NEW MATERIAL:A derivative of formula I (R1 and R2 are H, lower alkyl, haloalkyl, hydroxyalkyl, cycloalkyl, etc.; A is straight or branched chain alkylene which may be substituted by aryl; R3 is lower alkyl, haloalkyl, lower alkenyl, lower alkynyl, etc.).
EXAMPLE: Methyl 4-carbamoyloxytetrolate.
USE: An intermediate for preparing medicines, useful for treating cardiovascular diseases, and useful as an intermediate for preparing 2-carbamoyloxyalkyl-1,4- dihydropyridine derivatives having calcium antagonistic, vasodilator and hypotensive action.
PROCESS: An acetylenic compound of formula II is reacted with an isocyanate of the formula R6NCO (R6 is chlorosulfonyl, dichlorophosphoryl or H, etc.) or a compound capable of producing the compound under the reaction conditions, etc. to afford the aimed compound of formula I .
SUZUKI KUNIO
USHIJIMA RIYOUSUKE
NAKAGAWA SUSUMU
