1) The mesylation of 4(S)-hydroxypyrrolidin-2-one (I) with mesyl chloride and triethylamine in pyridine gives the corresponding ester (II), which is treated with potassium thioacetate (III) in refluxing acetonitrile yielding 4(R)-(acetylsulfanyl)pyrrolidin-2-one (IV). The hydrolysis of (IV) with sodium methoxide in methanol followed by acidification with aqueous HCl affords 4(R)-sulfanylpyrrolidin-2-one (V), which is condensed with (1R,5S,6S)-2-(diphenoxyphosphoryloxy)-6-[1(R)-hydroxyethyl]-1-methyl-1-carba-2-penem-3-carboxylic acid p-nitrobenzyl ester (VI) by means of ethyldiisopropylamine in acetonitrile to give (1R,5S,6S)-6-[1(R)-hydroxyethyl]-1-methyl-2-[5-oxopyrrolidin-3(R)-ylsulfanyl]-1-carba-2-penem-3-carboxylic acid p-nitrobenzyl ester (VII). The hydrogenolysis of (VII) with H2 over Pd/C in THF/aqueous phosphate buffer yields the sodium salt (VIII), which is finally esterified with pivaloyloxymethyl iodide (IX) in dimethylacetamide.
Protection of alcohol (I) with TBDMSCl and imidazole gives silyl compound (II) which is N-methylated by means of NaH and MeI and then deprotected with HCl to yield derivative (III). Mesylation of (III) with MsCl in presence of Et3N followed by thioacetylation with AcSK (A) affords thioacetate (IV) which is then hydrolyzed with NaOMe to yield (V). Treatment of (VI) with diphenylphosphoryl chloride (B) and DIEA in acetonitrile yields (VII), which is then condensed with mercaptan (V) by means of DIEA in the same solvent to provide carbapenem (VIII). Deprotection of the carboxyl moiety of (VIII) by hydrogenation with H2 over Pd/C affords carboxylate (IX), which is finally esterified with pivaloyloxymethyl iodide (X) in N,N-dimethylacetamide or DMF.
Alcohol (I) is protected with TBDMSCl and imidazole to give silyl compound (II), which is N-methylated by means of NaH and MeI and then deprotected with HCl to yield derivative (III). Mitsunobu reaction of (III) with 4-nitrobenzoic acid in presence of PPh3 and DEAD, followed by ester hydrolysis with K2CO3, provides alcohol (IV). Mesylation of (IV) with MsCl in presence of Et3N, followed by thioacetylation with AcSK (A), affords thioacetate (V), which is then hydrolyzed with NaOMe to yield (VI). Treatment of (VII) with diphenylphosphoryl chloride (B) in CH3CN and DIEA in CH3CN yields (VIII), which is then condensed with mercaptan (VI) by means of DIEA in the same solvent to provide carbapenem (IX). Deprotection of the carboxyl moiety of (IX) by hydrogenation with H2 over Pd/C affords carboxylate (X), which is finally esterified with pivaloyloxymethyl iodide (XI) in N,N-dimethylacetamide or DMF.