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).

The condensation of the enolphosphate (I) (1) and the thiol (II) in the presence of diisopropylethylamine gives the protected compound (III), which is deprotected by hydrogenolysis with H2 over Pd(OH)2 on carbon, purified by reverse-phase silica gel chromatography and treated with HCl to afford ER-35786 (2), as shown in Scheme 22662001a.

The condensation of the enolphosphate (I) (1) and the thiol (II) in the presence of diisopropylethylamine gives the protected compound (III), which is deprotected by hydrogenolysis with H2 over Pd(OH)2 on carbon, purified by reverse-phase silica gel chromatography and treated with HCl to afford ER-35786 (2), as shown in Scheme 22662001a.

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).

The condensation of the enolphosphate (I) (1) and the thiol (II) in the presence of diisopropylethylamine gives the protected compound (III), which is deprotected by hydrogenolysis with H2 over Pd(OH)2 on carbon, purified by reverse-phase silica gel chromatography and treated with HCl to afford ER-35786 (2), as shown in Scheme 22662001a.