the two diastereomers 3c and 3d of the proposed structure of paecilin B (3) phenol 19, containing an alkenyl moiety, was treated with Pd(II) in the presence of the chiral BOXAX ligand 9b to give 20 with 96% ee. A subsequent Sharpless dihydroxylation afforded two isomeric diols, which were further transformed into 31 and 32. The final steps included removal of the silyl protecting group with simultaneous lactone formation, oxidation and cleavage of the methyl ether. For the preparation of the dimeric paecilin A (1) brominated intermediate 38 was treated with (Bpin)_2, S-Phos and Pd(OAc)_2. The spectroscopic data of the new compounds did not match those of the isolated natural products.