New Syntheses of Praziquantel: 2-(Cyclohexylcarbonyl)-1,2,3,6,7,11b-hexahydro-4H-pyrazino[2,1-a]isoquinolin-4-one

Abstract

This paper describes two d i f f e r e n t synthetic pathways f o r praziquantel, a new broad spectrum schistosomicide and cestocide.Easy t o apply on an i n d u s t r i a l scale, they involve a selective reduction o f 4-acyl-I-phenethylpiperazine-2.6-dionei n 4-acyl-6-hydroxy-1-phenethylpiperazin-2.one, the c y c l i s a t i o n o f which i n a c i d i c medium gives t r i c y c l i c compounds 2-acyl-1,2,3,6,7,llb-hexahydro-4H-pyrazin ~2,1-a_7isoquinolin-4-one.B i l h a r z i a s i s , a seri'ous p a r a s i t i c disease, very widespread i n many t r o p i c a l and subtropical coun-1 t r i e s o f Africa, China and B r a z i l , i n f e c t s more than 200 m i l l i o n people according t o WHO .2 Praziquantel (1). a well-known anticestodal compound exhibits remarkable a c t i v i t y a g a i n s t a l l