R-butoxycarbonyl

Kaiser and Muchowski (41) reduced A -(r-butoxycarbonyl) pyrroles to the corresponding pyrrolidines over 5% Pt-on-C at room temperature and atmospheric pressure. Under these conditions 0-benzyl groups are retained and 2,5-disubstituted pyrroles are reduced mainly or exclusively to thecis-2,5-disubstituted pyrrolidines. In some cases Pt-on-C proved superior to either Rh-on-C or PtO,. 

The t-butoxycarbonyl (rBoc) group is another valuable amino-protecting group. The removal in this case is done with an acid such as trifluoroacetic acid or /Moluenesulfonic acid.218 r-Butoxycarbonyl groups are introduced by reaction of amines with f-butoxypyrocarbonate or a mixed carbonate-imidate ester known as BOC-ON. 219... 

Abbreviated name for = Li derivative LiBTOC (A -lithio r-butyl iV-(tosyloxy) carbamate [N-lithio iV-(r-butoxycarbonyl) 0-tosylhydroxylamine]. 

If the lithiated dihydropyridine contains a removable substituent on the nitrogen and if subsequent removal of the substituent is accompanied by oxidation then substituted pyridines can be obtained [88AHC(44)-199]. Thus, pyridine can be converted to a l-(t< r/-butoxycarbonyl)-... 

AMINO ACIDS 2-r-Butoxycarbonyl-oxyimino-2-phenylacetonitrile. Palladium catalysts. Thioanisole-Trifluoro-aeetic acid. 

ASYMMETRIC HYDROGENATION (2R, 4R) and (2S, 4S)-N-Acryloyl-4-(diphenylphosphine)2-[(diphenylphosphine)methyl]pyrrolidine. (2S, 4S)-N-(r-Butoxycarbonyl)-4-(diphenylphosphine)-2-[(diphenylphosphine)methyl]pyrrolidine. Ferrocenylphosphines, chiral. ASYMMETRIC PHENYLTHIOLATION Quinine. 

More stable JV-acylpyridinium salts can be formed by using 4-(JV,JV-dialkyl-amino)pyridines. The salts are less readily hydrolyzed and are effective in the acylation of sterically hindered alcohols (72S619) and in the formation of N-r-butoxycarbonyl derivatives of a-amino acids in aqueous alkali, for use in peptide synthesis (71CC267). 

Cleavage of carbamates. N-Benzyloxy- and N-r-butoxycarbonyl protected peptide derivatives can be selectively cleaved by reaction with ISilCHsls at 25-50° in the presence of side-chain blocking groups such as methyl esters or benzyl ethers. 

Protection of amino groups. The reagent (I) reacts with amino acid esters to give N-r-butoxycarbonyl (/-BOC) derivatives (2) in good yield. In a typical procedure glycine ethyl ester hydrochloride is suspended in chloroform and NaHCOj in water... 

Figure 1 Rates of Guanidinylation of Benzylamine with iV -Bis(tert-butoxycarbonyl)-S-methylisothiourea ( ), iV,iV -Bis(te/r-butoxycarbonyl)pyrazole-l-carboximidamide ( ), Ai,Ai -Bis(tert-butoxycarbonyl)thiourea in the Presence of the Mukaiyama Reagent ( ), and l,3-Bis(tert-butoxycarbonyl)-2-triflylguanidine ( )...

The sodium salt of diethyl N-(r-butoxycarbonyl)phosphoramidate (98) reacted with alkyl halides in boiling benzene in the presence of tetrabutylammonium bromide to give the corresponding N-alkyl derivatives (99) in 71-95% yields for primary alkyl halides and 38-58% yields for secondary a-halo esters (in MeCN). The phosphoryl and r-butoxycarbonyl groups were removed by treatment overnight with benzene saturated with dry HCl (Scheme 41). ... 

Preparation of a-amino acid amides of aromatic amines (111) is easily conducted as a one-pot procedure by the modified Curtius reaction of aromatic carboxylic acids with DPPA, followed by reaction with iV-protected a-amino acids (equation 44). By this method, -t-butoxycarbonyl-L-leucine p-nitroanilide, which serves as a substrate for leucine aminopeptidase after deblocking of its r-butoxycar-bonyl group, has been efficiently prepared from p-nitrobenzoic acid and -r-butoxycarbonyl-L-leucine. 

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