作者:Daniel J. Leonard、John W. Ward、Jonathan Clayden
DOI:10.1038/s41586-018-0553-9
日期:2018.10
α-aryl amino acids and their derivatives are valuable precursors to bioactive molecules10,11. Here we describe the synthesis of quaternary α-aryl amino acids from enantiopure amino acid precursors by α-arylation without loss of stereochemical integrity. Our approach relies on the temporary formation of a second stereogenic centre in an N′-arylurea adduct12 of an imidazolidinone derivative6 of the precursor
Chemistry and folding of photomodulable peptides – stilbene and thioaurone-type candidates for conformational switches
作者:Máté Erdélyi、Miranda Varedian、Christian Sköld、Ida B. Niklasson、Johanna Nurbo、Åsa Persson、Jonas Bergquist、Adolf Gogoll
DOI:10.1039/b812001c
日期:——
Optimized synthetic strategies for the preparation of photoswitchable molecular scaffolds based on stilbene or on thioaurone chromophores and their conformationally directing properties, as studied by computations and by NMR spectroscopy, are addressed. For the stilbene peptidomimetics 1, 2 and 3, the length of connecting linkers between the chromophore and the peptide strands was varied, resulting in photochromic dipeptidomimetics with various flexibility. Building blocks of higher rigidity, based on para-substituted thioaurone (4 and 6) and meta-substituted thioaurone chromophores (5 and 7) are shown to have a stronger conformationally directing effect. Design, synthesis, theoretical and experimental conformational analyses are presented.
An Aliphatic Bischler–Napieralski Reaction: Dihydropyridones by Cyclocarbonylation of 3-Allylimidazolidin-4-ones
作者:Mostafa M. Amer、Olatz Olaizola、Jennifer Carter、Hossay Abas、Jonathan Clayden
DOI:10.1021/acs.orglett.9b04250
日期:2020.1.3
with potassium iodide led to cyclization of the allylic substituent onto the carbonyl group in an intramolecular aliphatic Friedel-Crafts-type acylation that corresponds to an aliphatic Bischler-Napieralskireaction. The product 3,4-dihydropyridinones were amenable to further functionalization, and finally hydrolysis, to deliver a series of enantio-enriched pipecolic acid derivatives.
A Bifunctional Photoaminocatalyst for the Alkylation of Aldehydes: Design, Analysis, and Mechanistic Studies
作者:Thomas Rigotti、Antonio Casado-Sánchez、Silvia Cabrera、Raúl Pérez-Ruiz、Marta Liras、Víctor A. de la Peña O’Shea、José Alemán
DOI:10.1021/acscatal.8b01331
日期:2018.7.6
visible light conditions. To corroborate the experimental observations, ground state geometry optimization and energy transition studies of thioxanthone and bifunctional catalyst 4c were optimized by time-dependent density functional theory (TD DFT) calculations. The alkylation of aldehydes with this photoaminocatalyst works with high enantioselectivities and yields due to the stereoelectronic properties
Pyrrolidine ring puckering and prolyl amide bond configurations of 2-methyl-allo-hydroxyproline-based dipeptides
作者:Vinay Shankar Tiwari、Gajendra Singh、Gurudayal Gurudayal、Ravi Sankar Ampapathi、Wahajul Haq
DOI:10.1039/c9ob00150f
日期:——
2-methyl allo-hydroxyl prolines was developed using direct aminolysis of bicyclic lactones derived from d/l alanine. The impact of C-2 methylation and its spatial orientation on the pyrrolidine ringpuckering and prolyl amide bond configuration was ascertained by solution NMR studies. The present studies reveal that C-2 methylation causes the prolyl amide bond to exist exclusively in the trans geometry
使用衍生自d / l丙氨酸的双环内酯的直接氨解方法,开发了一种快速的方法,用于合成含有l-丙氨酸和d / l 2-甲基异羟丙基脯氨酸的同型和杂手性二肽。通过溶液NMR研究确定了C-2甲基化及其空间取向对吡咯烷环折叠和脯氨酰胺键构型的影响。本研究表明,C-2甲基化会导致脯氨酰胺键仅在反式几何结构中均存在于同手性和杂手性二肽中。但是,C-2甲基的空间取向及其在适当加帽的模型二肽中的i + 2位置可能成核为匝状结构。