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O n e -P o t R e a r r a n g e m e n t o f C a r b o x y l i c A c i d s t o C a r b a m a t e s Abstract: A simple one-pot conversion of carboxylic acids to carbamates is achieved by propylphosphonic anhydride (T3P ® ) in combination with azidotrimethylsilane and an alcohol via the Curtius rearrangement. Besides diverse primary to tertiary alcohols, the reaction tolerated a wide scope of aromatic, heterocyclic, and aliphatic carboxylic acids which underwent rearrangement in excellent yields.

The objective of the present study was to develop mucoadhesive microspheres of captopril in order to achieve extended retention in upper gastro intestinal tract to enhance absorption and bioavailability. The microspheres were prepared by emulsification method using different ratio of sodium alginate with captopril by cross-linking with calcium chloride. Fourier-transform infrared spectroscopy study shows that captopril and other excipients are compatible with each other. The effects of polymers concentration on drug release profile were investigated. Response surface methodology was applied to systemically optimize the drug release profile. Polymer to drug ratio and stirring speed were selected as independent variables. Drug entrapment efficiency, percentage mucoadhesive and in vitro drug release after 6 hours were selected as dependent variables. Obtained microspheres were subjected to different evaluation parameters such as percentage yield, particle size analysis, drug entrapment efficiency, percentage mucoadhesive, in vitro drug release, drug release kinetics and scanning electron microscopy. The optimized formulation (MM10) showed satisfactory drug entrapment efficiency of 80.34±1.8 %, percentage mucoadhesive of 95.75±1.2 and percentage drug release after 6 hours of 26.08±0.45 %. Scanning electron microscopy analysis revealed that particles were spherical with smooth surface. Particles were free flowing with average particle size of 51.43 μm. Better results were observed from optimized mucoadhesive microspheres of captopril, thereby improving the bioavailability due to prolong release of drug in stomach.

Carbamates. -T3P as condensing agent in combination with trimethylsilylazide and triethylamine provides a practical method for the direct conversion of a broad range of carboxylic acids and alcohols to carbamates. -(AUGUSTINE*, J. K.; BOMBRUN, A.; MANDAL, A. B.; ALAGARSAMY, P.; ATTA, R. N.; SELVAM, P.; Synthesis 2011, 9, 1477-1483, http://dx.