Crystallization of Arthrobacter sp. strain 1C N-(1-D-carboxyethyl)-L-norvaline dehydrogenase and its complex with NAD+

The novel NAD+-linked opine dehydrogenase from a soil isolate Arthrobacter sp. strain 1C belongs to an enzyme superfamily whose members exhibit quite diverse substrate specificites. Crystals of this opine dehydrogenase, obtained in the presence or absence of co-factor and substrates, have been shown to diffract to beyond 1.8 ? resolution. X-ray precession photographs have established that the crystals belong to space group P21212, with cell parameters a = 104.9, b = 80.0, c = 45.5 ? and a single subunit in the asymmetric unit. The elucidation of the three-dimensional structure of this enzyme will provide a structural framework for this novel class of dehydrogenases to enable a comparison to be made with other enzyme families and also as the basis for mutagenesis experiments directed towards the production of natural and synthetic opine-type compounds containing two chiral centres.     

Synthesis of substituted quinolines using the dianion addition of N-Boc-anilines and alpha-tolylsulfonyl-alpha,beta-unsaturated ketones

A short and versatile synthesis of substituted quinolines is provided. Alkylation of sodium tolylsulfinate with bromomethyl- or chloromethyl ketones generates beta-keto sulfones. Knoevenagel condensation of the beta-keto sulfones with an aldehyde provides alpha-tolylsulfonyl-alpha,beta-unsaturated ketones. Michael addition of the dianion of N-Boc-anilines in the presence of CuCN and LiCl with the unsaturated ketone generates a 1,4-adduct, which after deprotection of the Boc group and thermal elimination of the tolyl sulfone provides the quinoline.     

Solid-phase synthesis of macrolide analogues

The synthesis of a solid-phase macrolide library is described. The library introduces three sites of diversity to a suitable macrolide scaffold via reductive aminations.     

Synthesis of 2-substituted (+/-)-(2r,3r,5r)-tetrahydrofuran-3,5-dicarboxylic acid derivatives

An efficient synthesis of 2-substituted (+/-)-(2R,3R,5R)-tetrahydrofuran-3,5-dicarboxylic acid derivatives has been developed. Starting from 5-norborne-2-ol, the key intermediate (+/-)-methyl 5,6-exo,exo-(isopropylidenedioxy)-2-oxabicyclo[2.2.1]heptane-3-exo-carboxylate (15) was synthesized in an efficient six-step sequence. The key transformation is the base-catalyzed methanolysis-rearrangement of (+/-)-6,7-exo,exo-(isopropylidenedioxy)-4-exo-iodo-2-oxabicyclo[3.2.1]octan-3-one (14). Further manipulation of the 3-substituent of (+/-)-methyl 5,6-exo,exo-(isopropylidenedioxy)-2-oxabicyclo[2.2.1]heptane-3-exo-carboxylate (15) followed by deprotection of the diol moiety and ring opening catalyzed by RuCl(3)/NaIO(4) gave the title compounds in good yield.     

A Novel and Expeditious Route to A-81988: An Angiotensin II Receptor Antagonist

A novel and efficient synthesis of A-81988, an angiotensin II receptor antagonist, is described. The key step utilizes a palladium-catalyzed biaryl coupling between a phenylboronic acid derivative and N-trityl-5-(2-bromophenyl)tetrazole.     

A facile synthesis of antitumoral indeno[1,2-c]pyrazole-4-one by mild oxidation with molecular oxygen

An efficient, convenient, and general synthetic method for indeno[1,2-c]pyrazole-4-ones through oxidation of indenopyrazoles by treatment with a base and molecular oxygen is described, and a possible mechanism for the oxidation is proposed. The product indeno[1,2-c]pyrazole-4-ones were elaborated further by Suzuki coupling and Mitsunobu reaction.     

Computer application to vibronic spectra including dd transitions

The previously described (refs 1, 2) computer method for resolution of the vibronic spectra was improved by using the regression analysis of the progression member intensities. The method was applied to the experimental spectra of uranyl nitrate in organic solvents for three strongly overlapping progressions and to the simulated theoretical spectra consisting of a set of dd and vibronic bands.     

Application of base cleavable safety catch linkers to solid phase library production

We have used sulfide "Safety Catch" linkers to anchor typical medicinal chemistry functional groups to amine resins. Compounds are loaded as the ester, carbamate, or amine. At the end of the synthesis, the linker is activated by peracid. The sulfone resins are then cleaved by beta-elimination in the gas phase or in solution by secondary amines to produce acids and primary, secondary, or tertiary amines. Comparison of cleavage rates to other sulfone resins including SEM showed significantly faster cleavage for this system with conditions similar to Fmoc deprotection. Application of this strategy to a medicinal chemistry library gives good yields and purities of the resulting compounds.