Scheme 16: Proposed mode of formation of the cyclitol moiety of pyralomicins. 77: 2-epi-5-epi-valiolone; 102: 2-epi-5-epi-valiolone-7-phosphate; 107: 5-epi-valiolone-7-phosphate; 103: valienone-7-phosphate; 108: valienol-7-phosphate; 109: valienol-1-phosphate; 110: NDP-valienol.