added dropwise at 80 u00b0 c to a solution of 9 50 g of methyl s 2 methoxycarbonylamino 3 phenyl propionate and 3 22 ml of bromochloromethane in 60 ml of tetrahydrofuran subsequently a further 2 14 ml of bromochloromethane were added and the mixture was again treated with 23 ml of hexyllithium solution a further 1 54 ml of bromochloromethane were added and the mixture was again treated with 7 7 ml of hexyllithium solution the solution was treated at 80 u00b0 c with 15 ml of 20 methanolic hydrochloric acid warmed to 22 u00b0 and diluted with 100 ml of water and 40 ml of tetrahydrofuran the phases were separated the organic phase was washed with saturated sodium chloride solution dried and concentrated the residue was recrystallized from 40 ml of ethyl acetate and 160 ml of hexane and the crystallizate was dried yielding 3 83 g 37 of pure methyl s 1 benzyl 3 chloro 2 oxo propyl carbamate m p 121 u00b0 122 u00b0 c ir kbr 3336s nh 1737s and 1686s c u2550 o 1535s amide ii c 15 4 ml of a 2 6 molar solution of hexyllithium in hexane were added dropwise at 80 u00b0 c to a solution of 9 50 g of methyl s 2 methoxycarbonylamino 3 phenyl propionate in 60.