Mechanisms and transition states of 1,3-dipolar cycloadditions of phenyl azide with enamines: a computational analysis.

The transition structures for the 1,3-dipolar cycloadditions of phenyl azide to enamines derived from acetophenone or phenylacetaldehyde and piperidine, morpholine, or pyrrolidine were located using quantum mechanical methods. These cycloadditions were studied experimentally in 1975 by Meilahn, Cox, and Munk (J. Org. Chem. 1975, 40, 819-823). Calculations were carried out with M06-2X/6-311+G(d,p), SCS-MP2/6-311+G(d,p)//M06-2X/6-311+G(d,p), and B97D/6-311+G(d,p) methods with the IEF-PCM solvation model for chloroform and ethanol. The distortion/interaction model was utilized to understand mechanisms, reactivities, and selectivities.

INFERCNMR: a 13C NMR interpretive library search system.

INFERCNMR is an automated (13)C NMR spectrum interpretation aid for use either as a stand-alone program or as a component of a comprehensive, computer-based system for the characterization of chemical structure. The program is an interpretive library search which requires a database of assigned (13)C NMR spectra. An interpretive library search does not require overall structural similarity between an unknown and a library entry in order to retrieve a substructure common to both. Input consists of the chemical shift and one-bond proton-carbon multiplicity of each signal in the spectrum, and the molecular formula of the unknown. Program output is one or more substructures predicted to be present in the unknown, each of which is assigned an estimated prediction accuracy.

Bhimamycin A to approximately E and bhimanone: isolation, structure elucidation and biological activity of novel quinone antibiotics from a terrestrial Streptomycete.

From the ethyl acetate extract of a terrestrial Streptomycete isolate, five new quinone antibiotics, bhimamycin A (2a), B (2b), C (3c), D (5a), E (7) and the new tetralone bhimanone (8) were isolated together with the known microbial products chrysophanol (1a), aloesaponarin II (1b), 3,8-dihydroxy-1-methylanthraquinone-2-carboxylic acid (1c), adenosine, 2'-deoxyadenosine, phenylacetamide, and 2-(p-hydroxyphenyl)ethanol. The structures of these natural products were deduced from the spectral data and confirmed by comparison with related compounds from the literature and by synthesis.