A versatile method for the preparation of conjugates of peptides with DNA/PNA/analog by employing chemo-selective click reaction in water

The specific 1,3 dipolar Hüisgen cycloaddition reaction known as ‘click-reaction’ between azide and alkyne groups is employed for the synthesis of peptide–oligonucleotide conjugates. The peptide nucleic acids (PNA)/DNA and peptides may be appended either by azide or alkyne groups. The cycloaddition reaction between the azide and alkyne appended substrates allows the synthesis of the desired conjugates in high purity and yields irrespective of the sequence and functional groups on either of the two substrates. The versatile approach could also be employed to generate the conjugates of peptides with thioacetamido nucleic acid (TANA) analog. The click reaction is catalyzed by Cu (I) in either water or in organic medium. In water, ∼3-fold excess of the peptide-alkyne/azide drives the reaction to completion in 2 h with no side products

A comprehensive study on the effect of acid additives in 1(<i style="mso-bidi-font-style:normal">R</i>),2(<i style="mso-bidi-font-style: normal">R</i>)-Bis[(<i style="mso-bidi-font-style:normal">S</i>)-prolinamido]cyclohexane catalyzed direct asymmetric aldol reactions in aqueous media

84-92The catalytic efficacy of (1R,2<i style="mso-bidi-font-style: normal">R)-bis[(S)-prolinamido]cyclohexane 1, prepared from the readily available natural amino acid -proline has been studied for the direct asymmetric aldol reaction of cyclohexanone with substituted benzaldehydes at room temperature in presence of various acid additives. A wide variety of acids e.g. aliphatic fatty acid, chiral acid, sulphonic acid, aromatic acid, etc. have been used as additive for the aldol reaction in aqueous media. A loading of 10 mol% of catalyst 1 is employed in this reaction, and good yields (up to 98% yield), diastereoselectivity (up to 96% de) and enantioselectivities (up to 87% ee) can be achieved in aqueous media within very short reaction time (1-4 hours)

Regioselective NaBH₄ and DIBAL-H reductions of 3,4-dimethoxyhomopiperonyl­phthalimide: Concise and efficient synthesis of nuevamine and isonuevamine

868-871Facile synthesis of nuevamine and isonuevamine has been reported via the regioselective reduction of hindered and un­hindered carbonyl groups of 3,4-dimethoxyhomopiperonyl­ph­thalimide, respectively using sodium borohydride and di­isobutyl­­aluminum hydride, followed by an acid catalyzed intra­molecular dehydrative cyclization pathways. The chemistry involved in obtaining the regioselectivity has been discussed in brief

Asymmetric N‑Heterocyclic Carbene (NHC)-Catalyzed Annulation of Modified Enals with Enolizable Aldehydes

N-Heterocyclic carbene (NHC)-catalyzed highly enantioselective lactonization of modified enals with enolizable aldehydes, proceeding via the α,β-unsaturated acylazolium intermediates, is reported. The reaction results in the asymmetric synthesis of synthetically important 4,5-disubstituted dihydropyranones