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Photoracemization of Blestriarene C and Its Analogs
Author(s) -
Natori Koichi,
Iwayama Taizo,
Yamabe Osamu,
Kitamoto Yuichi,
Ikeda Hiroshi,
Sakamoto Kenkichi,
Hattori Tetsutaro,
Miyano Sotaro
Publication year - 2015
Publication title -
chirality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.43
H-Index - 77
eISSN - 1520-636X
pISSN - 0899-0042
DOI - 10.1002/chir.22447
Subject(s) - racemization , chemistry , cyclic voltammetry , redox , photochemistry , stereochemistry , fluorescence , medicinal chemistry , organic chemistry , electrochemistry , electrode , physics , quantum mechanics
Two analogs of blestriarene C (4,4'‐dimethoxy‐1,1'‐biphenanthrene‐2,2',7,7'‐tetraol) bearing no 7,7'‐dihydroxy ( 3 ) and 4,4'‐dimethoxy groups 4 were prepared. Unlike blestriarene C ( 1 ), compounds 3 and 4 , as well as 1,1'‐biphenanthrene‐2,2'‐diol ( 5 ), do not racemize under fluorescent lamp illumination. Cyclic voltammetry analysis reveals that compound 1 has a lower half‐wave potential ( E 1/2 ) than compounds 3 , 4 , 5 , suggesting that a redox cycle is involved in the racemization . Compound 1 racemizes by absorbing UV light corresponding to the 1 L b band. During the reaction, no side products are observed. The racemization is significantly inhibited under nitrogen. Based on these observations, we propose a feasible mechanism for the easy racemization of compound 1 , which is mediated by a cation radical generated in situ by a reversible photo‐induced oxygen oxidation. Chirality 27:479–486 , 2015 . © 2015 Wiley Periodicals, Inc.