The 8aR absolute stereochemistry of Wieland-Miescher ketone (-)-I was established by the X-ray structure analysis of its bis(4-bromobenzoate) derivatives (1R,6R,8aR)-(+)-IV and (1R,6S,8aR)-(-)-V. The absolute configuration of (-)-I was corroborated further by the application of the CD exciton chirality method to bis(4-bromobenzoates) (+)-IV and (-)-V.
Racemates of (η3-allyl)tricarbonyliron lactone complex Fe(CO)3{η1:η3-C(O)XCH2CHCMeCH2} 1a (X = O) and (η3-allyl)tricarbonyliron lactam complex 2a (X = NMe) are resolved on a preparative scale by HPLC on cellulose tris(3,5-dimethylphenyl)carbamate/silica gel RP-8 and the absolute configuration of (-)-2a is determined by X-ray crystal structure analysis.
The 1H and 13C NMR spectral assignments of ethyl 2-aroyl-4,5-dimethyl-1,2,3,6-tetrahydropyridazine-1-carboxylates (1a-1h) and ethyl 2-arylcarbamoyl-4,5-dimethyl-1,2,3,6-tetrahydropyridazine-1-carboxylates (2a-2k) are given based on DQF COSY, 1H,13C HMQC and 1H,13C HMBC-measurements; the dynamics of the tetrahydropyridazine ring has been studied by 1H, 1H EXSY-technique and the structure of one congener (4′-methylphenyl-derivative, 2a) has been confirmed by X-ray structure analysis.
Crystal Structures of the Catalytic Domain of Arabidopsis thaliana Starch Synthase IV, of Granule Bound Starch Synthase From CLg1 and of Granule Bound Starch Synthase I of Cyanophora paradoxa Illustrate Substrate Recognition in Starch Synthases