C(N[CH:5]([CH3:7])C)(C)C.C([Li])CCC.[CH3:13][P:14]([CH3:21])(=[O:20])[O:15][CH2:16][CH:17]([CH3:19])[CH3:18].[C:22]([O:26][C:27]([NH:29]NCC(OC)=O)=[O:28])([CH3:25])([CH3:24])[CH3:23].C(=O)(O)[O-:37].[Na+]>O1CCCC1.CCCCCC.C(O)(=O)C>[C:22]([O:26][C:27]([NH:29][CH2:7][C:5](=[O:37])[CH2:13][P:14]([CH3:21])(=[O:20])[O:15][CH2:16][CH:17]([CH3:19])[CH3:18])=[O:28])([CH3:23])([CH3:24])[CH3:25]To a solution of 6.1 g of diisopropylamine in 25 ml of dry tetrahydrofuran at 0° under an atmosphere of nitrogen are added 37.5 ml of a 1.6M solution of n-butyllithium in hexane. This solution is stirred for a period of 10 minutes and then cooled to -78°. To this is added, via a syringe, a solution of 9.0 g of isobutyl P,P-dimethyl-phosphinate in 50 ml of dry tetrahydrofuran and the mixture is stirred at -78° for a period of 1 hour. To this is then added a solution of 1.9 g of methyl N-tert.-butoxycarbonylaminoglycinate in 25 ml of dry tetrahydrofuran and the reaction mixture is allowed to warm to room temperature and is stirred for a period of 1 hour. 3 ml of glacial acetic acid are then introduced, followed by 50 ml of saturated sodium bicarbonate solution, and the aqueous layer is extracted twice with 100 ml of ether. The organic extract is dried over magnesium sulphate and concentrated under reduced pressure. The residue is chromatographed on silica gel using ethyl acetate as eluent. There is obtained isobutyl P-(3-t-butoxycarbonylamino-2-oxo-propyl)-P-(methyl)-phosphinate, m.p. 65°-68°, 31P-NMR spectrum: δ=+44.9 ppm (CDCl3).
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