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Abstract
A mechanochemical procedure of ball milling was applied to a solvent-free synthesis of natural alkaloid lappaconitine derivatives. A mixture of purely solid lappaconitine and 3-Cl-perbenzoic acid reacted to give lappaconitine N(20)-oxide with a good isolated yield (57percnt after workup). The ball milling of solid lappaconitine and N-bromosuccinimide affords N(20)-deethyllappaconitine with an acceptable (42percnt) yield. The mechanochemical approach was also applied for acylation of the anti-inflammatory drug piroxicam to improve its therapeutical properties. Consequently piroxicam 4-nitrobenzoate was obtained under the solvent-free reaction conditions with a moderate yield as a result of mechanical activation of the reaction between piroxicam and 4-nitrobenzoyl chloride in the presence of the aluminum oxide impregnated with thriethylamine. The reaction mixtures were analyzed after ball milling by HPLC in the proposed conditions.
ACKNOWLEDGMENTS
We thank Dr. Nikolay Gorobets for valuable discussion of the work results. The financial support of this study from the U.S. Civilian Research & Development Foundation, CRDF (Award No. RUX0-008-NO-X1) is gratefully acknowledged. The work was also supported by Russian Ministry of Education and Science, Russian Foundation for Basic Research (No. 05-03-08029), and the RAS Program “Fundamental Science for Medicine.”