Palladium was used in organic synthesis lyzed reactions can be classified into sevfor long time only as a heterogeneous eral groups based on their substrates: catalyst for hydrogenating unsaturated organic halides, allylic compounds, concompounds. But in recent years palladi-jugated dienes, alkenes, and alkynes. um compounds have found broad appli-Propargylic compounds undergo a varication as homogeneous catalysts. In the ety of palladium-catalyzed transformalast decade, homogeneous catalysis rely-tions and make up one important class ing on transition metal complexes has of these reactions. It is well known that led to innovations in organic synthesis. copper and silver salts promote or cataComplexes of various transition metals lyze several reactions of propargylic are now used for organic synthesis, and compounds. However, palladium comeach metal has its own characteristic fea-pounds, particularly Pdo complexes, tures. Palladium complexes are the most show catalytic activities entirely differversatile and used extensively in organic ent from those of silver and copper salts. synthesis, particularly for carbon-carAdvances in the research on the palladibon bond formation. Palladium-cata-um-catalyzed reactions of propargylic compounds in the last decade have made the scope of the reactions clear. The ready availability of numerous propargylic alcohols and their esters by the reaction of terminal alkynes with carbonyl compounds clearly enhances the synthetic utility of their reactions. Palladium complexes, in particular palladium phosphane complexes, are soluble in organic solvents and behave as active catalysts under homogeneous conditions.

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CCN2 is best known as a promoter of chondrocyte differentiation among the CCN family members, and Ccn2 null mutant mice display skeletal dysmorphisms. However, little is known concerning the roles of CCN2 during bone formation. We herein present a comparative analysis of wild-type and Ccn2 null mice to investigate the roles of CCN2 in bone development. Multiple histochemical methods were employed to analyze the effects of CCN2 deletion in vivo, and effects of CCN2 on the osteogenic response were evaluated with the isolated and cultured osteoblasts. As a result, we found a drastic reduction of the osteoblastic phenotype in Ccn2 null mutants. Importantly, addition of exogenous CCN2 promoted every step of osteoblast differentiation and rescued the attenuated activities of the Ccn2 null osteoblasts. These results suggest that CCN2 is required not only for the regulation of cartilage and subsequent events, but also for the normal intramembranous bone development.

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