NEW MATERIAL: The compound of formula I [R1 is lower alkoxy or phenyl substituted with halogen; R2 is OH, lower alkoxy, lower alkanoyloxy, lower cycloalkylcarbonyloxy; R3 and R4 are each lower alkyl, phenyl lower alkyl or together form a piperidine or pyrrolodine ring; (n) is 2 to 4; (m) is 1 or 2] or its acid addition salt.

EXAMPLE: (±)-Cis-2,3-dihydro-3-hydroxy-5-[2-(dimethylamino) ethyl]-2-(4- methoxyphenyl) naphtho[2,1-6][1,4]thiazepine-4(5H)-one.

USE: Medicaments. Having activity as calcium channel blockers and accordingly, being useful as agents for treatment of ischemia and blood pressure lowering.

PROCESS: The compound of formula I when R2 is OH is obtained by allowing the compound of formula II to react with the compound of formula III (Z is halogen).