| abstract |
A compound of the formula :n wherein nR¹ and R² are each lower alkyl, nR³ is hydroxy or acyloxy and R⁴ is hydrogen, or nR³ and R⁴ are linked together to form a bond, nR⁵ is hydrogen or lower alkyl and R⁶ is hydrogen, lower alkyl or aryl, or nR⁵ and R⁶ are linked together to form lower alkylene, nR⁷ is cyano, acyl, halogen, nitro or lower alkyl, nX is cyanoiminomethylene or sulfonyl, and nY is single bond, thio, imino which may have lower alkyl, nwith certain provisions, pharmaceutically acceptable salts thereof, processes for their preparation, and pharmaceutical compositions comprising them as an active ingredient. |