III (6.0 g, 0.0148 mole) (39) was deblocked with HCl/Dioxane and solvent removed under reduced pressure. The residue was triturated with ether, filtered, washed with ether, then pet. ether and dried. A very hygroscopic material was obtained (4.2 g, 0.0123 mole) which was coupled in DMF with II (2.86 g, 0.0123 mole) in the presence of 10% excess of EDCI (2.60 g) and HOBt (2.07 g). The reaction was worked up as described for I to obtain IV as a white foam in a quantitative yield, no sharp m.p. 54°-62° C. Rf2, 0.42; Rf3, 0.74. Anal. Calcd. for C26H38N4O7 ; C, 60.21; H, 7.38; N, 10.80%. Found: C, 60.0; H, 7.46; N, 10.81%.
