A mixture of N-[N2 -[(1,1-dimethylethoxy)carbonyl]-N6-[(phenylmethoxy)-carbonyl]-(R)-6-[(methoxy)carbonyl]-L-lysyl]-D-alanine 4-nitrophenylmethyl ester (40a, Kolodziejczyk, et. al., Int. J. Pept. Prot. Res., 1992, 39, 382; 683 mg, 1.06 mmol), 4-- molecular sieves (2.15 g, crushed), THF (10.5 mL), and benzyl alcohol (11.0 mL, 105.6 mmol) is stirred for 30 min and then treated with titanium(IV) isopropoxide (82 μl, 0.27 meq). The resulting mixture is heated for 24 h at 85°-90° C. The solids are filtered through diatomaceous earth and the solvent removed. The excess benzyl alcohol is removed by distillation on a Kugelrohr apparatus (approx. 1000μ pressure, 50°-75° C.). The crude orange oil is chromatographed (2.5×31 cm column), gradient of 4:1-2:1 hexane/EtOAc) to provide 40b (633 mg, 88% yield): NMR δ 1.39 (d, J=7.2, 3 H), 1.43 (s, 9 H), 1.40-1.67 (m, 4 H), 1.84 (br s, 2 H), 4.07 (br s, 1 H), 4.40 (m, 1 H), 4.58 (apparent quintet, 1 H), 5.0 (br d, 1 H), 5.07-5.25 (m, 6 H), 5.43 (br d, J=7.9, 1 H), 6.68 (br d, 1 H), 7.33 (m); MS (HR-FAB) m/z 676.3232 (M+H, calcd. for C37H46N3O9, 676.3234).
