Visible-light-induced phenylchalcogenyl-oxygenation of allenes having aryl or electron withdrawing substituents with ambient air as a sole oxidant.

The synthesis of regio- and stereoselective aryl substituted α,ß-unsaturated aldehydes and ketones from activated allenes was achieved. This mild and non-metallic oxidation is exclusively driven by benign ambient air and triggered by visible light. The same starting materials under ideal anaerobic conditions led to the 2,3-diphenylselenation adduct with no trace of oxygenated products, demonstrating dissolved oxygen as a chemical switch for two different reaction pathways. The salient feature of this protocol is the single electron transfer (SET) achieved by irradiation of one of two organic molecules thereby avoiding a sensitizer to form a radical ion pair.

Concise diastereoselective synthesis of calcaripeptide C via asymmetric transfer hydrogenation/Pd-induced chiral allenylzinc as a key reaction.

Synthesis of the natural product calcaripeptide C derived from the fungal metabolite mycelium KF525 of Calcarisporium sp. has been achieved. This complementary approach avoids the use of a stoichiometric amount of chiral auxiliary reagents as commonly used to generate enantioenriched advanced precursors. The enantioselective synthesis of calcaripeptide C is remarkable in that using catalytic reactions sets the two stereogenic centers efficiently with good levels of enantioselectivity. Further diversification of the calcaripeptide C structures is possible by employing a complementary catalytic enantioenriched Ru-catalyst.

A concise diastereoselective approach to enantioenriched substituted piperidines and their in vitro cytotoxicity evaluation.

A library of diversely stereo-oriented, highly substituted 2,6-cis piperidine derivatives were synthesized, and evaluated for their anticancer activity in cancer cells that included A549 (lung cancer, CCL-185), MCF7 (breast cancer (HTB-22), DU145 (prostate cancer (HTB-81), and HeLa (cervical cancer, CCL-2). One stereo-variant emerged as a promising candidate for further design based structure-activity studies.

Towards the diastereoselective synthesis of derivative of 11'-epi-brevipolide H.

An efficient diastereoselective synthesis of brevipolide H derivative is described. The approach features the use of (i) catalytic asymmetric transfer hydrogenation, (ii) hydroxyl-directed cyclopropanation, and (iii) substrate-controlled catalytic epoxidation and ring-closing metathesis. Remarkably, in this convergent synthesis process, stereogenic centers were installed through catalytic reactions with high stereocontrol, which greatly facilitates the synthesis of stereo-divergent derivatives.

Enantioselective synthesis of δ-/γ-alkoxy-ß-hydroxy-α-alkyl-substituted Weinreb amides via DKR-ATH: application to the synthesis of advanced intermediate of (-)-brevisamide.

A method of preparing stereodefined δ-/γ-alkoxy-ß-hydroxy-α-alkyl-substituted Weinreb amides containing two successive hydroxyl-alkyl stereocenters has been developed. Further, this strategy coupled with organo-catalyzed asymmetric epoxidation culminates in the synthesis of a critical intermediate of (-)-brevisamide and its diastereomers.

Cu(I)-catalyzed tandem benzyldiazoester coupling with terminal alkyne-allene formation-Michael reaction: application to the syntheses of oxa and azacycles.

A simple and practical procedure for the synthesis of aza- and oxacycles, which possess an array of stereogenic functionalities, is described. This protocol relies on tandem Cu-catalyzed coupling of suitably functionalized terminal alkyne with diazoester followed by isomerization and subsequent aza or oxa-Michael reaction, thus generating the required scaffold with high diastereoselectivity.

FeCl3-catalyzed oxidative allylation of sp2 and sp3 C-H bond adjacent to a nitrogen atom: easy access to homoallyl tertiary amines.

Oxidative allylation to sp(2)- and sp(3)-carbon attached to the nitrogen atom was accomplished. The alpha-allylation of tertiary amines was catalyzed by easily available hydrated iron(III) chloride in combination with air or aqueous (t)BuOOH. Remarkably, N-allyl- and N-propagyl-tethered tertiary amines were also allylated through this protocol.

An Organocatalyzed enantioselective synthesis of (2S,3R,4S)-4-hydroxyisoleucine and its stereoisomers.

A concise enantioselective total synthesis of (2S,3R,4S)-4-hydroxyisoleucine and its stereoisomers is described. A key feature of this protocol is a catalytic enantioselective mannich reaction that is either anti- or syn-selective as genesis of chirality.

A flexible enantioselective total synthesis of diospongins A and B and their enantiomers using catalytic hetero-Diels-Alder/Rh-catalyzed 1,4-addition and asymmetric transfer hydrogenation reactions as key steps.

A unified enantioselective route to total synthesis of diospongins A and B and their enantiomers has been developed employing achiral starting materials. All three stereocenters were introduced by means of catalytic reactions.

Cationic Pd(IV)-Induced Highly Diastereoselective Arylative Cascade Cyclization of Allene-Tethered Cyclohexadienones Leading to Oxygenated Bicyclic Motifs.

A cationic Pd(IV)-catalyzed arylative hydroxylation-Micheal addition of allenyl-tethered cyclohexadienones was developed. This relay reaction could afford highly diastereoselective various functionalized arylative 1,4-dioxane cis-bicyclic structural units with good to high yields. The striking features revealed from these studies is the necessity of Selectfluor and the oxidative hydroxylation originating from water initiated by F-Pd(IV) catalysis. A plausible mechanism was also proposed for this variant observation.

Highly enantioselective carbon-carbon bond formation by Cu-catalyzed asymmetric [2,3]-sigmatropic rearrangement: application to the syntheses of seven-membered oxacycles and six-membered carbocycles.

A concise route for the syntheses of enantioenriched functionalized scaffolds of medium-sized oxacycles and carbocycles employing the chiral auxiliary-mediated Cu-catalyzed ylide formation/[2,3]-sigmatropic rearrangement as a key step was developed.

Enantioselective total synthesis of eicosanoid and its congener, using organocatalytic cyclopropanation, and catalytic asymmetric transfer hydrogenation reactions as key steps.

An enantioselective unified strategy for the syntheses of the oxylipin class of natural products was accomplished. Our strategy relies on three catalytic steps: (a) organocatalytic cyclopropanation, (b) the catalytic asymmetric transfer hydrogenation (CATHy) reaction, and (c) the Nozaki-Hiyama-Kishi reaction.

Tandem epoxide or aziridine ring opening by azide/copper catalyzed [3+2] cycloaddition: efficient synthesis of 1,2,3-triazolo beta-hydroxy or beta-tosylamino functionality motif.

A novel and practical procedure for the synthesis of small molecules possessing beta-hydroxy or N-tosylamino 1,2,3-triazole motif by azidation of epoxides or N-tosylaziridines with sodium azide followed by "click reaction" using eco-friendly PEG-400 as a reaction medium in the presence of 5 mol % of CuI is described. Enantiomerically pure epoxide and N-tosylaziridines were afforded in high yield with excellent ee values maintaining complete stereospecificity.

Development and validation of a reversed-phase HPLC method for monitoring of synthetic reactions during the manufacture of a key intermediate of an anti-hypertensive drug.

A reversed-phase high-performance liquid-chromatographic method for monitoring of reactions involved in process development of a key intermediate of antihypertensive drugs, e.g, doxazosin mesylate, prazosin, alfuzosin, terazosin, etc., has been developed and validated. The HPLC profiles of impurities of 4-amino-2-chloro-6,7-dimethoxyquinazoline were used as fingerprints to follow the synthetic procedures in the manufacturing unit. The separation was accomplished on an Inertsil ODS-3 column with isocratic elution using acetonitrile-ammonium acetate (10 mM; pH 4.0; 50:50 v/v) as mobile phase and a photodiode array detector set at 240 nm at ambient temperature. The method was validated with respect to accuracy, precision, linearity, and limits of detection and quantification. The method could detect the impurities at a level of 0.01 to 0.20 microg/mL and it was found to be suitable not only for monitoring of reactions but also for quality assurance of 4-amino-2-chloro-6,7-dimethoxyquinazoline.

Oppolzer sultam directed aldol as a key step for the stereoselective syntheses of antitumor antibiotic belactosin C and its synthetic congeners.

[reaction: see text] An efficient protocol has been developed using D-(2R)-Oppolzer sultam as a chiral auxiliary for generating anti/syn diastereomers with high enantiopurity and utilized in the efficient synthesis of natural product belactosin C and their synthetic congeners. It has been observed that a variation in the stoichiometry of the Lewis acid led to a difference in anti/syn selectivity.