Process improvement in the preparation of (4r, 5s, 6s)-3-[[(2r,3r)-2-[[[(s)-2-amino-3-methyl-1-oxobutyl]amino]methyl]tetrahydro-3-furanyl]thio]-6-[(r)-1-hydroxyethyl]-4-methyl-7-oxo-1-azabicyclo[3.2.0]hept-2-ene-2-carboxylic acid

A process for producing (4R, 5S, 6S)-3-[[(2R,3R)-2-[[[(S)-2-amino-3-methyl-1-oxobutyl]amino]methyl]tetrahydro-3-furanyl]thio]-6-[(R)-1-hydroxyethyl]-4-methyl-7-oxo-1-azabicyclo [3.2.0]hept-2-ene-2-carboxylic acid which comprises:

• dissolving 4-nitrobenzyl (4R,5S,6S)-6-[(1R)-1-hydroxyethyl]-4-methyl-3-{[(2R,3R)-2-({[(2S)-3-methyl-2-({[(4-nitrobenzyl)oxy]carbonyl}amino)-butanoyl]amino}methyl)tetrahydrofuran-3-yl]thio}-7-oxo-1-azabicyclo[3.2.0]hept-2-ene-2-carboxylate in ethyl acetate;
• adding sufficient water forming about a 1:1 ethyl acetate:water biphasic solvent system;
• hydrogenation of a reaction mixture of 4-nitrobenzyl (4R,5S,6S)-6-[(1R)-1-hydroxyethyl]-4-methyl-3-{[(2R,3R)-2-({[(2S)-3-methyl-2-({[(4-nitrobenzyl)oxy]carbonyl}amino)butanoyl]amino }methyl)tetrahydrofuran-3-yl]thio}-7-oxo-1-azabicyclo[3.2.0]hept-2-ene-2-carboxylate and about a 1:1 ethyl acetate:water biphasic solvent system, said biphasic solvent system further characterized as not including an acid acceptor in addition to 4-nitrobenzyl (4R,5S,6S)-6-[(1R)-1-hydroxyethyl]-4-methyl-3-{[(2R,3R)-2-({[(2S)-3-methyl-2-({[(4-nitrobenzyl)oxy]carbonyl}amino)butanoyl]amino}methyl)tetrahydrofuran-3-yl]thio}-7-oxo-1-azabicyclo[3.2.0]hept-2-ene-2-carboxylate and (4R, 5S, 6S)-3-[[(2R,3R)-2-[[[(S)-2-amino-3-methyl-1-oxobutyl]amino]methyl]tetrahydro-3-furanyl]thio]-6-[(R)-1-hydroxyethyl]-4-methyl-7-oxo-1-azabicyclo[3.2 0]hept-2-ene-2-carboxylic acid;
• said hydrogenation resulting in the formation of(4R, 5S, 6S)-3-[[(2R,3R)-2-[[[(S)-2-amino-3-methyl-1-oxobutyl]amino]methyl]tetrahydro-3-furanyl]thio]-6-[(R)-1-hydroxyethyl]-4-methyl-7-oxo-1-azabicyclo[3.2.0]hept-2-ene-2-carboxylic acid, 4-methylaniline and carbon dioxide, wherein said 4-methylaniline is miscible in the ethyl acetate organic solvent portion of said biphasic solvent system and the carbon dioxide and (4R, 5S, 6S)-3-[[(2R,3R)-2-[[[(S)-2-amino-3-methyl-1-oxobutyl]amino]methyl]-tetrahydro-3-furanyl]thio]-6-[(R)-1-hydroxyethyl]-4-methyl-7-oxo-1-azabicyclo[3.2.0]hept-2-ene-2-carboxylic acid are miscible in the water portion of said biphasic solvent system;
• upon completion of said hydrogenation, separating the water portion from said ethyl acetate portion and isolating (4R, 5S, 6S)-3-[[(2R,3R)-2-[[[(S)-2-amino-3-methyl-1-oxobutyl]amino]methyl]tetrahydro-3-furanyl]thio]-6-[(R)-1-hydroxyethyl]-4-methyl-7-oxo-1-azabicyclo[3.2.0]hept-2-ene-2-carboxylic acid from said separated water portion by lyophilization or reverse osmosis.