Sadagopan Raghavan

Solid-phase synthesis of pyrrolo[2,1-c][1,4]benzodiazepine-5,11-diones

The solid-phase synthesis of biologically important pyrrolo[2,1-c][1,4]benzodiazepine-5,11-diones using Wang resin through amide formation and reductive cyclization procedures is described. Further, N10-substituents have been introduced in the final products and these have been cleaved from the solid support in good yields.

CATALYTIC OXIDATION OF THIOLS TO DISULFIDES WITH VANADYL ACETYLACETONATE (VO(ACAC)2)

Catalytic amounts of VO(acac)2 coupled with t-butylhydroperoxide chemoselectively oxidizes thiols to disulfides under mild reaction conditions and is generally useful for a wide variety of thiols. *IICT communication No. 4400.

Solid-phase synthesis of 1,4-diketones by thiazolium salt promoted addition of aldehydes to chalcones☆

The first report of thiazolium salt promoted Michael addition of aldehydes to chalcones (Stetter reaction) on solid-phase is reported. Reaction conditions have also been devised for cleaving the product 1,4-diketone from the solid-support in good yield and high purity.

The sulfinyl moiety as an intramolecular nucleophile. Part 3: Synthesis of (−)-muricatacin

Abstract A short, efficient and highly stereoselective synthesis of (−)-( R , R )-muricatacin is reported. The key steps include a highly diastereoselective reduction of a β-ketosulfoxide to a β-hydroxy sulfoxide, regio- and stereoselective bromohydration of an olefin employing the sulfinyl group as an internal nucleophile and chemoselective reduction of a double bond in the presence of a halogen atom.

An Efficient Stereoselective Synthesis of Penaresidin A from (E)-2-Protected Amino-3,4-unsaturated Sulfoxide

An efficient, modular, asymmetric synthesis of penaresidin A is disclosed. A beta-protected amino-gamma,delta-unsaturated sulfoxide was prepared by stereoselective addition of the lithio anion of (R)-methyl p-tolyl sulfoxide to an unsaturated sulfinylimine. The pendant sulfoxide group was used as an intramolecular nucleophile to functionalize an alkene regio- and stereoselectively to furnish a bromohydrin, which was employed as the key intermediate in the preparation of the azetidine subunit of penaresidin A. The stereogenic centers of the side chain were introduced by a regioselective opening of an epoxide. Julia-Kocienski olefination was used to couple the azetidine and side chain subunits. The methodology disclosed herein is also useful for the synthesis of ribo- and arabino-phytosphingosines and compounds possessing the amino alcohol moiety.

Efficient solid-phase synthesis of DNA-interactive pyrrolo[2,1-c][1,4]benzodiazepine antitumour antibiotics

The solid-phase synthesis of DNA-interactive pyrrolo[2,1-c][1,4]benzodiazepine (PBD) imines and biologically important pyrrolo[2,1-c][1,4]benzodiazepine-5,11-diones on Wang resin using a reduction/cyclization procedure is reported.

Novel, efficient and stereospecific synthesis of xylo-(2R,3S,4S)-phytosphingosine and threo-(2R,3R)-sphingosine ☆

Abstract The stereo- and regioselective elaboration of a bromohydrin from an olefinic precursor and Pummerer ene reaction for carboncarbon bond formation are the key steps in a novel and flexible synthesis of xylo -phytosphingosine and threo -sphingosine.

Asymmetric Synthesis of the Potent HIV-Protease Inhibitor, Nelfinavir

An asymmetric synthesis of nelfinavir is described starting from acrolein and (S)-methyl phenyl sulfoxide. The key features include (a) stereoselective preparation of a beta-protected amino-gamma,delta-unsaturated sulfoxide by the reaction of an alpha-sulfinyl carbanion with an unsaturated t-butyl sulfinylimine, (b) stereoselective bromohydrin formation using the pendant sulfoxide group as an intramolecular nucleophile, and (c) use of commercially or readily prepared inexpensive starting materials.

Total Synthesis of (+)‐(2′S,3′R)‐Zoapatanol Exploiting the B‐Alkyl Suzuki Reaction and the Nucleophilic Potential of the Sulfinyl Group

A stereoselective synthesis of the diterpenoid oxepane (+)-zoapatanol is described. The key steps include a B-alkyl Suzuki cross-coupling reaction for the stereoselective synthesis of trisubstituted alkenes, creation of the two stereogenic centers on the oxepane ring by heterofunctionalization of an alkene through substrate control exploiting the nucleophilic potential of an intramolecular sulfinyl group, and transformation of a β-hydroxy sulfoxide into a terminal alkene.

Sulfinyl moiety as an internal nucleophile. Part 6: Stereospecific synthesis of 3-amino-2-hydroxy-4-phenylbutanoate ☆

A novel and stereospecific synthesis of (2R,3S)-3-amino-2-hydroxy-4-phenylbutanoate (AHPBA) is disclosed. The key step includes regio- and stereospecific functionalization of an alkene by the pendant sulfinyl group.