New Amino Acids for the Topographical Control of Peptide Conformation: Synthesis of All the Isomers of .alpha.,.beta.-Dimethylphenylalanine and .alpha.,.beta.-Dimethyl-1,2,3,4-tetrahydroisoquinoline-3-carboxylic Acid of High Optical Purity
摘要:
The synthesis of all four diastereoisomers of alpha,beta-dimethylphenylalanine (4) as well as those of alpha,beta-dimethyl-1 ,2,3,4,-tetrahydroisoquinoline-3-carboxylic acid (5 and 6) have been accomplished in high yield and high optical purity. Molecular mechanics calculations on the N-alpha-acetyl and N- methylcarboxamide derivatives of (3R,4R)-6 and (3R,4S)-5 indicate large and moderate energy stabilization for the gauche(-) but not the gauche(+) side-chain conformers of (3R,4S)-5 and (3R,4R)-6, respectively. By symmetry rules, the same holds for (3S,4R)-5 and (3S,4S)-6, respectively. Thus, these amino acids are potential building blocks for the topographical design of peptides (Kazmierski et al., J. Am. Chem. Sec. 1991, 113, 2275-2283) by providing acylated 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid derivatives in which a gauche(-) and not a gauche(+) side-chain conformation is energetically more stable for the L amino acid. Synthetic details and implications of these new amino acids for peptide and protein design are discussed.
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.
Amino Acid-Derived <i>trans</i>-<i>N</i>-Chloroformylimidazolidinones: Scalable, Stereoselective Synthesis, Structure, and Utility
作者:Mostafa Mahmoud Amer、Hossay Abas、Daniel J. Leonard、John W. Ward、Jonathan Clayden
DOI:10.1021/acs.joc.9b00727
日期:2019.6.7
N-acyl imidazolidinones, which are key intermediates in the stereoselective synthesis of amino acids by “self-regeneration of stereochemistry” methods, are classically made by only moderately diastereoselective methods. We now report that cyclization of pivaldimino-amides with phosgene in the presence of pyridine may be made fully diastereoselective for the trans-N-chloroformylimidazolidinones, and
Asymmetric and Geometry‐Selective α‐Alkenylation of α‐Amino Acids
作者:Hossay Abas、Josep Mas‐Roselló、Mostafa Mahmoud Amer、Derek J. Durand、Robin R. Groleau、Natalie Fey、Jonathan Clayden
DOI:10.1002/anie.201813984
日期:2019.2.18
Both E‐ and Z‐N′‐alkenyl urea derivatives of imidazolidinones may be formed selectively from enantiopure α‐amino acids. Generation of their enolate derivatives in the presence of K+ and [18]crown‐6 induces intramolecular migration of the alkenyl group from N′ to Cα with retention of double bond geometry. DFT calculations indicate a partially concerted substitution mechanism. Hydrolysis of the enantiopure
Organocatalytic regiospecific synthesis of 1H-indene-2-carbaldehyde derivatives: suppression of cycloolefin isomerisation by employing sterically demanding catalysts
作者:Hui Mao、Dong Wan Kim、Hun Yi Shin、Choong Eui Song、Jung Woon Yang
DOI:10.1039/c6ob01918h
日期:——
The regiospecific synthesis of 1H-indene-2-carbaldehyde derivatives was achieved through transition-metal-free, reductive cyclisation of ortho-formyl trans-cinnamaldehydes with Hantzsch ester in the presence of an aminocatalyst. In particular, cycloolefin isomerisation of the resulting products could be inhibited efficiently by the introduction of a stericallydemanding stereo-defined aminocatalyst
Scalable synthesis and coupling of quaternary α-arylated amino acids: α-aryl substituents are tolerated in α-helical peptides
作者:Daniel J. Leonard、Francis Zieleniewski、Isabelle Wellhöfer、Emily G. Baker、John W. Ward、Derek N. Woolfson、Jonathan Clayden
DOI:10.1039/d1sc01378e
日期:——
Quaternary amino acids are important tools for the modification and stabilisation of peptide secondary structures. Here we describe a practical and scalable synthesis applicable to quaternary alpha-arylated amino acids (Q4As), and the development of solid-phase synthesis conditions for their incorporation into peptides. Monomeric and dimeric α-helical peptides are synthesised with varying degrees of
季氨基酸是修饰和稳定肽二级结构的重要工具。在这里,我们描述了适用于季α-芳基化氨基酸(Q4As)的实用且可扩展的合成,以及将其掺入肽中的固相合成条件的开发。合成具有不同程度的 Q4A 取代的单体和二聚 α-螺旋肽,并使用生物物理方法检查其结构。 Q4A 的两种对映异构体在折叠单体和寡聚 α-螺旋肽中均具有耐受性,其中 ( R )-对映异构体比 ( S )-对映异构体稍稍耐受。