Chiral Pool Synthesis of trans-(2S,3S)-3-Hydroxyproline and Castanodiol from S-Pyroglutamic Acid.

Article abstract of DOI:10.1016/S0957-4166(00)80492-9

The Pyroglutamic acid derivative 1 was converted through several steps into Castanodiol 9 and 2S,3S-3-Hydroxyproline 11.Key steps of the reaction sequence were the stereoselective epoxidation of 1 to 2 and the regioselective ring opening of 2 to 3.BH3*S(CH3)2 reduction of the amide group of 3 and 4 resulted in a concomitant transformation of the acetal moiety into the N-benzyl protecting group.The air sensitive 5 and 6, were transformed to the stable N-Boc prolinol derivatives 7 and 8.Deprotection of 8 provided 9, while oxidation of 8 gave the protected proline derivative 10.Deprotection of 10 furnished enantiopure 2S,3S-3-Hydroxyproline 11.