u00b0 c for 48 hours after filtration of the dicyclohexylurea the solvent was removed in vacuo the residue was dissolved in ch 2 cl 2 50 ml and sequentially washed with cold aqueous hcl 10 water aqueous nahco 3 10 and brine the organic phase was dried na 2 so 4 removal of solvent in vacuo gave a thick viscous residue which was flash chromatographed sio 2 eluting first with etoac ch 2 cl 2 1 1 then with 5 meoh in etoac furnished a 61 yield of the ester as a white solid 970 mg mp 115 118 u00b0 c 1 h nmr u03b4 1 42 s ch 3 81 h 1 64 2 20 m ch ch 2 63 h 5 58 bs nh 4h 13 c nmr u03b4 27 9 ch 3 28 4 u03b3 ch 29 6 30 0 nhcch 2 ch 2 coo 31 6 32 2 nhcch 2 ch 2 conh 36 6 u03b3 ch 2 39 2 u03b2 ch 2 41 1 u03b1 c 57 0 nhcch 2 ch 2 coo 57 6 nhcch 2 ch 2 conh 80 3 cch 3 172 6 coo 177 0 conh ir kbr 3348 2936 2850 1740 1665 1260 1040 cm u2212 1 anal calcd for c 87 h 148 o 22 n 4 c 65 22 h 9 31 n 3 50 found c 65 41 h 9 30.