[reaction: see text] Racemic homoallylic alcohols have been synthesized by palladium-catalyzed three-component coupling of an arylboronic acid, an allene, and an aldehyde.
The disorazoles comprise a family of 29 closely related macrocyclic polyketides isolated in 1994 from the fermentation broth of the gliding myxobacterium Sorangium cellulosum. Disorazoles A 1 , E and C 1 have shown exceptional biological activities toward inhibiting the proliferation of human cancer cell lines in picomolar and nanomolar concentrations through the disruption of microtubule polymerization. This review gives a brief introduction describing the biosynthesis and the significance of the disorazoles as a new class of microtubulin disruptors. Another portion of the review focuses on the biology of the disorazoles, specifically disorazole A 1 and C 1 , and their antiproliferative efficacy against animal and human tumor cell lines, as well as the available SAR data. The majority of the discussion addresses synthetic efforts, including partial syntheses of various disorazoles and a summary of the total synthesis of disorazole C 1 .
The total synthesis of a bis-cyclopropane analog of the antimitotic natural product (-)-disorazole C1 was accomplished in 23 steps and 1.1% overall yield. A vinyl cyclopropane cross-metathesis reaction generated a key (E)-alkene segment of the target molecule. IC50 determinations of (-)-CP2-disorazole C1 in human colon cancer cell lines indicated low nanomolar cytotoxic properties. Accordingly, this synthetic bioisostere represents the first biologically active disorazole analog not containing a conjugated diene or polyene substructure element.
Wee1
inhibition has received great attention in the past decade
as a promising therapy for cancer treatment. Therefore, a potent and
selective Wee1 inhibitor is highly desirable. Our efforts to make
safer and more efficacious Wee1 inhibitors led to the discovery of
compound 16, a highly selective Wee1 inhibitor with balanced
potency, ADME, and pharmacokinetic properties. The chiral ethyl moiety
of compound 16 provided an unexpected improvement of
Wee1 potency. Compound 16, known as ZN-c3, showed excellent in vivo efficacy and is currently being evaluated in phase
2 clinical trials.
A palladium-catalyzed regioselective bisfunctionalization of allenyl esters with boronic acids (nucleophiles) and aldehydes (electrophiles) was demonstrated. The three-component coupling afforded alpha,beta-unsaturated delta-lactones under mild conditions and with excellent chemo-, regio-, and diastereoselectivity. Aromatic, heteroaromatic and vinylic boronic acids (R1B(OH)2) reacted with ethyl 2,3-butadienoate and benzaldehyde to afford the corresponding 4-R(1),6-Ph-disubstituted alpha,beta-unsaturated delta-lactones in 62-78% yields. Lactones derived from aromatic, heteroaromatic, and vinylic aldehydes were isolated in 51-58% yields, while aliphatic aldehydes were less reactive. The regiochemistry of bisfunctionalization of allenyl ester homologues remained controlled by the ester substituent, and the reactions afforded cis-4,5,6-trisubstituted alpha,beta-unsaturated delta-lactones and esters of (Z)-syn-3,4,5-trisubstituted-5-hydroxy-2-pentenoic acids in combined 47-65% yields. The superior performance of a pi-allylpalladium(II) dimer catalyst featuring an auxiliary allyl ligand derived from beta-pinene, among diverse palladium(II) catalysts, was demonstrated. A catalytic cycle involving an unsymmetrical bis-pi-allylpalladium complex as the key intermediate was proposed, and the communication highlights the synthetic potential of such intermediates. However, the efficiency of asymmetry transfer remained low (<20%).
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