Avermectin → Ivermectin B1a

참여 물질

반응 조건

반응 단계

39 g of Avermectin Bla is dissolved in 1540 ml of toluene and introduced into a 4 liter stirred autoclave. To this is added 3.9 g of tris(triphenylphosphine)rhodium (I) chloride (Wilkinson's catalyst). A hydrogenation pressure of 40 psi and a temperature of 40° C. is maintained with stirring for 41/2 hours. At the end of this period liquid chromatographic analysis indicates 98% yield of dihydro avermectin Bla with 1.5% of tetrahydro avermectin Bla. The toluene is removed by evaporation in vacuo and the dark red gum is dissolved in ethanol at a rate of 4 ml of ethanol per gram of product. Formamide at a rate of 10 ml per gram of product is added and the solution heated on the steam bath to 40°-50° while adding water at a rate of 2 ml per gram of product. After crystallization commences the heat is removed and the solution allowed to cool slowly with stirring overnight. The solid is filtered off and washed with a mixture 3 parts water and 1 part ethanol and dried in vacuo overnight. The solids are dissolved in 150 ml of ethanol and warmed to 35°-40° C. on the steam bath. Water, 150 ml is added slowly with stirring. When solution is complete at 35° C. the heat is removed and the solution allowed to cool slowly overnight. The crystals are removed by filtration and washed with aqueous ethanol and dried in vacuo overnight affording 32.55 g of 22,23-dihydro avermectin Bla with a m.p. of 155°-157° C.

출처 및 근거