Crystal and molecular structure of a new Z-DNA crystal form: d[CGT(2-NH2-A)CG] and its platinated derivative.

The three-dimensional structure of d[CGTA'CG], where A' = [2-NH2-A], was determined to atomic (1.35 A) resolution by single isomorphous replacement. The d[CGTA'CG] hexamer crystallizes in space group P3221, and is not isomorphous with other DNA hexanucleotides.

9,11-Secogorgost-5-en-9-one-3 beta,11-diol, a marine steroid from the sea whip Pseudopterogorgia hummelinkii.

The title steroid [(22R,23R,24R)-22,23-methylene-23,24-dimethyl-9,11- secocholest-5-en-9-one-3 beta,11-diol, C30H50O3], was isolated from Pseudopterogorgia hummelinkii, a Caribbean gorgonian. The cyclopropane ring in the side chain of this molecule, a feature very unusual in terrestrial steroids, has been found in several other marine steroids. The molecular structure is potentially very flexible because of the oxidative cleavage of ring C, but the two independent molecules in the crystal have quite similar overall conformations.

Approaches to isozyme-specific inhibitors. 16. A novel methyl-C5' covalent adduct of L-ethionine and beta,gamma-imido-ATP as a potent multisubstrate inhibitor of rat methionine adenosyltransferases.

N6,N6-Dibenzoyl-2',3'-O-isopropylideneadenosine, which is readily synthesized by one-pot 5'-O-trimethylsilylation, N6-benzoylation, and desilylation, was converted to the corresponding 5'-aldehyde. This was treated with CH2 = CHMgBr to afford, after debenzoylation, a 1:3 mixture of the 5'S and 5'R epimers, respectively, of 5'-C-vinyl-2',3'-O-isopropylideneadenosine. The configurations were established by single-crystal X-ray diffraction analysis of the 5'R epimer.