Synthesis 2017; 49(05): 1037-1042
DOI: 10.1055/s-0036-1588907
paper
© Georg Thieme Verlag Stuttgart · New York

Blue Amino Acids Derived from Azulen-1-ylboronic Acid Pinacol Ester via the Petasis Reaction

Toshihiro Murafuji*
a   Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Yamaguchi 753-8512, Japan   Email: murafuji@yamaguchi-u.ac.jp
b   Graduate School of Medicine, Yamaguchi University, Yamaguchi 753-8512, Japan
,
Yusuke Tasaki
b   Graduate School of Medicine, Yamaguchi University, Yamaguchi 753-8512, Japan
,
Masayuki Fujinaga
b   Graduate School of Medicine, Yamaguchi University, Yamaguchi 753-8512, Japan
,
Keisuke Tao
c   Graduate School of Science and Engineering, Yamaguchi University, Yamaguchi 753-8512, Japan
,
Shin Kamijo
a   Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Yamaguchi 753-8512, Japan   Email: murafuji@yamaguchi-u.ac.jp
c   Graduate School of Science and Engineering, Yamaguchi University, Yamaguchi 753-8512, Japan
,
Katsuya Ishiguro
a   Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Yamaguchi 753-8512, Japan   Email: murafuji@yamaguchi-u.ac.jp
c   Graduate School of Science and Engineering, Yamaguchi University, Yamaguchi 753-8512, Japan
› Author Affiliations
Further Information

Publication History

Received: 06 September 2016

Accepted after revision: 04 October 2016

Publication Date:
22 November 2016 (online)


Abstract

Azulen-1-ylboronic acid pinacol ester undergoes a three-component Petasis reaction with amines and glyoxylic acid hydrate to give azulenylglycine derivatives in good yields. The progress of the reaction is indicated by a characteristic color change from violet to blue due to the altered π-conjugation of the azulene chromophore. The azulenylboronic ester is more reactive than its phenyl counterpart and even 2-styryl- and 2-thienylboronic pinacol esters, which have a strong electron-donating organyl group on boron. These results reflect the unique π-electron system of non-alternant azulene.

Supporting Information