Alice Kanazawa

Improved preparation of angelate esters

Abstract A new procedure has been developed for the efficient preparation of angelate esters from alcohols. The alcohol is treated in dry toluene at 70–80 °C for 19–36 h with a mixed anhydride prepared from angelic acid and 2,4,6-trichlorobenzoyl chloride. In the absence of base, no tiglate ester is produced.

Efficient, large-scale preparation of (R)- and (S)-1-(2,4,6-triisopropylphenyl)ethanol, versatile chiral auxiliary for cyclopentenone, γ-butyrolactone, and γ-butyrolactam synthesis

Abstract A particularly efficacious, low-cost preparation of both ( R )- and ( S )-triisopropylphenyl)- ethanol , useful chiral controllers in the dichloroketene—enol ether cycloaddition reaction, has been developed.

Novel, efficient total synthesis of natural 20(S)-camptothecin

Enantiopure 20(S)-camptothecin has been prepared from a known hydroxypyridone through a novel approach that involves a Claisen rearrangement, an asymmetric nucleophilic ethylation, a Heck coupling and a Friedländer condensation as the key transformations.

Synthesis of (R)-(−) and (S)-(+)-3-(1-pyrrolyl)propyl- N-(3,5-dinitrobenzoyl)-α-phenylglycinate and derivatives. A suitable chiral polymeric phase precursor

Abstract A synthetic route to obtain ( R )-(−) ( 1 ), ( S )-(+)-3-(1-pyrrolyl)propyl- N -(3,5-dinitrobenzoyl)-α-phenylglycinate ( 2 ) and derivatives is described. In a first step, pyrrole derivatives were prepared using the Clauson-Kaas method. The esterification, second step, was performed using basic conditions due to sensitivity of the pyrrole group toward acidic conditions. A tautomeric equilibrium involving the stereogenic center induces the product epimerization. The substitution of DMAP and Et 3 N by a highly hindered base, proton-sponge ® , furnished the final products without racemization. The ee of 1 , 2 and of the corresponding methyl esters ( 3 and 4 ) were determined by 1 H NMR analysis in the presence of optically active Eu(tfc) 3 . Epimerization was not observed in the preparation of the carboxylate salts ( 5 – 8 ).

Synthesis and bioevaluation of 22-hydroxyacuminatine analogs

A series of 22-hydroxyacuminatine analogs was prepared by using different Friedländer condensations. Several of the new compounds were tested for antiproliferative activity on cancer cell lines and for topoisomerase I inhibitory activity.

Concise synthesis of 22-hydroxyacuminatine, cytotoxic camptothecinoid from Camptotheca acuminata, by pyridone benzannulation.

A short, efficient synthesis of 22-hydroxyacuminatine, starting from a readily accessible hydroxy pyridone, is presented; key steps include a Heck coupling with methyl pentadienoate, a flash vacuum pyrolytic cyclization, and a Friedländer condensation.

Stereoselective synthesis of (-)-homogynolide-A

Abstract (−)-Homogynolide-A, a spiro β-methylene-γ-butyrolactone sesquiterpene from Homogyne alpina , has been stereoselectivity prepared in natural form from S -(+)-carvone.

Stereoselective synthesis of homogynolide-A, A bakkane from homogyne alpina

Abstract Homogynolide-A, an antifeedant sesquiterpene, has been stereoselectively prepared from benzoquinone.

Transition-metal-catalyzed ring expansion of diazocarbonylated cyclic N-hydroxylamines: a new approach to cyclic ketonitrones.

Novel C-ethoxycarbonyl cyclic ketonitrones are synthesized from the Ag- or Cu-catalyzed ring expansion of β-diazo cyclic hydroxylamines. The latter are themselves easily obtained by the addition of lithiated ethyl diazoacetate onto cyclic nitrones. The regioselective metal-catalyzed rearrangement of β-diazo cyclic hydroxylamines proved highly efficient and resulted in a synthetically useful ring expansion to produce 6- or 7-membered ring functionalized nitrones. The outcome of the two steps, i.e. nucleophilic addition of α-diazoesters to nitrones and ring expansion, is a formal nitrone homologation.

Direct, stereoselective synthesis of the protected paclitaxel (taxol) side chain and high-yield transformation to paclitaxel

A short, efficient approach to the p-methoxybenzylidene-protected paclitaxel (Taxol) side chain through benzaldehyde benzoylimine-chiral enolate condensation, followed by DDQ-mediated oxazolidine formation and hydrolysis is described; the C-7-triethylsilyl derivative of baccatin III undergoes esterification with this side chain in the presence of DCC and DMAP to provide after acid hydrolysis paclitaxel in excellent overall yield.