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A research focuses on a mechanistic study of the mechanism involved in an effective asymmetric hydrogenation and reduction of [alpha],[beta]-unsaturated carboxylic acid, which is usually catalyzed by several Ruthenium complexes having axially chiral ligands. The results show that protonolysis is the major pathway for metal-carbon cleavage under neutral conditions, where as the hydrogenolysis of metal-carbon bond predominates under the basic conditions.

A highly efficient strategy is developed for the rapid asymmetric synthesis of gem-dimethyl and spirocyclopropyl norbornyl carboxylic acids. The key transformation involved the unprecedented asymmetric Diels-Alder reaction of highly reaction beta,beta-cyclopropyl-alpha,beta-unsaturated N-acyloxazolidinoones with cyclopentadiene affording the adducts in high yield and de.

A general asymmetric synthesis of substituted cycloalkyl[b]indoles is accomplished. The use of trimethylphosphine (PMe3) and bis(2,2,2-trichloroethyl) azodicarboxylate (TCEAD) is found to have an effect on the Mitsunobu dehydrative alkylation.

The article explains the structure and the isolation of parnafungins, the antifungal natural products that inhibit mRNA polyadenylation. The fungal polyadenosine polymerase is shown to act as the biochemical target of these natural products.

The title complex, [ZrCl2(C4H8O)2(C14H14N)2]·0.5C7H8, was prepared in an unusual manner by utilizing [Mg{N(CH2Ph)2}2] as a ligand transfer reagent. The Zr atom lies in a distorted octahedral environment where steric repulsion from the large di­benzyl­amino ligands leads to a widening of the N-Zr-N angle [99.95 (9)°] and corresponding compression of other angles [Cl-Zr-Cl 160.95 (3)° and O-Zr-O 78.22 (7)°]. This distortion is compared with those found in the previously determined structures of the di­methyl­amino and diethyl­amino analogues. [ABSTRACT FROM AUTHOR]

Ruthenium complexes employing axially chiral ligands were found to be effective asymmetric hydrogenation catalysts for the reduction of α,β-unsaturated ene acid 1-E to give 2, a prostaglandin D2 (PGD2) receptor antagonist. With [(S-BINAP)Ru(ρ-cymene)CI2]2 (3, S-BINAP = (S)-(+)-2,2′-bis(diphenylphospino)-1,1′-binapthyl), it was discovered that low hydrogen pressures (<30 psi) were essential to achieve high enantioselectivities (92% ee). A detailed mechanistic study was undertaken to elucidate this pressure dependence. It was determined that compound 1-E is in a ruthenium-catalyzed equilibrium with endocylic isomer 1-Endo and in photochemical equilibrium with Z isomer 1-Z. Each isomer could be hydrogenated to give 2, albeit with different rates and enantioselectivities. Hydrogenation of 1-Endo with 3 was found to give 2 in high enantiomeric excess, regardless of pressure and at a rate substantially faster than that of hydrogenation of 1-1E and 1-Z. In contrast, isomers 1-E and 1-Z exhibited pressure-dependent enantioselectivities, with higher enantiomeric excesses obtained at lower pressures. A rationale for this pressure dependence is described. Deuterium labeling studies with 1-Endo and tiglic acid were used to elucidate the mechanism of hydride insertion and product release from ruthenium. Under neutral conditions, protonolysis was the major pathway for metal-carbon cleavage, while under basic conditions, hydrogenolysis of the metal-carbon bond was predominant. [ABSTRACT FROM AUTHOR]

A general asymmetric synthesis of substituted cycloalkyl[b]indoles has been accomplished. The key features of this approach are (1) the utilization of a Japp-Klingemann condensation/Fischer cyclization to prepare cycloalkyl[b]indolones, (2) the asymmetric borane reduction of these heterocyclic ketones with (S)-OAB to obtain enantiomerically pure alcohols, and (3) the stereoselective S(N)2-displacement of these indole alcohol substrates with a carbon nucleophile under Mitsunobu conditions to set the C1 or C3 tertiary carbon stereocenter. The use of trimethylphosphine (PMe3) and bis(2,2,2-trichloroethyl) azodicarboxylate (TCEAD) was found to have an effect on the Mitsunobu dehydrative alkylation.