1-Alkyl-2,4-dihydro-1H-pyrazino[2,1-b]quinazoline-3,6-diones as glycine templates. Synthesis of Fiscalin B
作者:Fernando Hernández、Félix L. Buenadicha、Carmen Avendaño、Mónica Söllhuber
DOI:10.1016/s0957-4166(02)00027-7
日期:2002.1
An excess of base allows the regio- and diastereoselective alkylation at C(4) of the glycine templates 1-methyl(isopropyl)-2,4-dihydro-1H-pyrazino[2,1-b]quinazoline-3,6-diones 9a and 9b without the need for N(2)-protecting groups. While the alkylation of 9a gave exclusively the 1,4-anti-isomers, the isopropyl derivative 9b required much longer reaction times and occurred with lower diastereoselectivity. Fiscalin B 3 was obtained by alkylation of 9b with N-Boc-3-indolylmethyl bromide followed by indole deprotection. (C) 2002 Elsevier Science Ltd. All rights reserved.
Intramolecular arylation of amino acid enolates
作者:Rachel C. Atkinson、Daniel J. Leonard、Julien Maury、Daniele Castagnolo、Nicole Volz、Jonathan Clayden
DOI:10.1039/c3cc46193a
日期:——
Dianionic enolates formed from N′-aryl urea derivatives of amino acids undergo intramolecular C-arylation by attack of the enolate anion on the N′-aryl ring, leading to a hydantoin derivative of a quaternary amino acid. In situ IR studies allow identification of four intermediates on the reaction pathway.