Monocyclic Precursors Research Articles

Heterocycles of Hypervalent Sulfur and Selenium: New Syntheses and Structures

AbstractThis article describes synthetic and structural studies of heterocycles based on hypervalent sulfur and selenium, in particular 1,6,6aλ4‐triheterapentalenes, their monocyclic precursors and related compounds. What may be termed classical 1,6,6aλ4‐triheterapentalenes conform to structure (1), in which Y = S, Se or Te and X and Z are O, S, Se or NR [1]. Many aza analogues of (1) are known in which one or more ring carbon atoms at positions 2, 3, 4 and 5 are replaced by nitrogen atoms. In the majority of known 1,6,6aλ4‐triheterapentalenes, Y = S. Relatively few analogues are known in which Y = Se, and still fewer are known in which Y = Te. Analogues in which X and/or Ze is Te or PR have not hitherto been prepared.

Synthesis of micrococcinic acid

The first synthesis of micrococcinic acid ( 2) is described. The five rings of 2 are assembled from monocyclic precursors using four palladium-catalyzed biaryl coupling reactions. The synthesis of micrococcinic acid ( 2) is described.

Convergent synthesis of the tetracyclic bcde structural fragment of retigeranic acid

A two-step synthesis was proposed for the tetracyclic triquinane bis-enone from two monocyclic precursors. The bis-enone obtained is a structural fragment of retigeranic acid.

Automatic assembly of framework structures. 1. Synthesis, stereochemistry, and cyclization of derivatives of ?,??-dihydroxy-?,??-dimethyl- and ?-methyl-??-ethylglutaric acids

1. The principle of the stereocontrolled assembly of framework structures was confirmed for the case of the synthesis of bicyclic compounds with high yields under mild conditions from derivatives of d,l-α,α′-dihydroxy-α,α′-dimethyl- and threo-α,α′-dihydroxy-α-methyl-α′-ethylglutaric acids. 2. The conformation of the five-membered heterocycles in the derivatives of d,l- and meso-α,α′-dihydroxy-α,α′-dimethylglutaric acid and threo- and erythro-α,α′-dihydroxy-α-methyl-α′-ethylglutaric acids was studied. For the former it was shown that the functional groups have the a,a orientation, which favors secondary cyclization. On this basis the general principle of conformational control during the assembly of bicyclic systems from the monocyclic precursors was formulated. In the derivatives of the meso and erythro series the conformation of the ring changes with increase in the size of the substituent from a-CN to e-COOH and e-COOR. 3. It was shown that the products previously described as biscyanohydrins of acetylacetone and propionylacetone have the iminolactone structure.

Conformationally restricted analogs of atriopeptin(103-125) amide

Conformationally restricted analogues of atriopeptin(103-125)amide were prepared by synthesizing novel bicyclic peptides in which a second disulfide bridge linking residues 108 and 117 was introduced. These syntheses were shown to proceed with no significant scrambling of the disulfide bonds and demonstrated that structurally defined bicyclic analogues of atrial peptides could be easily prepared. The conformationally restrained analogues described here were found to be biologically active with potencies (EC50s) ranging from 0.05 to 3 microM. In addition, these bicyclic peptides (and many of the monocyclic precursors) were found to bind selectively to a class of specific tissue binding sites that have not been shown to be associated with any known second messenger system (NVR binding sites). Since affinity for the receptor class linked to vasorelaxation was negatively affected by the conformational restrictions described here, binding of atrial peptides to this class of receptors appears to have more specific conformational requirements than does binding to the NVR sites.

Thia-analogues of tropane alkaloids. Synthesis of intermediates from monocyclic precursors.

Thia-analogues of tropane alkaloids. Synthesis of intermediates from monocyclic precursors.

Synthesis of potential ambra odorants: 5,5,9-trimethyldecalyl derivatives.

AbstractThe synthesis of racemic stereoisomeric compounds with the 5,5,9‐trimethyldecalin skeleton and an oxygen function at C(1), C(2), or C(3) is describedAlthough racemic decalins are described, only the enantiomer related to steroids is drawn. The projection of the decalins was chosen so as to place the angular methyl group above the plane of the molecule and the oxygen function at C(1), C(2) or C(3) on the left side, as represented by formula 1–6. The relative configuration of the substituents in decalins is designated by using the convention of the steroid series: β, meaning on the same side as the angular methyl group at C(9) and α, meaning on the side opposite from the angular methyl group. The prefix cis or trans refers to the fusion of the decalin ring system, not to the position of the substituents. . A novel general one‐step synthesis of 2‐decalones by means of acid catalyzed cyclization of acyclic or monocyclic precursors has been developed.