Synthesis of Diverse -Trifluoromethyl Pyrazoles by Trapping of Transiently-Generated Trifluoromethylhydrazine.

A one-pot synthesis of functionalized -trifluoromethyl pyrazoles from readily available di-Boc trifluoromethylhydrazine and dialdehydes, diketones, carbonylnitriles, and ketoesters/amides/acids is described. F NMR studies were used to characterize the stability of trifluoromethylhydrazine HCl salt in solution and in solid form and identified a short solution-state half-life of ∼6 h. Optimization of cyclization conditions identified DCM, combined with a strong acid, as a key to suppress the undesired des-CF side products, which formed as a result of the instability of trifluoromethylhydrazine and related intermediates.

Total Synthesis of Δ(12) -Prostaglandin J3 : Evolution of Synthetic Strategies to a Streamlined Process.

The total synthesis of Δ(12) -prostaglandin J3 (Δ(12) -PGJ3 , 1), a reported leukemia stem cell ablator, through a number of strategies and tactics is described. The signature cross-conjugated dienone structural motif of 1 was forged by an aldol reaction/dehydration sequence from key building blocks enone 13 and aldehyde 14, whose lone stereocenters were generated by an asymmetric Tsuji-Trost reaction and an asymmetric Mukaiyama aldol reaction, respectively. During this program, a substituent-governed regioselectivity pattern for the Rh-catalyzed C-H functionalization of cyclopentenes and related olefins was discovered.

Synthesis and Biological Investigation of Δ(12)-Prostaglandin J3 (Δ(12)-PGJ3) Analogues and Related Compounds.

A series of Δ(12)-prostaglandin J3 (Δ(12)-PGJ3) analogues and derivatives were synthesized employing an array of synthetic strategies developed specifically to render them readily available for biological investigations. The synthesized compounds were evaluated for their cytotoxicity against a number of cancer cell lines, revealing nanomolar potencies for a number of them against certain cancer cell lines. Four analogues (2, 11, 21, and 27) demonstrated inhibition of nuclear export through a covalent addition at Cys528 of the export receptor Crm1.

Synthesis and biological evaluation of dimeric furanoid macroheterocycles: discovery of new anticancer agents.

A recently developed dimerization/macrocyclization was employed to synthesize a series of macroheterocycles which were biologically evaluated, leading to the discovery of a number of potent cytotoxic agents (e.g., 27: GI50 = 51 nM against leukemia CCRF-CEM cell line; 29: GI50 = 99 nM against melanoma MDA-MB-435 cell line).

Total synthesis of viridicatumtoxin B and analogues thereof: strategy evolution, structural revision, and biological evaluation.

The details of the total synthesis of viridicatumtoxin B (1) are described. Initial synthetic strategies toward this intriguing tetracycline antibiotic resulted in the development of key alkylation and Lewis acid-mediated spirocyclization reactions to form the hindered EF spirojunction, as well as Michael-Dieckmann reactions to set the A and C rings. The use of an aromatic A-ring substrate, however, was found to be unsuitable for the introduction of the requisite hydroxyl groups at carbons 4a and 12a.

Total synthesis of Δ¹²-prostaglandin J₃, a highly potent and selective antileukemic agent.

A catalytic asymmetric total synthesis of the potent and selective antileukemic Δ(12)-prostaglandin J3 (Δ(12)-PGJ3) is described. The convergent synthesis proceeded through intermediates 2 and 3, formed enantioselectively from readily available starting materials and coupled through an aldol reaction followed by dehydration to afford stereoselectively the cyclopentenone alkylidene structural motif of the molecule.

Total synthesis and structural revision of viridicatumtoxin B.

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Will The Real Viridicatumtoxin B Please Stand Up: Total synthesis of viridicatumtoxin B resulted in its structural revision and opens the way for analogue construction and biological evaluation of this complex tetracycline antibiotic. The highly convergent strategy employed allows for swift construction of the entire carbocyclic framework of the molecule.

Constructing molecular complexity and diversity: total synthesis of natural products of biological and medicinal importance.

The advent of organic synthesis and the understanding of the molecule as they occurred in the nineteenth century and were refined in the twentieth century constitute two of the most profound scientific developments of all time. These discoveries set in motion a revolution that shaped the landscape of the molecular sciences and changed the world. Organic synthesis played a major role in this revolution through its ability to construct the molecules of the living world and others like them whose primary element is carbon.

A total synthesis trilogy: calicheamicin γ1(I), Taxol®, and brevetoxin A.

Detailed behind-the-scenes accounts of the total syntheses of calicheamicin γ(1)(I), Taxol(®), and brevetoxin A are discussed with particular emphasis placed on strategies and tactics employed in these campaigns.

An expedient synthesis of a functionalized core structure of bielschowskysin.

A five-step synthesis of a functionalized tricyclo[9.3.0.

Long-range shielding effects in the (1)H NMR spectra of Mosher-like ester derivatives.

The relative magnitudes of the chemical shift differences (Deltadeltas) in the two diastereomers of menthyl esters of known chiral derivatizing agents (CDAs) were compared to those of the alpha-methoxy-alpha-trifluoromethyl-1-naphthylacetyl (MTN((1))A) analogues I. Discrimination of the terminal diastereotopic methyl resonances in esters of the homologous, symmetrical carbinols II was evaluated. Remarkably, the methyls differed in the MTN((1))A esters III even when n = 15; an unexpected crossover in the sign of the Deltadelta values was also observed.

An expedient procedure for the oxidative cleavage of olefinic bonds with PhI(OAc)2, NMO, and catalytic OsO4.

PhI(OAc)(2) in the presence of OsO(4) (cat.) and 2,6-lutidine cleaves olefinic bonds to yield the corresponding carbonyl compounds, albeit, in some cases, with alpha-hydroxy ketones as byproduct. A more practical and clean protocol to effect oxidative cleavage of olefinic bonds involves NMO, OsO(4) (cat.