Abscisic acid and its relatives—synthesis of optically active compounds

4 Abscisic acid and its relatives—synthesis of optically active compounds 2.1.4.1 Stereochemical problems on abscisic acid 

Because naturally occurring (+)-abscisic acid (27) did not give crystals good enough for X-ray crystallographic analysis, it was rather difficult to determine its absolute configuration. 

Almost at the same time Harada reported the S -configuration of (+)-abscisic acid on the basis of a theoretical calculation employing his exciton-chirality method.55 

2 Synthetic approaches to assign the S-configuration to (+)-abscisic acid 

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