Yuji Naruse

Kinetic resolution of epoxides by chiral organoaluminum catalyst short synthesis of (-)-C16 juvenile hormone

Abstract The use of chiral organoaluminum reagent as a catalyst to resolve simple ketoepoxides is explored. The optically pure ketoepoxide 10 was recovered after 80% conversion. The recovered pure epoxide is a useful chiral building block in the synthesis of chiral terpenes. The method applies for the short asymmetric synthesis of the juvenile hormone by the synthetic route which depends on the palladium-catalyzed coupling process.

A convenient procedure for the regioselective monoprotection of 1,n-diols

Abstract A method is described for regioselective monoprotection of 1,n-diols. The new process depends on regioselective cleavage of orthoester, which is prepared in situ from 1,n-diols and trialkylorthoesters. The produced mono-acetal is useful in subsequent steps as a normal acetal type protecting group.

Organoaluminum reagent as a chemical tool for asymmetrization

Abstract A new process is described for the asymmetrization of meso ketones using organoaluminum reagent.

A new synthetic route to juvenile hormone kinetic resolution of epoxides using organoaluminum reagent

Abstract A short synthetic route to C 16 -juvenile hormone is described which depends on new oxirane ring opening methodology and which also involves the joining of intermediate 8 and 12 in a one flask operation to construct the sesquiterpene structure.

Asymmetrization of meso-cyclic ketones using homochiral acetal templates

Abstract Employing the homochiral acetal template, asymmetrization of meso-substituted cyclohexanones is explored. By the use of optically-active 2,4-pentanediol as a chiral protecting group, highly diastereoselective acetal cleavage is achieved when treated with organoaluminum reagent. Dialkylaluminum amides are also effective reagents for this reaction.

Stereospecific annulation of hydroxy vinyl ethers. Synthetic application to polyfunctionalized cyclic compounds

Abstract Stereospecific annulation of hydroxy vinyl ethers in the presence of triflic anhydride and tertiary amines and its synthetic application are described. Each 1-hydroxy-2-oxabicyclo[n.4.0]alkane, 2-oxabicyclo[n.4.0]alk-1(6)-ene and 2-oxabicyclo[n.4.0]alk-1(6+n)-ene is stereoselectively synthesized from the same hydroxy vinyl ether depending on the choice of the reaction conditions (temperature, solvent and tertiaryamine). These compounds lead to polyfunctionalized cyclic compounds and some natural products. We propose that this annulation reaction proceeds through a pure SN2-like mechanism.

New approach for natural product synthesis using main group organometallic reagents

This paper will review the current state-of-art of organoaluminum- or organoboron-mediated asymmetric reactions in the natural product synthesis. The newly developed methods heavily depend on the characteristic features of main group organometallic compounds. Asymmetric Diels-Alder reaction, pioneered by Walborsky (ref. l), has been established as one of the most important tools in modern synthesis of natural products. In the study of the influence of concave-convex topological features on asymmetric Diels-Alder reactions, a number of fascinating chiral auxiliary groups were reported (ref. 2). However, readily available dimen- thy1 fumarate appears to deserve careful reinvestigations since its primitive topological feature seems to be underestimated. Thus, the Lewis acid coordinated fumarate is considered to exist in the s-trans form predominantly and the two menthyl groups should cooperatively cover the re face of the molecule. A series of dienes was then subjected to Diels-Alder reaction with or- ganoaluminum reagent at low temperature and all the attempted reaction proceeded with excel- lent stereoselection (ref. 3).