Free radical 5-exo-dig cyclization as the key step in the synthesis of bis-butyrolactone natural products: experimental and theoretical studies

Radical cyclization reactions were performed by 5-exo-dig mode to yield cis-fused bicyclic systems, leading to the synthesis of bis-butyrolactone class of natural products. The study was aimed at understanding the impact of alkyl side chains of furanoside ring systems in L-ara configuration on the radical cyclization. It was amply demonstrated by experimental studies that the increase in the length of the alkyl side chain has an effect on the cyclization: while efficient cyclization reactions could be realized with methyl and ethyl side chains, the yields were significantly reduced in the case of n-pentyl side chain. Theoretical studies using DFT and (RO)MP2 methods were carried out to analyze the influence of the substitution pattern on the cyclization barriers

Studies Toward the Stereoselective Synthesis of C13 to C21 Fragment of the Brasilinolides Family of Immunosuppressive Macrolides

<div><p></p><p>The work describes our attempts to synthesize the C13 to C21 fragment of brasilinolides, a 32-membered macrolide class of molecule. The C13 to C21 segment encompasses six asymmetric centers and a pyran ketal moiety. The synthesis starts from L-malic acid, and the salient features of our asymmetric synthesis are opening of epoxide, assymmetric dihydroxylation for the creation of <i>vic</i>-diol, and Barbier allylation.</p></div

Stereoselective total synthesis of sporiolide B and attempted synthesis of sporiolide A

<p>A simple and efficient stereoselective total synthesis of sporiolide B and attempted synthesis of sporiolide A, from epichlorohydrin, using asymmetric synthetic approach is reported. The key reactions involved are Sharpless epoxidation, Jacobsen reaction, <i>syn</i>-allylation, Yamaguchi esterification, and Grubbs ring-closing metatheses reaction to result in the macrocyclic ring system.</p

Synthesis of <i>cis</i>-Fused Bicyclic Systems by Radical Cyclization Approach: Formal Synthesis of Ethisolide and <i>iso</i>-Avenaciolide

<div><p></p><p>Formal synthesis of ethisolide and <i>iso</i>-avenaciolide was achieved using furanoid glycal-vinyl radical intermediates. The vinyl radical cyclization by 5-<i>exo-</i>dig mode gave the <i>cis</i>-fused bicyclic systems with an efficient introduction of the <i>exo</i>-methylene group, besides helping in the inversion of the adjacent stereocentre. Further, the study describes the synthesis of <i>cis</i>-fused bicyclic systems from L-arabinose and D-xylose for the creation of diverse natural and synthetic products of this class.</p> </div

Regio- and stereocontrolled access to γ-boronated unsaturated amino esters and derivatives from (Z)-alkenyl 1,2-bis(boronates).

International audienceThe Borono-Mannich reaction of (Z)-1-alkene-1,2-diboronic esters proceeded regioselectively at the terminal C-B bond to afford (E)-γ-boronated unsaturated amino esters in good yields. These compounds were then subjected to Suzuki couplings for the creation of diversely substituted olefinic amino acid systems. Several other functional transformations were also carried out to illustrate the synthetic utility of the Petasis products

Synthesis of Polysubstituted Isoquinolines and Related Fused Pyridines from Alkenyl Boronic Esters via a Copper-Catalyzed Azidation/Aza-Wittig Condensation Sequence

International audienceAn efficient and straightforward synthesis of isoquinolines is reported from internal alkenyl boronic esters, easily prepared from the corresponding 1,2-bis(boronates), via a sequential copper-catalyzed azidation/aza-Wittig condensation. This synthetic method has been used to synthesize quinisocaine, a topical anesthetic used for the treatment of pain and pruritus, and further extended to thieno[2,3-c]pyridines by using 2-thiophenecarboxaldehyde as coupling partner in the first step

Synthesis of Novel Pyran β-Amino Acid and 5,6-Dihydro-2H-pyran β-aminoxy Acid from Carbohydrate Derivatives

<div><p></p><p>Synthesis of two new amino acids, containing pyran rings, is reported from carbohydrate derivatives. The <i>cis</i>-3-amino-pyran-2-carboxylic acid (<i>cis</i>-APyC) was prepared from (<i>R</i>)-glyceraldehyde derivative, using nucleophilic substitution reaction for pyran ring formation. Similarly, the <i>trans</i>-3-aminoxy-5,6-dihydro-2H-pyran-2-carboxylic acid (<i>trans</i>-AmPyC) was prepared from diacetone glucose (DAG), using ring closing metathesis (RCM) reaction for the ring formation.</p></div