Conformation of uncomplexed natural antamanide crystallized from CH(3)CN/H(2)O.

Natural antamanide, a cyclic decapeptide from Amanita phalloides, has been shown to have the same conformation for the backbone and comparable side groups as the biologically active synthetic [Phe(4), Val(6)]antamanide. Packing in the crystal is quite different for the two compounds. Large channels with a polar lining are formed in the crystals of [Phe(4), Val(6)]antamanide, whereas in natural antamanide large channels in the crystal are completely surrounded by the lipophilic side groups of the Pro, Phe, and Ala residues. Antamanide, C(64)H(78)N(10)O(10).8H(2)O.X, crystallizes in space group P2(1)2(1)2(1) with a = 15.88 A, b = 34.88 A, and c = 13.61 A.