Acknowledgment. GHP acknowledges financial support from the National Science Foundation (Grant No. CHE 79-15161), and JC acknowledges financial support from the National Institutes of Health (Grant No. CA- 24487). ... Registry No. (2S,3S)-la, 75917-46-3; (2R,3S)-lb, 75917-45-2; (S)-2,74036-33-2; (S)-5,79681-26-8; 6,79681-27-9; 7a, 79681-28-0; 7b, 79732-89-1; vinyl bromide, 593-60-2. ... Supplementary Material Available: Experimental ...