Structure and stereochemical assignment of spheropsidone, a phytotoxin from Diplodia cupressi

Sphaeropsidone is a phytotoxin produced in very large amt. by Diplodia cupressi. It crystallizes in the monoclinic P21 space group with two mols. in the asym. unit. Cell parameters are: a = 4.1280(6) Å, b = 13.161(1) Å, c = 13.333(3) Å, β = 90.14(1)°, Z = 4, D calc = 1.432 mg/m3 at 173 K. The final refinement converged to R 1 = 0.0413, wR 2 = 0.0730 for 1684 obsd. reflections. In sphaeropsidone, the hydroxyl group and oxirane oxygen atoms are mutually cis positioned. The abs. stereochem. at the three chiral centers turns out to be 1S,5R,6S. The stereochem. assignment of spaeropsidone is a fundamental basis for the assignment of the abs. configuration of some of its derivs. used in structure-activity relationship studies. No intramol. hydrogen bonds are found. In the crystal packing, the hydroxyl and carbonyl oxygen atoms are involved in head-to-tail intermol. hydrogen bonds to form infinite linear chains of mols. running along c. The linear chains are arranged into layers of mols. stacked along a.