合成路线1

Reaction of 3-(benzyloxy)propionic acid (I) with 4(R)-isopropyl-1,3-thiazolidine-2-thione (II) in the presence of 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide hydrochloride and DMAP gives 3-[3-(benzyloxy)propanoyl]-4(R)-isopropyl-1,3-thiazolidine-2-thione (III), which by treatment with tin(II) trifluoromethanesulfonate and excess acetaldehyde affords 3-[(2S,3R)-2-(benzyloxymethyl)-3-hydroxybutanoyl]-4(R)-isopropyl-1,3-thiazolidine-2-thione (IV). Protection of the hydroxy group of (IV) with tert-butyldimethylsilyl chloride in the presence of imidazole yields 3-[(2S,3R)-2-(benzyloxymethyl)-3-(tert-butyldimethylsilyloxy)butanoyl]-4(R)-isopropyl-1,3-thiazolidine-2-thione (V), which is treated with p-anisidine to afford (2S,3R)-2-(benzyloxymethyl)-3-(tert-butyldimethylsilyloxy)-N-(4-methoxyphenyl)butylamide (VI). Deprotection of (VI) by hydrogenation with Pd/C in methanol-acetic acid gives (2S,3R)-3-(tert-butyldimethylsilyloxy)-2-(hydroxymethyl)-N-(4-methoxyphenyl)butylamide (VII), which is mesylated with methanesulfonyl chloride in the presence of triethylamine to yield (2S,3R)-3-(tert-butyldimethylsilyloxy)-2-[(methanesulfonyloxy)methyl]-N-(4-methoxyphenyl)butylamide (VIII). Cyclization of (VIII) with sodium hydride in CH2Cl2-DMF affords 3(S)-[1(R)-(tert-butyldimethylsilyloxy)ethyl]-1-(4-methoxyphenyl) azetidin-2-one (IX), the nitrogen atom of which is deprotected with cerium ammonium nitrate (CAN) in a mixture of acetonitrile-water to yield 3(S)-[1(R)-(tert-butyldimethylsilyloxy)ethyl]azetidin-2-one (X). Compound (X) is stereoselectively converted to (3S,4R)-3-[1(R)-(tert-butyldimethylsilyloxy)ethyl]-4-acetoxyazetidin-2-one (XI) on treatment with peracetic acid and ruthenium(III) chloride. Compound (XI) and 4(S)-ethyl-3-propionyl-1,3-thiazolidine-2-thione (XII) give, on treatment with tin(II) trifluoromethanesulfonate, (3S,4R)-3-[1(R)-(tert-butyldimethysilyloxy)methyl]-4-[1(R)-[4(S)-ethyl-2-thioxo-1,3-thiazolidin-3-ylcarbonyl]ethyl]azetidin-2-one (XIII) as the major diastereoisomer. Reaction of (XIII) with imidazole in acetonitrile gives (3S,4R)-3-[1(R)-(tert-butyldimethylsilyloxy)ethyl]-4-[1(R)-(imidazol-1-ylcarbonyl)ethyl]azetidin-2-one (XIV), which is treated with Mg(O2CH2CO2PNB)2 in acetonitrile to yield (3S,4R)-3-[1(R)-(tert-butyldimethylsilyloxy)ethyl]-4-[1(R)-methyl-3-(p-nitrobenzyloxycarbonyl)-2-oxopropyl]azetidin-2-one (XV). Compound (XV) is deprotected with hydrochloric acid in methanol to give (3S,4R)-3-[1(R)-hydroxyethyl]-4-[1(R)-methyl-3-(p-nitrobenzyloxycarbonyl)-2-oxopropyl]azetidin-2-one (XVI), which on diazotization with dodecylbenzenesulfonyl azide in acetonitrile yields (3S,4R)-4-[3-diazo-1(R)-methyl-3-(p-nitrobenzyloxycarbonyl)-2-oxopropyl]-3-[1(R)-hydroxyethyl]azetidin-2-one (XVII). Treatment of compound (XVII) with rhodium(II) octanoate in ethylacetate gives p-nitrobenzyl (1R,5R,6S)-6-[1(R)-hydroxyethyl]-1-methyl-2-oxocarbapenam-3-carboxylate (XVIII), which is reacted with diphenylchlorophosphate and diisopropylethylamine to afford p-nitrobenzyl (1R,5R,6S)-2-[(diphenylphosphono)oxy]-6-[1(R)-hydroxyethyl]-1-methylcarbapen-2-em-3-carboxylate (XIX).