water and then dried mgso 4 the solvent was evaporated in vacuo to dryness the residue was chromatographed on silica gel 40 g using chcl 3 acetone 19 1 as eluants appropriate fractions were pooled and solvents were removed in vacuo to dryness giving 350 mg of the above titled compound tlc silica gel chcl 3 acetone 4 1 rf 0 77 n t butoxycarbonyl s acetamidomethyl penicillaminyl 2 3 dimethylanilide was treated with 50 tfa in ch 2 cl 2 20 ml for 30 min volatile substances were removed in vacuo to dryness trace of tfa was removed by co evaporation with toluene several times the tfa salt was dissolved in chcl 3 30 ml treated with excess triethylamine washed with water dried mgso 4 and solvent was evaporated in vacuo to give free base to a stirred solution of 2 r t butoxycarbonylamino 3 triphenylmethylmercaptopropanal 0 5 g example 1b and l s acetamidomethylpenicillaminyl 2 3 dimethylanilide tfa salt 0 3 g in meoh containing 1 acetic acid hoac 10 ml was added portionwise nacnbh 3 100 mg the mixture was stirred at room temperature overnight most of the solvent was evaporated in vacuo to a small volume which was partitioned between etoac and water etoac layer was further washed with aqueous nahco 3 water and then dried mgso 4 after evaporation of solvent the residue was chromatographed on silica gel 30 g using chcl 3 acetone 19 1 to 9 1 as eluants appropriate fractions were pooled and solvents were evaporated in vacuo to dryness giving 360 mg of the above.