[CH2:1]1[S:5][CH2:4][NH:3][CH:2]1[C:6]([OH:8])=[O:7].C1(NC2CCCCC2)CCCCC1.O1CCOCC1.[C:28]([CH2:36][CH:37]([CH3:41])[C:38](O)=[O:39])(=[O:35])[C:29]1[CH:34]=[CH:33][CH:32]=[CH:31][CH:30]=1>C(#N)C>[C:28]([CH2:36][CH:37]([CH3:41])[C:38]([N:3]1[CH:2]([C:6]([OH:8])=[O:7])[CH2:1][S:5][CH2:4]1)=[O:39])(=[O:35])[C:29]1[CH:34]=[CH:33][CH:32]=[CH:31][CH:30]=1A mixture of 2.0 g. (0.015 mole) of L-thiazolidine-4-carboxylic acid and 2.72 g. (0.015 mole) of dicyclohexylamine is warmed on a steam bath. To the mixture is added 50 ml. of dioxane, 50 ml. of acetonitrile and 4.2 g. (0.015 mole) of 3-benzoyl-2-methylpropionic acid, N-hydroxysuccinimide ester (prepared from 3-benzoyl-2-methylpropionic acid N-hydroxysuccinimide and N,N-dicyclohexylcarbodiimide in tetrahydrofuran). The mixture is refluxed for 48 hours and concentrated in vacuo. The residue is dissolved in dichloromethane, washed with sodium bisulfate and extracted with saturated sodium bicarbonate. The basic extract is added to dilute hydrochloric acid and extracted with dichloromethane. The organic layer is dried over sodium sulfate and concentrated to an oil. The oil is crystallized from acetone-hexane to give [4R-(4R*,2'R*)]-3-(3-benzoyl-2-methylpropionyl)-4-thiazolidinecarboxylic acid as off-white crystals, m.p. 182°-183° C.; [α]D23 -63°±4 (c, 0.24, CH3OH).
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