[C:1]([O-])(=[O:5])[CH:2]([CH3:4])[OH:3].[Na+].C1(P(N=[N+]=[N-])(C2C=CC=CC=2)=O)C=CC=CC=1.C(N(CC)CC)C.Cl.[NH:33]1[CH2:47][CH2:46][CH2:45][C@H:34]1[C:35]([O:37][CH2:38][C:39]1[CH:44]=[CH:43][CH:42]=[CH:41][CH:40]=1)=[O:36]>CN(C)C=O>[OH:3][C@@H:2]([CH3:4])[C:1]([N:33]1[CH2:47][CH2:46][CH2:45][C@H:34]1[C:35]([O:37][CH2:38][C:39]1[CH:40]=[CH:41][CH:42]=[CH:43][CH:44]=1)=[O:36])=[O:5]A mixture of sodium lactate (1.7 g., 15.0 mmole), diphenylphosphorylazide (3.6 ml., 1.1 eq.), and dry dimethylformamide (30 ml.) at 0° (ice-bath) in an argon atmosphere is treated with triethylamine (2.1 ml., 1.0 eq.) and L-proline, phenylmethyl ester, monohydrochloride salt (3.6 g., 15.0 mmole). After 24 hours, the reaction mixture is partitioned between ethyl acetate and water. The aqueous phase is back extracted, the organic extracts are combined, washed with 5% potassium bisulfate, brine, and evaporated. The residue (5 g.) is chromatographed on silica (130 g.) eluting with (1:1, ethyl acetate/hexane) to give 2.5 g. of 1-[(S)-2-hydroxy-1-oxopropyl]-L-proline, phenylmethyl ester as a white crystalline solid after evaporation; m.p. 86°-88° (isopropyl ether). TLC (silica gel; ethyl acetate) Rf =0.4.
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