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We describe herein design, synthesis and conformational investigations of polypeptides attached on a rigid dimedone template. Two identical peptide chains are attached on a single carbon containing dimedone as a scaffold. Dimedone assists in controlling the secondary interactions through strong intramolecular helical C‐12 and C‐15 membered bifurcated hydrogen bonding on both the peptide chains along with propagating the helical architecture of the peptide chains attached. There exists a C‐6 hydrogen bonding for the single stranded peptides attached to dimedone. Extensive structural investigations involving single crystal X‐ray diffraction, solution‐state NMR and CD studies of oligopeptides have been undertaken. [ABSTRACT FROM AUTHOR]

Cascade cyclization of a 3-[(3-methylbut-2-enylamino)methyl]but-3-en-1-ol derivative with aldehydes in the presence of TMSOTf at 0 °C under mild conditions provides the corresponding spiropyrrolidine scaffolds in good yields. Similar cyclization of a 3-[(4-methylpent-3-enylamino)methyl]but-3-en-1-ol derivative with aldehydes affords the correponding spiropiperidine compounds. This is a new approach for the construction of biologically relevant spirocycles in a single-step process. [ABSTRACT FROM AUTHOR]

A C-O bond-formation reaction that proceeds through C-H functionalization of N, N-dialkylanilines at the ortho-position is presented. The iron-catalyzed selective ortho-benzoyloxylation follows a polar Friedel-Crafts-like mechanism and is sensitive to the nucleophilicity of the anilines. The benzoyloxylation of a variety of N, N-disubstituted anilines and N-phenyl heterocycles is carried out under extremely mild conditions. Furthermore, the methodology has been successfully employed for the generation of 1,4-benzoxazepines and o-aminophenols. [ABSTRACT FROM AUTHOR]

Hybrid peptidic oligomers comprising natural and unnatural amino acid residues that can exhibit biomolecular folding and hydrogen-bonding mimicry have attracted considerable interest in recent years. While a variety of hybrid peptidic helices have been reported in the literature, other secondary structural patterns such as γ-turns and ribbons have not been well explored so far. The present work reports the design of novel periodic γ-turns in the oligomers of 1:1 natural- α/unnatural trans-β-norborenene (TNAA) amino acid residues. Through DFT, NMR, and MD studies, it is convincingly shown that, in the mixed conformational pool, the heterogeneous backbone of the hybrid peptides preferentially adopt periodic 8-membered (pseudo γ-turn)/7-membered (inverse γ-turn) hydrogen bonds in both polar and non-polar solvent media. It is observed that the stereochemistry and local conformational preference of the β-amino acid building blocks have a profound influence on accessing the specific secondary fold. These findings may be of significant relevance for the development of molecular scaffolds that facilitate desired positioning of functional side-chains. [ABSTRACT FROM AUTHOR]

The stereoselective total synthesis of dinemasone A has been accomplished. The key reactions, Sharpless asymmetric epoxidation, lithium-mediated epoxy alcohol opening, and double-intramolecular hetero-Michael addition, gave access to dinemasone A from lactic acid esters. The stereochemistry at the spiro carbon was determined using extensive NMR studies. [ABSTRACT FROM AUTHOR]