Silicon-type cinnamic acid derivatives, method for their preparation, UV absorber and external skin treatment agent

摘要

A silicone type cinnamic acid derivative which is a siloxane having at least one unit represented by the formula (I): CHEM and having the other units which may exist in the siloxane being represented by the formula: O(4-m)/2SiR3m wherein R1 represents an alkyl group having 1 to 4 carbon atoms, a phenyl group, or a trimethylsiloxy group, R2 is a divalent hydrocarbon group having at least two carbon atoms, which may include a heteroatom O, X is an alkoxy group, n is an integer of 0 to 3, a is an integer of 2 or 3, R3 is an alkyl group having 1 to 4 carbon atoms, a phenyl group, or a trimethylsiloxy group, and m is an integer of 0 to 3.