Seasoning materials chemistry by using a well-matured organic concept.

The concept "introduction of allylic 1,3-strain (A(1,3)-strain) to photochromism" originated from the experience of total synthesis of natural products about 18 years ago, when the author was a post doc. It was first applied to synthetic organic reactions, then it was successfully employed in the diastereoselective photochromic reactions of diarylethenes. A diastereomeric excess of the photoreaction was 88 % for the first example, and it was improved to 94 % by the recent operation of rational molecular tailoring.