... USA 1972,69,1800. 1977,42,2426. SOC. 1952, 74, 2894. C. 1969,16,2134. 0022-2623/91/1834- 1545$02.M)/0 Q 1991 American Chemical Society Page 2. 1546 Journal of Medicinal Chemistry, 1991, Vol. 34, No. 5 Scheme I Bellamy et al. Scheme I1 Scheme I11 ...