Carbamate substrate

A solution of fuming or absolute nitric acid in acetic anhydride is another commonly used reagent for the V-nitration of V-alkylamides. Curry and Mason used this reagent to synthesize a series of aliphatic and alicyclic V-nitro-V-alkylcarbamates from the corresponding V-alkylcarbamates. Aromatic ring nitration is observed if aryl groups are present in the carbamate substrate. 

Scheme 37a illustrates a carbamate substrate that has three possible sites for deprotonation the benzylic sites a to either nitrogen or oxygen and the methylene attached to nitrogen. Of these three, the site least likely to deprotonate is the latter. Scheme 37b shows that this organolithinm, inaccessible by deprotonation, can be made readily by tin-lithium exchange. The derived organolithinm compound can be added to electrophiles snch as cyclohexanone in good yields. 

Buchwald later showed that the same reaction could be more efficiently accomplished using a MOP (25)/Pd-catalyst [143]. In addition, the 25/Pd-protocol allowed for the analogous cyclizations to be conducted with carbamate substrates. 

Carbamates such as carbachol are also able to serve i substrates for AChE. forming a catbamylated enzyme iffiii mediate (E-C). The rate of carbamylation (k ) is slo enlL the rate of acetylation. Hydrolysis (kv. decatbamylaliec of the carbaniyl-cnzyme intermediate is 10 times sloar than that of its acetyl counterpart. The slower hyMi rate limits the optimal functional capacity of AChE allw ing carbamate substrates to be semircversible inhibiton i AChE. 

Vinylogous Carbamate Substrates 4.2.1 Acyclic Enamino Esters... 

The carboxylate cross-coupling was further extended to aryl carbamate substrates. Early examples of carbamates as electrophilic coupling partners were reported by Kocienski and Dixon (enol carbamates) [42,43] and Snieckus (aryl carbamates) [44] around 1990 using Grignard reagents. In 2009 Nakamura developed a unique... 

Carbamates. Lower alkyl A/-halo- and W,W-dihalocarbamates are distillable Hquids (70,112). A/-Halo-A/-metallocarbamates are crystalline hygroscopic soHds. A/-Chloro-A/-sodiourethane [17510-52-0] C2H OCONQNa, does not decompose on heating to 250°C (113), but violent decompositions have occurred at room temperature (114). A/-Halocarbamates react with a variety of organic substrates, eg, the free-radical addition of W-chlorourethane [16844-21 -6] C2H OCONHCl, and A,A-dichlorourethane [15698-16-5], C2H OCONCl2, to olefins provides a convenient route to... 

Phenethyl carbamate derivatives 30 have also been employed in Bischler-Napieralski reactions cyclization of these substrates affords 3,4-dihydroisoquinolones 31. These reactions have been conducted using a variety of different promoters including PPA, POCl3, and Tf20. Mixtures of P2O5 and POCI3 appear to afford the best results in some cases. 

Substitution on the phenethyl side chain of the substrate is usually well tolerated. For example, reaction of carbamate 44 with POCI3 afforded a 75% yield of the corresponding lactam 45. However, in some instances substituents on the chain lead to low yields, such as in the reaction of amide 46, which provided only a 29% yield of the desired product 47 (albeit with 9 1 diastereoselectivity). ... 

Cuprates react rapidly witli allylic halides for acetates) [17, 23], propargyl halides for acetates) [ 106-108], and vinyloxiraties, often witli S 2 regioselectivity iSclieme 10.9) [17]. Hie reaction takes place witli emit stereodieniistry iwitli respect to tlie leaving group), while syn substitution occurs when an allylic carbamate is employed as tlie substrate [109]. 

In this scheme, EOH is the enzyme, IX is the inhibitor (either a carbamate or an organophosphate). EOH(IX) is analogous to the Michaelis Menton comploc seen with the substrate reaction. EOI is the acyl-enzyme intermediate for carbamates or a phosphoro-enzyme intermediate for the organophosphates. The equilibrium constant for this reaction (K ) is defined as k /k and the phosphorylation or carbamylation constant is defined as k2- In this study 42)y ANTX-A(S) was found to be more specific for AChE than BUChE. The double reciprocal and Dixon plot of the inhibition of electric eel AChE indicated that the toxin is a non-competitive inhibitor decreases, k remains unchanged) (Figure 2). 

Lippi et. al (87) and Dirstine (88) circumvented titration by converting the liberated fatty acids into copper salts, which after extraction in chloroform are reacted with diethyldithio-carbamate to form a colored complex which is measured photometrically. While the end point appears to be more sensitive than the pH end point determination, the advantages are outweighed by the additional steps of solvent extraction, centrifugation and incomplete extraction when low concentrations of copper salts are present. Other substrates used for the measurement of lipase activity have been tributyrin ( ), phenyl laurate (90), p-nit ro-pheny1-stearate and 3-naphthyl laurate (91). It has been shown that these substrates are hydrolyzed by esterases and thus lack specificity for lipase. Studies on patients with pancreatitis indicate olive oil emulsion is definitely superior to water soluble esters as substrates for measuring serum lipase activity. 

---