In order to obtain antischistosomal agents by modification of the chemical structure of praziquantel

five compounds of 2-substituted dithioformic acid ester of 1

2

3

6

7

11b-hexahydro-4H-pyrazine [2

1-a] isoquinolinones Were synthesized.Screening with experimental

compound VIa

c and e showed lower activity against schistosomiasis japonicum in mice than praziquantel.2-Benzoyl-1

2

3

6

7

11b-hexahydro-4H-pyrazine [2

1-a] iscquinolin-4-ones

a key intermediate for the synthesis of praziquantel analogues

was prepared by utilizing phase transfer catalysis techniques in 86% yield from 1-benzoylaminomethyl- -chloroacetyl-1

2

3

4-tetrahydro-isoquinolin