Selective Monocarbamoylation of Symmetrical Diols with Alkyl Halides and Potassium Cyanate Using Phase-Transfer Catalysis
作者:Mahavir Prashad、John C. Tomesch、William J. Houlihan
DOI:10.1055/s-1990-26910
日期:——
A convenient method for the selective monocarbamoylation of diols by reaction with alkyl isocyanates, generated in situ from alkyl halides and potassium cyanate under phase-transfer catalysis, is described. Under these conditions the ease of reaction shows the following order cis-diols > trans-diols and diols > monoalcohols. An increase in the number of methylene groups between two hydroxyl groups lead to a decrease in product yields. A plausible mechanism to explain these results is proposed.
New platelet activating factor (PAF) antagonists, 3 were synthesized by replacing the charged phosphate and trimethylammonium moieties with sulfonamide and heterocyclic quarternary ammonium functionalities, respectively(PAF-sulfonamide isosteres). Darmstoff phosphatidic acid analogues of this class (Darmstoff-sulfonamide isosteres), 6 were also synthesized.The activity of these compounds as PAF antagonists was evaluated from their in vitro inhibitory effect on PAF-induced platelet aggregation in rabbit platelet-rich plasma. Among the compounds tested, some of the 2-methoxypropane derivatives with an octadecylcarbamoyloxy or octadecylcarbamoylthio side chain at the 1-position and a propylsulfonamide function bearing a terminal polar substituent such as a quarternary quinolinium or substituted quinolinium group at the 3-position were found to be the most potent (IC50=0.3-0.6μM).