Die Erfindung betrifft ein neues Verfahren zur Hydroxymethylierung von nichtzyklischen α,α-Dialkyl-Carbonsäurederivaten mit Formaldehyd unter Verwendung von Amid-Basen bei Temperaturen von -40°C bis zum Siedepunkt des verwendeten Lösungsmittels oder Lösungsmittelgemisches.

Cyclooctadiene derivative of the following formula (1): wherein A¹, A², A³ and A⁴ each independently represent COOR⁵ (where R⁵ represents a hydrogen atom, a C₁-C₁₀ alkyl group, a phenyl group, a C₇-C₁₂ aralkyl group or CONR⁶R⁷ (where R⁶ and R⁷ each independently represent a hydrogen atom, a C₁-C₁₀ alkyl group or a phenyl group), or A¹ and A², and/or A³ and A⁴ may be combined together to represent group(s) of: in which X represents an oxygen atom or NR⁸ {where R⁸ represents a hydrogen atom, a C₁-C₁₀ alkyl group or a phenyl group),

R⁰, R¹ , R², R³ and R⁴ each independently represent a hydrogen atom, a halogen atom, a hydroxyl group and an C₁-C₁₀ alkyl group,

the symbol --- represents a single or double bond, and when it is a double bond, then R¹ and R³ each independently may represent an oxygen atom;

provided that the case where all of R⁰, R¹, R², R³ and R⁴ represent hydrogen atoms at the same time is excluded, and agrohorticultural fungicides, antimold agents and antithrombocytic agents containing said derivatives.

The compounds have superior fungicidal activity, antimold activity and activity for preventing platelet aggregation, and are useful as an agrohorticultural fungicide, an antimold agent and an antithrombocytic agent.