Organocatalytic Enantiospecific Total Synthesis of Butenolides

Biologically important, chiral natural products of butenolides, (−)-blastmycinolactol, (+)-blastmycinone, (−)-NFX-2, (+)-antimycinone, lipid metabolites, (+)-ancepsenolide, (+)-homoancepsenolide, mosquito larvicidal butenolide and their analogues were synthesized in very good yields in a sequential one-pot manner by using an organocatalytic reductive coupling and palladium-mediated reductive deoxygenation or organocatalytic reductive coupling and silica-mediated reductive deamination as the key steps

A Brønsted Acid-Amino Acid as a Synergistic Catalyst for Asymmetric List-Lerner-Barbas Aldol Reactions

Herein, for the first time, a combination of l-amino acid, (<i>R</i>)-5,5-dimethyl thiazolidinium-4-carboxylate (l-DMTC) with simple Brønsted acid TFA is reported as the suitable synergistic catalyst for the List-Lerner-Barbas aldol (LLB-A) reaction of less reactive 2-azidobenzaldehydes with various ketones at ambient temperature to furnish the optically active functionalized (2-azido­phenyl)­alcohols with very good yields, dr’s, and ee’s. This method gives first time access to the novel azido-containing multifunctional compounds, which are applicable in material to medicinal chemistry. Chiral functionalized (2-azido­phenyl)­alcohols were transformed into different molecular scaffolds in good yields with high selectivity through Lewis acid mediated NaBH₄ reduction, aza-Wittig and Staudinger reaction (azide reduction), followed by oxidative cyclizations, allenone synthesis, and click reaction, respectively. Chiral LLB-A products might become suitable starting materials for the total synthesis of natural products, ingredients, and inhibitors in medicinal chemistry. The mechanistic synergy of l-DMTC with TFA to increase the rate and selectivity of LLB-A reaction in DMSO-D₆ is explained with the controlled and online NMR experiments

Rawal's catalyst as an effective stimulant for the highly asymmetric Michael addition of β-keto esters to functionally rich nitro-olefins

A general approach to the asymmetric synthesis of highly substituted dihydroquinolines was achieved through neighboringortho-amino group engaged sequential Michael/amination/dehydration reactions.</p

Unraveling the Stability of Plasma Proteins upon Interaction of Synthesized Androstenedione and Its DerivativesA Biophysical and Computational Approach

4-Androstene-3-17-dione (4A), also known as androstenedione, is the key intermediate of steroid metabolism. 5β-Androstane-3-17-dione (5A) and (+)-6-methyl-5β-androstane-3-17-dione (6M) are the steroid derivatives of androstenedione. The interactions of androstenedione and its derivatives with plasma proteins are important in understanding the distribution and bioavailability of these molecules. In our present study, we have studied the binding affinity of androstenedione and its derivatives with plasma proteins such as human serum albumin (HSA) and α1-acid glycoprotein (AGP). Our results showed that the 4A, 5A, and 6M steroid molecules can form stable complexes with HSA and AGP. The affinity of the studied steroid molecules with HSA is high compared to that with AGP, and the binding constants obtained for 4A, 5A, and 6M with HSA are 5.3 ± 2 × 10⁴, 5.3 ± 1 × 10⁴, and 9.5 ± 0.2 × 10⁴ M^–1, respectively. Further, binding sites of these steroid molecules in HSA are identified using molecular displacement and docking studies: it is found that 4A and 5A bind to domain III while 6M binds to domain II of HSA. Furthermore, the circular dichroism data revealed that there is a partial unfolding of the protein while interacting with androstenedione and its derivatives. Also, molecular dynamics simulations were carried out for HSA–androstenedione and its derivative complexes to understand their stability; hence, these results yielded that HSA–androstenedione and its derivative complexes were stabilized after 15 ns and maintained their stable structures