A Ca(OTf) 2 -and self-promoted ynone−amidine atom-economic formal [4 + 2]-cycloaddition of various ynones with amidines is reported for the construction of highly functionalized tricyclic azepines. High reaction rate, ease of operation, and high product selectivity with wide substrate scope are the key advantages of the present annulation protocol.
Bioactive compounds featuring an unusual core of spiro[5.5]undecenes and calliviminones were synthesized in very good yield with good regio-and diastereoselectivities through a one-pot Knoevenagel and [4 + 2] cycloaddition from the readily available aldehydes, cyclic-1,3-diones, dienes, and a catalytic amount of (S)-proline.
Biologically important 4-alkylsyncarpic
acids, which resemble the
core structure of many natural products, were synthesized in one-pot
through the organocatalytic three-component reductive alkylation with
excellent yields and C-selectivity. Synthetic applications
of 4-alkylsyncarpic acids were demonstrated by converting into the
functionally rich molecules through different reactions like Michael, retro-Michael, reduction, and oxidation reactions. In a
continuation, formal total synthesis of (±)-triumphalone, (±)-isotriumphalone,
and monomeric phloroglucinol derivatives was reported in a few steps
starting from 4-alkylsyncarpic acids in overall very good yields.
Further showcasing the importance of C-alkylated
products, 4-benzylsyncarpic acid and its Michael adduct with methyl
vinyl ketone were synthesized in a gram scale without compromising
rate/yields.
The crystal structure of the SIV matrix antigen (MA) has been determined at lOOK (to dmin 2.LK,.) and 293K (to dmin 2.2A) by multiple isomorphous replacement and cross-averaging l. The refined models (R-factors 18.0% and 16.4% for the lOOK and 293K structures respectively) m-e highly similar (r.m.s deviation 0.18A between Ca atoms) but in some places the electron density is better defined for the 1 OOK structure.MA has roles delineated in tm-getting Pr55 Gag to the plasma membrane, facilitating incorporation of the virus envelope glycoprotein (portions of which also form trimers2) and assembly of the Pr55 Gag shell. The structure revealed that when forced into a higher order assembly in the crystal, the MA subunits form a trimer. This oligomer may correspond to a basic building block in the Gag shell, explaining many of the biological properties of the protein . It has since been conoborated by a crystallographic analysis of its HIV homologue3 (50% sequence identity).The three-dimensional structure also suggests a model for retroviral Gag shell assembly. These implications and future possibilities for inhibitor design will be discussedWe will describe our progress towar-d a structure determination for cores of reovirus. Reovirus consists of a segmented ds RNA genome smTounded by two concentric protein shells. Wl1en the outer shell of reovirus is proteolytically removed, the viral core becomes active as a RNA processing machine.
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