252026-09-8Relevant articles and documents
Total synthesis without protection: Three-step synthesis of optically active clavicipitic acids by a biomimetic route
Yokoyama, Yuusaku,Hikawa, Hidemasa,Mitsuhashi, Masaharu,Uyama, Aki,Hiroki, Yasuhiro,Murakami, Yasuoki
, p. 1244 - 1253 (2004)
A three-step synthesis of a mixture of optically active cis- and frans-clavicipitic acids 6, which are ergot alkaloids, was achieved, starting from 4-bromoindole (7) and dl-serine (dl-2). This short synthesis was made possible by omitting the protection and deprotection steps from the synthetic route. The key step was the spontaneous cyclization of 4-vinyltryptophan (10) formed from the Heck reaction of 4-bromotryptophan (8) with 2-methyl-3-buten-2- ol (9) in aqueous media. During this investigation, we also found that the palladium-catalyzed reaction of 8 with 9 showed an interesting pH dependence; under strongly basic conditions, the Heck reaction occurred to give a C 4-vinylated product 10, whereas an N-allylated product 19b was formed under neutral or weakly basic conditions. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
Syntheses without protection: A three-step synthesis of optically active clavicipitic acid by utilizing biomimetic synthesis of 4-bromotryptophan
Yokoyama, Yuusaku,Hikawa, Hidemasa,Mitsuhashi, Masaharu,Uyama, Aki,Murakami, Yasuoki
, p. 7803 - 7806 (2007/10/03)
The optically active clavicipitic acid (4), an ergot alkaloid, was synthesized by a three-step sequence from 4-bromoindole (1). The reaction of 1 with dl-serine (2) in the presence of Ac2O followed by enzymatic kinetic resolution gave (S)-4-bromotryptophan (3). The Heck reaction of 3 with 1,1-dimethylallylalcohol in aqueous media gave clavicipitic acid in one-pot.
