Hydrogenolytic conditions

TaniaPhos active catalyst discussion As shown by Salzer (2) such complexes with half sandwich stracture result in the catalyst cycle into a hydride species where the pentadienyl moiety can be hydrogenolyticaUy liberated (2, 6). This was verified in the case of BINAP complexes (2, diss. Podewils, Geyser). In accordance to this fact and other mechanistic aspects from Noyori s work (3, 5) it is likely that the pre-catalyst species undergoes the same reaction pathway and that the reactive part of the pre-catalyst, the pentadienyl moiety, will be liberated under hydrogenolytic conditions as shown below in Scheme 23.9 ... 

Conversion of the iV -PhFl into the iV -Boc Derivative in 2-[0-Benzyl-A-(9-phenyl-9-fluorenyl)-D-serinyl]isoxazoKdine (122) under Hydrogenolytic Conditions Typical Procedure (Scheme 58) ... 

Amidation of 203 followed by partial hydrolysis affords D-jS-malamic acid (899). Reduction of 899 with diborane furnishes (R)-4-amino-l,2-butanediol (900). Protection of the amine with a Cbz group and conversion of the primary alcohol to a bromide leads to the critical intermediate 901. Alkylation of lysine derivative 902 with 901 and removal of the protecting groups under hydrogenolytic conditions gives hypusine (903). 

The selective cleavage of carbon-carbon bonds in sugars can be achieved under relatively mild hydrogenolytic conditions using a ruthenium complex catalyst thus, besides D-mannitol and D-glucitol, D-fructose yielded up to 30% of glycerol. ... 

The 2-deoxy-derivative was obtained from the known 2,6-dideoxy-L-arahi/to-hexono-l,4-lactone, while the 4-deoxy-derivative was obtained by radical reduction of an O-protected L-ifaamnose 4-xanthate derivative. The 3-deoxy-derivative (42) was obtained from L-rhamnose via a mixture of acetylated L-rhamnono-1,4-lactone (41) and its 1,5-lactone istnner, utilizing hydrogenolytic conditions that effect elimination of acetic acid and stereoselective reduction of the resulting 3-deoxy-hex-2-enonolactone (Scheme 7). 2- and 4-Deoxy-L-rhamnose exist mainly in the pyranose form in solution, whereas 3-deoxy-L-ifaamnose (38) forms a mixture of pyranose and furanose forms in the ratio 2 1. Similar reactions have been used to convert benzoylated... 

Prenyl groups are acid sensitive and are not compatible with hydrogenolytic conditions. This influences the choice of the protecting groups for the amino acids that consequently need to be removed under basic or mild acidic conditions. The same limitation concerns the solid support to be used. 

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