New methods for β-conjugate addition and β-hydroxyalkylation of enones

Enantioselective Total Synthesis of (-)-Hunterine A Enabled by a Desymmetrization/Rearrangement Strategy

The first enantioselective total synthesis of (-)-hunterine A is disclosed. Our strategy employs a catalytic asymmetric desymmetrization of a symmetrical diketone and subsequent Beckmann rearrangement to construct a 5,6-α-aminoketone. A convergent 1,2-addition joins a vinyl dianion nucleophile and the enantioenriched ketone. The endgame of the synthesis features an aza-Cope/Mannich reaction and azide-olefin dipolar cycloaddition to complete the pentacyclic ring system. The synthesis is completed through a regioselective aziridine ring opening.

Development of New Innovative Synthetic Organic Chemistry Using Lone Pairs of Oxygen Atoms

Oxygen atoms have a lone pair of electrons, so they have high chelation ability, high nucleophilic ability, stabilizing ability of adjacent cations, and take a chelate or oxocarbenium ion structure with Lewis acids and metals. I took advantage of these properties to develop three new reactions, 1) asymmetric synthesis of chiral quaternary carbon centers, 2) asymmetric synthesis using acetal functions, and 3) organic chemistry using acetal-type reactive salt chemical species, and applied them to biologically active natural products synthesis. New reactions described here are all innovative and useful for natural products synthesis. In particular, the first asymmetric synthesis of fredericamycin A, and concise asymmetric synthesis of anthracycline antibiotics, scyphostatin, (+)-Sch 642305, (-)-stenine, clavolonine, (+)-rubrenolide, (+)-rubrynolide, (+)-centrolobine, and decytospolide A and B, etc., are noteworthy. Furthermore, since reactions using acetal-type reactive salt chemical species allow the coexistence of functional groups that normally cannot coexist, the reactions using reactive salts have potential to change the retrosynthesis planned based on conventional reactions.

Indium-mediated beta-allylation, beta-propargylation, and beta-allenylation onto alpha,beta-unsaturated ketones: reactions of in-situ-generated 3-tert-butyldimethylsilyloxyalk-2-enylsulfonium salts with in-situ-generated organoindium reagents

3-tert-Butyldimethylsilyloxyalk-2-enylsulfonium salts, generated in situ from the reaction of alpha,beta-enones with dimethyl sulfide in the presence of TBSOTf, underwent a novel nucleophilic substitution with allylindiums to give silyl enol ethers of delta,epsilon-alkenyl ketones in good yields, which correspond to formal Michael addition products. In a similar manner, 1,4-propargylation of propargylindiums onto the sulfonium salts produced the corresponding silyl enol ethers of delta,epsilon-alkynyl ketones in good yields. Organoindium reagents derived from gamma-substituted propargyl bromide and indium afforded the corresponding silyl enol ethers of beta-allenyl ketones in good yields. The reaction proceeds via an addition-substitution mechanism involving the formation of allylic sulfonium salts. The presence of the intermediate sulfonium salt was confirmed by observation of the low-temperature (1)H NMR spectra.

Highly efficient 1,4-addition of 1,3-diesters to conjugated enones by In/TMSCl

Organoindium reagents derived from indium and diethyl bromomalonates were added to a wide range of conjugated enones in a 1,4-fashion in the presence of TMSCl under mild conditions, and corresponding oxo-1,3-diesters were obtained in good to excellent yields.

Novel phosphine-catalyzed zipper cyclization of aliphatic diyne-dione and yne-dione systems

[reaction: see text] An unexpected tri-n-butylphosphine-catalyzed zipper cyclization of diyne[bond]diones (1a-d) or yne-diones (1e and 1f) is described. Bicyclic ketones (2a, 2b, 2c, 2e, and 2f) with five- or six-membered rings fused to the five-membered ring were obtained from both aliphatic diyne-diones (1a-c) and yne-diones (1e and 1f) having tetra- or pentamethylene spacers. The bicyclic products (2) were produced with high diastereoselectivity.

A novel nucleophilic substitution of in situ generated 3-tert-butyldimethyl- silyloxyalk-2-enylsulfonium salts with allylindium reagents

[reaction: see text] In situ generated 3-tert-butyldimethylsilyloxyalk-2-enylsulfonium salts derived from the reaction of alpha,beta-enones with dimethyl sulfide in the presence of TBSOTf undergo a novel nucleophilic substitution with in situ generated allylindium reagents from indium and allyl halides to give silyl enol ethers of delta,epsilon-unsaturated ketones, which correspond to Michael addition products, in good yields.