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Calcium tungstate was found to be an excellent catalyst for large scale “green” oxidations of organic substrates (amines, alkenes, alcohols, sulfides) with hydrogen peroxide. It displays the unusual dual characteristics of producing a soluble pertungstate species, allowing for homogeneous reaction conditions, but then precipitating, unchanged, at the end of the oxidation. These qualities allow for easy catalyst recovery and minimal waste stream generation for large scale application.

The design and synthesis of an environmentally sensitive long wavelength fluorescing squaraine dye for conjugation toproteins is described. Environmentally sensitive dyes are valuable for probing environmental changes that occur whenlabeled proteins bind their corresponding ligands and can be used to construct fluorescent sensors. Long wavelength(>650 nm) dyes would enable through-skin wireless sensing with minimum interference from the background. While

Oxidosqualene-lanosterol cyclase (OSLC) from sonicated baker’s yeast has been employed for the stereoselective synthesis of lanosterol and its analogs. An extensive study of the enzyme’s reactivity profile has been conducted using surrogate substrates displaying structural modifications at both termini of the squalene backbone. Additional probes for assessing the enzyme’s tolerance with respect to structural modification of the internal portion of the hydrocarbon system have also been investigated. The successful cyclization of such compounds has resulted in a biocatalytic synthesis of remote functionalized sterols. Furthermore, a tentative model for predicting the substrate flexibility for OSLC is presented. Work toward developing an enzymatic synthesis of the biologically important pregnane steroid system is discussed along with the progress toward developing a cyclase mediated route to the asymmetric synthesis of bicyclofarnesyl terpene ring systems. This latter approach rests on the ability of OSLC to cyclize modified farnesyl derivatives as a direct means for the stereoselective assembly of the bicyclic framework.

On cite divers procedes et on les applique a des nitriles secondaires portant des substituants dialkyles aryles et alkyles et diaryles

Utilisation de la levure Saccharomyces cerevisiae pour la synthese asymetrique de sterol a partir de squalene

Le rearrangement de dienols R 2 C(OH)CH=CHC(X)=CR 2 avec un substituant arylthio ou alkylthio non terminal, en presence de NiCl 2 conduit aux dienols R 2 C=CH-CH=C(X)-CR 2 (OH). L'application aux steroides permet une nouvelle synthese de l'hydroxy-25 cholesterol(20R) a partir de la pregnenolone

A much improved synthesis of the heretofore difficultly obtainable 2,6-diaminopyrazine (4) was afforded by the low-pressure catalytic hydrogenation (palladium on carbon) of 2,6-diazido-pyrazine (2); reaction of 2,6-dichloropyrazine (1) and sodium azide gave 2 in 84% yield. The outcome of the reduction was found to be solvent dependent: 1,2-dimethoxyethane containing aqueous ammonia gave 4 in 83% yield; 1,2-dimethoxyethane alone gave 5-aminotetrazolo[1,5-a]-pyrazine (3) in 26% yield. Additional alternative syntheses of 3 and 4 are described. A number of acyl and azo derivatives of 4 were prepared. Reactions of 2 with dimethyl acetylenedicarboxylate and ethyl acetate (base catalyzed) leading to vic-triazole derivatives are also described.

Alcohols can be easily transformed to their corresponding methylthiomethyl ethers under mild conditions by treatment with methyl sulfide and benzoyl peroxide in acetonitrile.

The hitherto unknown intramolecular cycloaddition reaction of azo dienophiles, as outlined in Scheme I below, is described.

A method for the preparation of symmetrically substituted 1,3-diynes, 1,3-dienes, and biphenyls based on the copper(I1) nitrate mediated coupling of organotin compounds 1 (R = alkynyl, alkenyl, aryl) is described. The addition of alkynylstannane la, lb , or IC (a, R = THPOCH,C=C; b, R = n-C4H9C=C: c, R = C,&C=C) to 1 equiv of C U ( N O , ) ~ . ~ H ~ O in T H F a t 23 "C afforded 1,d-diynes 2a-c in 85%, 60%, and 50% yield, respectively.

The hitherto unknown intramolecular cycloaddition reaction of azo dienophiles, as outlined in Scheme I below, is described.

A method for the preparation of symmetrically substituted 1,3-diynes, 1,3-dienes, and biphenyls based on the copper(I1) nitrate mediated coupling of organotin compounds 1 (R = alkynyl, alkenyl, aryl) is described. The addition of alkynylstannane la, lb , or IC (a, R = THPOCH,C=C; b, R = n-C4H9C=C: c, R = C,&C=C) to 1 equiv of C U ( N O , ) ~ . ~ H ~ O in T H F a t 23 "C afforded 1,d-diynes 2a-c in 85%, 60%, and 50% yield, respectively.

Cyclization of 2,6-diaminopyrazine to two new heterocyclic ring systems, 1,3,5,7,9b-pentaazaphenalene and 1,3,4,6,8,9b-hexaazaphenalene is reported.