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A novel convergent procedure that has proved useful in the synthesis of a wide range of meroterpenoid-related structures containing a mono-, sesqui, or diterpenoid moiety linked to a nonfused aromatic subunit with various substitution patterns is discussed. The coupling reaction is perfectly compatible with preformed epoxides, while the sequential cyclixation provide exocyclic alkenes.

Research has been conducted on eudesmanolides which are the sequiterpene lactones' main skeletal types. The results of the straightforward synthesis of such eudesmanolides as (+)-3alpha-hydroxyreynosin and (+)-8beta-hydroxyasterolide carried out via different solvents and additives and containing exocyclic double bond are reported.

Research has been conducted on the oxabicyclic compounds. The application of a technique that involves the homolytic opening of epoxides with Ti(III) complexes to acyclic epoxypolyenes is discussed.

The ruthenium complex RuH2(PPh3)4 is an excellent catalyst for the Michael addition of active methylene compounds lacking cyano groups when the reactions are performed in acetonitrile instead of THF. The reaction proceeds satisfactorily in acetonitrile under mild and neutral conditions with malonates, beta-ketoesters, 1,3-diketones, 1,1-disulfones, nitro compounds, Meldrum acid and anthrone as the Michael donors. Cyano acetates can also be ideal substrates for this reaction.

Palladium catalyzes coupling reactions between acid chlorides and E-(1,2)-bis(tri-n-butylstannyl)ethene or beta-stannyl enones to produce butane-1,4-diones. The reaction involves reduction of an enedicarbonyl intermediate. Coupling reactions at low temperatures yield alpha, beta-unsaturated 1,4-diketones, and involve palladium hydride-promoted reduction. This method facilitates synthesis of two 1,4-diketone ipomeanines.

A mild, simple, safe, chemoselective reduction of different kinds of aldehydes to the corresponding alcohols mediated by the Mn dust/water system is described. An efficient, inexpensive alternative for the preparation of the same type of compounds through the synthesis of [alpha]-deuterated alcohols in presence of [D.sub.2]O is also described.

A study was conducted to demonstrate the efficiency of titanocene(III) aqua complexes as a unique class of hydrogen-atom donor (HAT) reagents based on two key features such as excellent binding capabilities of water toward titanocene(III) complexes and a low activation energy for the HAT step. The results provide insight into the remarkable hydrogen-atom donor characteristics of water in [Ti.sup.III]-mediated free-radical chemistry.

Titanocene(III) chemistry is used as indispensible tool in C-C bond-forming reactions and pinacol and related reactions have allowed the steresoselective synthesis of vicinal diols. Smooth reaction conditions are applied for inter- and intramolecular processes and [Cp.sub.2]TiCl is also used as an efficient Lewis acid.

The first Ti-catalyzed Reformatsky-type coupling between [alpha]-halo ketones and aldehydes is described. This reaction has afforded [beta]-hydroxy ketones and the catalytic cycle has proceeded via bis(cyclopentadienyl)titanium enolates.

The synthesis of NaB[(OMe).sub.4] (sodium tetramethoxyborate) by reaction of inexpensive sodium borohydride with methanol is described. The compound possesses an ideal combination of a Lewis base and Lewis acid to catalyze Michael additions of stabilized carbon nucleophiles.

A novel procedure for the straightforward synthesis of seven-membered carbocycles through free-radical chemistry, based on titanocene(III)-catalyzed 7-endo-dig and 7-endo-trig cyclizations is described. This procedure is proved to be useful for the preparation of several natural products including mono-, sesqui-, and diterpenoids with different skeletons containing cycloheptane rings.

A novel strategy for the synthesis of terpenoids with a characteristic gamma-dioxygenated system on the A ring is developed involving three stages. This strategy has proved to be useful for the synthesis of the natural labdane rostratone and related terpenoids, as well as for advanced synthetic approaches toward the pharmacologically active products aphidicolin and pyripyropene A.

The regio- and stereoselectivity of a nickel-promoted allyl/allyl coupling is low. An alternative intramolecular insertion of palladium complexes into alkenes enables efficient synthesis of five or six-membered ring carbocycles. The prospect of effecting the cyclization of substrate II trhough intramolecular palladium-catalyzed cross-coupling of an allylstannane with an allyl acetate is described. The intramolecular reaction resulted in a clean formation of a carbon-carbon bond.