Carbamoyl group

Figure 11.3 Biosynthetic origin of the O-methyl and carbamoyl groups of mitomycin C.

Note The A-substituent may be varied considerably for example, the amino group may be part of a carbamoyl group. 

Note Several complicated but interesting examples of this cyclization have been reported all involve loss of a substituted-amino portion of the carbamoyl grouping. 

Similarly, a carbamoyl group can be introduced by the use of the radicals H2N—C or Mc2N—C- generated from formamide or DMF and H2SO4, H2O2, and... 

L-Ornithine transcarbamoylase catalyzes transfer of the carbamoyl group of carbamoyl phosphate to ornithine, forming citrulline and orthophosphate (reaction 2, Figure 29-9). While the reaction occurs in the mitochondrial matrix, both the formation of ornithine and the subsequent metabolism of citmlline take place in the cytosol. Entry of ornithine into mitochondria... 

Enantiomers were generated and tumbled at specific angles around each NH proton and the C=0 oxygen at the 2-, 3-, and 6-positions of the carbamoyl group of 23a and 23x, which are considered to be the most important adsorbing sites from chromatographic resolution and NMR studies,... 

The present procedure provides a convenient method for the generation of carbamoyllithiums from carbamoyl halides and is very useful synthetically for the introduction of carbamoyl groups into organic molecules. 

The carbamoyl group is transferred to the serine hydroxyl in the enzyme, but the resultant carbamoyl-enzyme intermediate then hydrolyses only very slowly (minutes rather than microseconds), effectively blocking the active site for most of the time. The slower rate of hydrolysis of the serine carbamate ester is a consequence of decreased carbonyl character resulting from resonance stabilization, as shown. 

Lithiated alkyl carbamates [e.g. 44 from 32a (Cb for Cby)] decompose above —40°C with migration of the carbamoyl group to produce a-hydroxy carboxamides 45 (equation 8) . ... 

An interesting chain elongation of 4-oxo-l-tributylstannylbutyl carbamate 83 by ethynyl A,A-diisopropyl carbamate (82) to the dicarbamate 84 and the subsequent intramolecular carbolithiation to form the alkenyllithium 86 has been reported very recently (equation 18). 86 was trapped by electrophiles to yield—as expected—both epimers 87 and 88 in essentially equal amounts. From an X-ray analysis of a derivative, the shown absolute configuration and the ( )-stereochemistiy at the double bond was concluded. Thus, the attack at the triple bond here took place in the anti fashion, which is quite unusual. We suggest that a lithium cation in 85, captured by the second carbamoyl group, catalyses the anti addition. ... 

The generation of a nitrile oxide bearing a carbamoyl group (i.e., 16) was effected by treating 4-nitro-3-isoxazoline-5-one (15) with a mixture of acetonitrile and water (Scheme 6.5). Although the mechanism of this reaction is not clear, the method allows for the formation of a functionalized nitrile oxide (16) and subsequent cycloaddition under mild conditions (91). 

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