Structure of 3-O-acetylgibberellin A3.

C21H24O7, Mr = 388.4, orthorhombic, P2(1)2(1)2(1), a = 13.279 (10), b = 15.615 (10), c = 9.427 (8) A, V = 1954.7 A3, Z = 4, D chi = 1.319 g cm-3, lambda(Mo K alpha) = 0.71069 A, mu = 1.0 cm-1, F(000) = 824, T = 293 K, R = 0.049 for 1805 observed reflections. The gibberellane skeleton shows the conformational variety characteristic of many other gibberellin derivatives. Ring A is in a sofa conformation while the five-membered ring B assumes an intermediate conformation between an envelope and a half-chair. The lactone ring is in an ideal envelope conformation and shows a marked difference in its two C-O distances. Each molecule is hydrogen bonded to two others to form continuous spiral chains along the c axis.