evaporation of the solvent gave the deprotected derivative as a gum 4 15 g rf 0 2 silica ethylacetate hexane 2 1 c the product from step b 4 15 g was dissolved in dichloromethane 60 ml at 0 u00b0 c and a solution of triethylamine 0 68 g in dichloromethane 10 ml added followed by a solution of ethyl 2 trifluoromethanesulphonyloxy 4 phenyl butyrate 2 3 g in dichloromethane 10 ml the solution was allowed to warm to room temperature and was stirred at room temperature for 3 days the reaction mixture was diluted with dichloromethane 150 ml washed with 1n hydrochloric acid 3 u00d7 40 ml aqueous sodium bicarbonate 3 u00d7 40 ml brine 2 u00d7 40 ml and dried over magnesium sulphate the solution was filtered and evaporated to yield a gum which was chromatographed on silica eluting with a mixture of hexane and ethyl acetate the relevant fractions were combined and evaporated to yield 1 n 1 r s ethoxycarbonyl 3 phenylpropyl n 6 benzyloxycarbonyl s lysyl 2 r s benzyloxycarbonyl 6 2 2 2 trichloroethoxycarbonyl octahydro 6 azaindole 3 75 g as a gum d the product from step c 4 6 g was dissolved in glacial acetic acid 150 ml and treated with zinc dust 4 6 g following the procedure of example 41 to yield the title product as a yellowish gum 3 4 g rf 0 71 silica methyl isobutyl ketone saturated with 50 aqueous acetic acid a ethyl 2 bromo 4 phenylbutyrate 9 17 g in acetonitrile 50 ml was added to a stirred mixture of l leucine t butyl ester.