2407-11-6Relevant articles and documents
Stereodivergent, Diels-Alder-initiated organocascades employing α,β-unsaturated acylammonium salts: scope, mechanism, and application
Abbasov, Mikail E.,Hudson, Brandi M.,Tantillo, Dean J.,Romo, Daniel
, p. 1511 - 1524 (2017)
Chiral α,β-unsaturated acylammonium salts are novel dienophiles enabling enantioselective Diels-Alder-lactonization (DAL) organocascades leading to cis- and trans-fused, bicyclic γ- and δ-lactones from readily prepared dienes, commodity acid chlorides, and a chiral isothiourea organocatalyst under mild conditions. We describe extensions of stereodivergent DAL organocascades to other racemic dienes bearing pendant secondary and tertiary alcohols, and application to a formal synthesis of (+)-dihydrocompactin is described. A combined experimental and computational investigation of unsaturated acylammonium salt formation and the entire DAL organocascade pathway provide a rationalization of the effect of Br?nsted base additives and enabled a controllable, diastereodivergent DAL process leading to a full complement of possible stereoisomeric products. Evaluation of free energy and enthalpy barriers in conjunction with experimentally observed temperature effects revealed that the DAL is a rare case of an entropy-controlled diastereoselective process. NMR analysis of diene alcohol-Br?nsted base interactions and computational studies provide a plausible explanation of observed stabilization of exo transition-state structures through hydrogen-bonding effects.
Synthesis of N-Peptide-6-Amino-d-Luciferin Conjugates with Optimized Fragment Condensation Strategy
Kovács, Anita K.,Hegyes, Péter,Szebeni, Gábor J.,Bogár, Krisztián,Puskás, László G.,Tóth, Gábor K.
, p. 1209 - 1215 (2018/09/27)
Abstract: The synthesis of peptide-luciferin conjugates has a pivotal role in the development of bioluminescent detection systems that are based on the determination of protease enzyme activity. This work describes the optimized synthesis of an N-peptide-6-amino-d-luciferin conjugate (Fmoc-Gly-Pro-6-amino-d-luciferin) with a simple fragment condensation method in adequate yields. Fmoc-Gly-Pro-6-amino-d-luciferin was produced from a previously synthesized Fmoc-Gly-Pro-OH and also previously synthesized 6-amino-2-cyanobenzothiazole with an optimized method, to which conjugate cysteine was added in an also improved way. The resulting conjugate was successfully used in a bioluminescent system, in vitro, demonstrating the applicability of the method. Graphical Abstract: [Figure not available: see fulltext.].
General Entry into o-,o′-Heteroatom-Linked N-(Hetero)aryl-Imidazole Motifs by Gold-Catalysed Formal [3+2]-Dipolar Cycloaddition
Garzón, Miguel,Arce, Elsa M.,Reddy, Raju Jannapu,Davies, Paul W.
supporting information, p. 1837 - 1843 (2017/06/09)
A general redox-neutral approach into the o-,o′-heteroatom-linked N-(hetero)aryl-imidazole family of heteroaromatics has been developed. New types of heteroatom substituted carbimidoyl nitrenoids are efficiently realised from robust, bench-stable N-(heteroaryl)-pyridinium-N-aminides by formal gold-catalysed [3+2]-dipolar cycloadditions across ynamides. Broad structural variety and functional group tolerance allows rapid access into diverse functionalised scaffolds, as exemplified by the preparation of 8 different heteroaromatic cores. (Figure presented.).
