... R. In Biogenesis of Antibiotic Substances; Vanek, Z., (18) Bu'lock, JD In Comprehensive Organic Chemistry; Barton, (19 ... to yield a yellow brown solid, which was then combined with the organic phase, dried ... 1H); 6.38 (s, 1H); 5.43 (dd, J = 2.7, 2.5 Hz, 1H); 4.78 (ddd, J = 7.2, 2.21 ...