A radical mediated approach to the stereoselective formal total synthesis of (+)-Sch 642305

A formal total synthesis of (+)-Sch-642305 is described. The synthesis, which commenced from a simple chiral synthon (5S)-5-(hydroxymethyl)dihydrofuran-2(3H)-one, employed, as a key step, a radical mediated opening of a chiral epoxy alcohol intermediate with Cp2Ti(III)Cl following an efficient method developed by us earlier. The resultant intermediate radical was intramolecularly trapped by the electron deficient double bond present in the molecule to give rise to its highly functionalized six-membered carbocyclic ring in stereoselective manner

Ti(III)-mediated radical cyclization of β-aminoacrylate containing epoxy alcohol moieties: synthesis of highly substituted azacycles

Ti(III)-mediated radical cyclization of β-aminoacrylate containing 2,3-epoxy alcohol moieties led to the formation of highly substituted piperidine and pyrrolidine rings. The pyrrolidine ring system was then transformed into an indolizidine framework present in many natural products

Sugar amino acids and related molecules: some recent developments

To meet the growing demands for the development of new molecular entities for discovering new drugs and materials, organic chemists have started working on many new concepts that can help to assimilate knowledge-based structural diversities more efficiently than ever before. Emulating the basic principles followed by Nature to build its vast repertoire of biomolecules, organic chemists are developing many novel multifunctional building blocks and using them to create 'nature-like' and yet unnatural organic molecules. Sugar amino acids constitute an important class of such polyfunctional scaffolds where the carboxyl, amino and hydroxyl termini provide an excellent opportunity to organic chemists to create structural diversities akin to Nature's molecular arsenal. In recent years, sugar amino acids have been used extensively in the area of peptidomimetic studies. Advances made in the area of combinatorial chemistry can provide the necessary technological support for rapid compilations of sugar amino acidbased libraries exploiting the diversities of their carbohydrate frameworks and well-developed solid-phase peptide synthesis methods. This perspective article chronicles some of the recent applications of various sugar amino acids, furan amino acids, pyrrole amino acids etc. and many other related building blocks in wide-ranging peptidomimetic studies

Synthesis and structural studies of peptides containing a mannose-derived furanoid sugar amino acid

A mannose-derived furanoid sugar amino acid (Maa) induced helical turns in peptides having repeat units of Maa(Bn2)-Phe-Leu, which aggregated into head-to-tail duplexes in the longer oligomers

Total synthesis of (+)-conagenin

The total synthesis of the immunomodulator, (+)-conagenin was achieved using, as a key step, a method developed by us for the synthesis of 2-methyl-1,3-diols via Ti(III)-mediated diastereo- and regioselective opening of trisubstituted 2,3-epoxy alcohols, to carry out the stereoselective construction of its pentanoic acid segment

Total synthesis of hyptolide

The total synthesis of hyptolide, a naturally occurring α,β-unsaturated six-membered δ-lactone substituted with a polyoxygenated chain, is described. Sharpless kinetic resolution and opening of two different epoxy alcohols under two different conditions-Swern oxidation conditions and a radical reaction using Cp2TiCl-fixed the stereocenters at C-9, C-11, and C-12, respectively. Brown's asymmetric allylation reaction installed the remaining stereocenter at C-6. A RCM protocol was used for construction of the α,β-unsaturated six-membered δ-lactone moiety of the molecule

Synthesis of C6-substituted 3,4-dideoxy furanoid sugar amino acids

A variety of chiral 3,4-dideoxy furanoid sugar amino acids have been synthesized, which were substituted at C6 with different alkyl groups, such as methyl, benzyl, isopropyl and hydroxymethyl synthesized from their corresponding N,N-dibenzylaminoaldehydes

An overview of the recent synthetic studies toward penifulvins and other fenestranes

Complex natural products provide a useful template for the construction of novel molecular scaffolds of biological as well as theoretical interest. In this regard, fenestranes have emerged as a challenging target for organic chemists. The existence of the planarized distortion of the central quaternary carbon in fenestranes away from its standard tetrahedral bond angle makes their synthesis a daunting task. In this review, an attempt has been made to capture the essence of some recent synthetic studies toward these molecules with an emphasis on penifulvins, the first 5.5.5.6]dioxafenestrane. (C) 2016 Elsevier Ltd. All rights reserved

Toward the total synthesis of a lagunamide B analogue

Lagunamides, isolated from a marine cyanobacterium Lyngbya majuscule found in Singapore, showed very potent activities against Plasmodium falciparum and murine leukemia cell line (P388). Herein, a concise synthetic approach toward the total synthesis of a lagunamide B analogue is discussed. Macrolactonization, HWE-olefination, and modified Crimmin's aldol are some of the key reactions featured in this synthesis. (C) 2014 Elsevier Ltd. All rights reserved

Synthesis of Amide-Linked Cyclic Dinucleotide Analogues with Pyrimidine Bases

A convenient procedure has been developed for the synthesis of C-2-symmetrical cyclic dinucleotide analogues that contain all-pyrimidine bases (cytosine, uracil and thymine) with amide bonds in place of natural phosphodiester linkages, starting from commercially available d-glucose diacetonide (GDA). The Vorbruggen glycosylation of a common intermediate by using various pyrimidine bases was employed as the key step in the synthesis