合成路线1

The thiol (II) has been obtained as follows: The aldehyde (V), which is synthesized from trans-4-hydroxy-L-proline in several steps (3), reacts with the lithium enolate of the pyrrolidone (IV) to afford the alcohol (VI) and its diastereomeric isomers. After purification on a silica gel column, reduction of (VI) by borane-dimethylsulfide in refluxing THF gives (VII). Removal of the amino protecting groups of (VII) by TFA, followed by reprotection with PNZ groups and then removal of the tert-butyldimethylsilyl group with Bu4NF gives the diol (VIII). Selective mesylation of (VIII), followed by reaction with potassium thioacetate, gives (IX), which is treated with aqueous 1 N NaOH in methanol to afford the thiol (II).