Novel conditions for the transformation of gem‐dibromomethylenes to ketones are described. gem‐Dibromo compounds were treated with acetic anhydride and triethylamine in dichloromethane/water at room temperature under an air atmosphere to give the corresponding ketones in moderate yields. A radical mechanism is proposed based on experimental results.
Synthesis of both enantiomers of crambescin B carboxylic acid is described. A cis-enyne starting material was epoxidized under the conditions of Katsuki asymmetric epoxidation to give 95% ee of the epoxide, which was transformed to crambescin B carboxylic acid via bromocation-triggered cascade cyclization as the key step. Enantiomerically pure crambescin A and C carboxylic acids were also synthesized
mutants, at the isolated gp right atrium, and in GTPase assays for activity on recombinantH1, H3, and H4 receptors. The bivalent ligands are H2R partial or full agonists, up to 2 orders of magnitude more potent than monovalent acylguanidines and, with octanedioyl or decanedioyl spacers, up to 4000 times more potent than histamine at the gpH2R. In contrast to their imidazole analogues, the aminothiazoles
A Nitrone Dipolar Cycloaddition Strategy toward an Enantioselective Synthesis of Massadine
作者:Jeffrey S. Cannon
DOI:10.1021/acs.orglett.8b01464
日期:2018.7.6
of the massadine D-ring by a synthetic route that features a diastereoselective and stereospecific Ireland–Claisen rearrangement of a trianionic enolate followed by a diastereoselective nitrone dipolar cycloaddition of a highly electron-poor oxime.
Bromocyclization of Alkynyl Guanidine: A New Approach to the Synthesis of Cyclic Guanidines of Saxitoxin
作者:Toshio Nishikawa、Yusuke Sawayama
DOI:10.1055/s-0030-1259546
日期:2011.3
Bromocyclization of propargyl and homopropargyl guanidines possessing homopropargyl alcohol provides five- and six-membered cyclicguanidines with spiro-hemiaminal, respectively, a candidate of precursors for saxitoxin.