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It has been established that dihalodiphosphinenickel(II) complexes exhibit extremely high catalytic activity for selective cross-coupling of Grignard reagents with aryl and alkenyl halides. This catalytic reaction can be employed in synthetic practice for reasons of simple procedures, mild reaction conditions, high yields and high purity of the coupling products, and the wide applicability to reactions involving primary and secondary alkyl (regardless of the presence or absence of β-hydrogen (s)), aryl, and alkenyl Grignard reagents and nonfused, fused, and substituted aromatic halides and haloolefins. Limitations lie in sluggish reactions between alkyl Grignard reagents and dihaloethylenes. The most effective catalysts are [Ni{(C6H5)2P(CH2)3P(C6H5)2}Cl2] for alkyl and simple aryl Grignard reagents, [Ni{(CH3)2P(CH2)2P(CH3)2}Cl2] for alkenyl and allylic Grignard reagents and [Ni{P(C6H5)3}2-Cl2] for sterically hindered aryl Grignard reagents and halides. Great stabilizing effects of phosphine ligands on the catalytic species are demonstrated by no effect observed after aging the catalyst. Organic chlorides are generally the most suitable halide in view of the reasonable reactivities and limited side reactions. Ether is favored over tetrahydrofuran as solvent. About sixty experimental results are presented and several features are discussed.

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The proteinase responsible for bone collagen degradation in osteo-resorption was examined. The bone pit formation induced by parathyroid hormone (PTH) was markedly suppressed by leupeptin, E-64 and cystatin A, while no inhibition was observed by CA-074, a specific inhibitor of cathepsin B. Pig leucocyte cysteine proteinase inhibitor (PLCPI), a specific inhibitor of cathepsin L, and chymostatin, a selective inhibitor of cathepsin L, completely inhibited the pit formation. Cathepsin L activity in osteoclasts was much higher than the other cathepsin activities. Serum calcium in rats placed on a low calcium diet was decreased by treatment of E-64 or cystatin A, but not by CA-074. These findings suggest that cathepsin L is the main proteinase responsible for bone collagen degradation.

Secretion of procathepsin L into the culture medium from a bone cell mixture was markedly enhanced by addition of parathyroid hormone (PTH), 1 a,25-(OH)2D 3 or tumor necrosis factor a (TNFa). These stimulators of secretion of procathepsin L enhanced bone pit formation, which was inhibited by E-64, but not by CA-074, a specific inhibitor of cathepsin B. Procathepsin L may thus participate in the process of bone collagenolysis during bone resorption. Procathepsin L partially purified from rat long bones under cold conditions was rapidly converted to the mature form under acidic conditions at room temperature. This conversion was inhibited by E-64, suggesting that the procathepsin L secreted into lacunae is catalytically converted to the mature enzyme by cysteine proteinase(s).In the present study, designed to clarify the mechanism and regulation of both the secretion of procathepsin L and its processing in lacunae, we examined the secretion of procathepsin L induced by 10~,25-(OH)2D 3, TNFc~ or by PTH, and also the effects of the cysteine proteinase inhibitors, E-64 and CA-074, on the pit formation induced by these effectors. Furthermore, to clarify the participation of cysteine proteinase(s) in processing from the precursor to the active form, the inhibitory effect of E-64 on the processing of procathepsin L partially purified from rat long bones was also examined. Experimental