Synthesis of (+)-vinblastine and its analogues

A synthetic route to vinblastine and its analogues with an ethynyl group, which features a stereoselective coupling of an 11-membered key intermediate with vindoline, is described. Transformations of the alkynyl moiety including a partial reduction as well as a Sonogashira coupling furnished a variety of analogues.

Total synthesis of (+)-yatakemycin

A convergent total synthesis of (+)-yatakemycin was accomplished in a 20-step sequence in an overall yield of 13%. The synthesis features the regioselective ring opening of (S)-epichlorohydrin with 2,6-dibromophenyllithium species, the mild copper-mediated aryl amination utilizing the combination of CuI and CsOAc, and the efficient deprotection of benzyl groups of aryl benzyl ether with BCl3 in the presence of pentamethylbenzene.

Novel Structural Motifs Consisting of Chiral Thiazolines: Synthesis, Molecular Recognition, and Anticancer Activity

The facile synthesis of linear and cyclic chiral oligo(4-alpha/beta-methyl)thiazolines is described. Linear oligothiazolines have been efficiently synthesized by the iterative formation of thiazoline rings and two-directional block condensation. The construction of 24- to 36-membered cyclic oligothiazolines was achieved through the head-to-tail cyclo-oligomerization of doubly deprotected linear fragments. Studies of the interactions of both the linear and cyclic oligomers with chiral compounds revealed that cyclic oligomers displayed a strong binding affinity towards mandelic acid, whereas linear oligomers showed a poor affinity. Linear oligomers have been proven to inhibit the cell growth of the cancer cell lines HPAC, PC-3, and HCT-116. Studies of the structure-activity relationships showed that the IC50 values are clearly dependent on both the length and the terminal functionalities of the linear oligomers. Longer derivatives showed more potent activity (e.g., hexi- and octithiazolines exhibit IC50<1 microM) against all three cancer cell lines. In sharp contrast, cyclic oligomers were inactive to all three cell lines.

Stereocontrolled total synthesis of (-)-kainic acid

[reaction: see text] A stereocontrolled total synthesis of (-)-kainic acid is described. A fully functionalized trisubstituted pyrrolidine ring was constructed by ring-closing metathesis of an acrylate derivative followed by an intramolecular Michael addition of the resultant alpha,beta-unsaturated lactone with high diastereoselectivity. Two alternative protocols for the construction of the alpha,beta-unsaturated lactone were also developed.

Design and synthesis of thiazoline–thiazole hybrid macrocycles possessing strong binding affinity to Pb2+ and Cd2+

Thiazoline-thiazole hybrid macrocycles were synthesized via head-to-tail cyclooligomerization. The macrocycle consisting of eight heterocyclic subunits displays high binding affinity to the heavy metal toxins Pb(2+) and Cd(2+).

Synthesis of chiral cyclic oligothiazolines: a novel structural motif for a macrocyclic molecule

The synthesis of chiral cyclic oligo(4-beta-methyl)thiazolines is described; linear oligothiazolines were efficiently prepared by the iterative formation of a thiazoline ring and a two-directional block condensation, and construction of 24- to 36-membered cyclic oligothiazoline systems could be achieved by the head-to-tail cyclooligomerization of doubly deprotected linear fragments and subsequent thiazoline formation.

Stereocontrolled Total Synthesis of (−)-Eudistomin C

A stereocontrolled total synthesis of (-)-eudistomin C was accomplished in 18-step sequence with an overall yield of 7.7%. The synthesis features the diastereoselective Pictet-Spengler reaction of a tryptamine derivative and the Garner aldehyde catalyzed by Bronsted acids, and the unprecedented construction of the unusual oxathiazepine ring by intramolecular alkylation.

Stereocontrolled Total Synthesis of (−)-Kainic Acid. Regio- and Stereoselective Lithiation of Pyrrolidine Ring with the (+)-Sparteine Surrogate

[reaction: see text] A stereocontrolled total synthesis of (-)-kainic acid is described. cis-3,4-Disubstituted pyrrolidine ring was constructed by [3 + 2] cycloaddition of azomethine ylide with chiral butenolide. The crucial introduction of carboxyl group at the C-2 position was executed by regio- and stereoselective lithiation of the pyrrolidine ring in the presence of a (+)-sparteine surrogate followed by trapping with carbon dioxide.

Fluorescence enhancement by hydroperoxides based on a change in the intramolecular charge transfer character of benzofurazan

Strong fluorescence signals were observed after the reaction of novel reagents with hydroperoxides.

Thermal and Palladium-Catalyzed [3 + 2] Synthesis of Cyclopentadienone Acetals from Cyclopropenone Acetals and Acetylenes

[reaction: see text] Substituted cyclopentadienone acetals (CPDAs) were synthesized by a thermal or palladium-catalyzed [3 + 2] cycloaddition reaction of a substituted cyclopropenone acetal to an electron-deficient acetylene. The synthesis afforded di-, tri-, and tetra-substituted CPDAs of considerable structural varieties that undergo Diels-Alder reaction to produce bicyclo[2.2.1]heptenes.

Stereocontrolled total synthesis of (+)-vincristine

An efficient total synthesis of (+)-vincristine has been accomplished through a stereoselective coupling of demethylvindoline and the eleven-membered carbomethoxyverbanamine presursor. Demethylvindoline was prepared by oxidation of 17-hydroxy-11-methoxytabersonine, followed by regioselective acetylation with mixed anhydride method. Although an initial attempt of coupling by using demethylvindoline formamide was not successful and resulted in recovery of the starting compounds, the reaction using demethylvindoline took place smoothly to furnish the desired bisindole product with the correct stereochemistry at C18'. After formation of the piperidine ring by sequential removal of the protective groups and intramolecular nucleophilic cyclization, the total synthesis of vincristine was completed by formylation of N1.

Total Synthesis of (−)-Strychnine

Total synthesis of (-)-strychnine is described. Notable features of our synthesis include (1) palladium-catalyzed coupling of the indole and vinyl epoxide moieties, (2) synthesis of the nine-membered cyclic amine derivative from the diol precursor in a one-pot procedure, and (3) transannular cyclization of the nine-membered cyclic amine.