[O:1]([CH2:8][C:9](=O)[C:10]([OH:12])=[O:11])[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.O(CC(OCC)=O)C1C=CC=CC=1.C(OCC)(=O)C(OCC)=O.[NH2:37][C@H:38]([C:40]([N:42]1[CH2:49][CH2:48][CH2:47][C@H:43]1[C:44]([OH:46])=[O:45])=[O:41])[CH3:39].[OH-].[Na+].[BH3-]C#N.[Na+]>O>[C:10]([CH:9]([NH:37][C@H:38]([C:40]([N:42]1[CH2:49][CH2:48][CH2:47][C@H:43]1[C:44]([OH:46])=[O:45])=[O:41])[CH3:39])[CH2:8][O:1][C:2]1[CH:3]=[CH:4][CH:5]=[CH:6][CH:7]=1)([OH:12])=[O:11]A slurry of phenoxypyruvic acid (1.8 g) (prepared by the condensation of ethyl phenoxyacetate with diethyl oxalate, followed by acid catalyzed hydrolysis and decarboxylation) and L-alanyl-L-proline (0.37 g) in 10 ml of water is adjusted to pH 7 with dilute NaOH. The mixture is treated with NaBH3CN (0.18 g) and allowed to stir at room temperature for 5 days. On the second and third days additional ketoacid (0.9 g) and sodium cyanoborohydride (0.18 g) are added. The product is adsorbed on strong acid ion-exchange resin and eluted with 2% pyridine in water to yield, after freeze-drying, 0.5 g of N-(1-carboxy-2-phenoxyethyl)-L-alanyl-L-proline. The nmr is consistent with structure. The mass spectrum shows a peak at 479 for the silylated molecular ion minus methyl (494-15).
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