A synthesis of substituted phenylvaleric acids 4 a-e from 1,3-benzdioxolaldehyds 1a -d is described. Treatment with PPA gave benzocycloheptanones 5a-e which gave by reduction and dehydratisation benzocycloheptene 7 a-d. Reactions of benzocycloheptanone 5a and of benzocycloheptenaldehyds 10a-b are reported.