Synthesis of Novel Azidocastasterone Derivative as a Potential Photoaffinity Label for the Brassinosteroid Receptor
作者:Thomas G. Back、Kazimierz Minksztym
DOI:10.1055/s-1999-2585
日期:1999.2
(22R,23R,24R)-24-Azido-26,27,28-trinorcastasterone (3) was synthesized from stigmasterol in 12 steps via the reaction of Ti(O-iPr)2(N3)2 with the corresponding suitably protected threo-22-hydroxy-23,24-epoxide 4.
Effect of Chain Length and Ring Size of Alkyl and Cycloalkyl Side-Chain Substituents upon the Biological Activity of Brassinosteroids. Preparation of Novel Analogues with Activity Exceeding that of Brassinolide
作者:Thomas G. Back、Loeke Janzen、Suanne K. Nakajima、Richard P. Pharis
DOI:10.1021/jo9917947
日期:2000.5.1
tellurium and lithium triethylborohydride. The rice leaf lamina inclination assay was then used to measure the bioactivity of the products. In general, increasing activity was observed as the length or ringsize of the C-24 hydrocarbon substituent decreased. The novel cyclobutyl- and cyclopropyl-substituted analogues of brassinolide (1) were ca. 5-7 times as active as 1 and thus appear to be the most potent
A new synthesis of castasterone and brassinolide from stigmasterol. A concise and stereoselective elaboration of the side chain from a C-22 aldehyde
作者:Thomas G. Back、Peter G. Blazecka、M. Vijaya Krishna
DOI:10.1139/v93-022
日期:1993.2.1
Brassinolide (1) and castasterone (2) were prepared from aldehyde 7, in turn available from stigmasterol (3). The addition of (E)-1-propenyllithium to 7, followed by diastereoselective Sharpless epoxidation of allylic alcohol 8 using (L)-(+)-diethyl tartrate, and regioselective epoxide-opening of (threo) epoxy alcohol 15 with isopropylmagnesium chloride in the presence of a catalytic amount of cuprous