Carbamic acid esters

In this manner 45 grams of the carbamic acid ester of 1-ethinyl cyclohexanol are obtained. Yield 53% of the theoretical yield. The ester boils at 108° to 110°C/3 mm and on recrystallization from cyclohexane, yields colorless needles melting at 94° to 96°C. 

Beagents for the derivatization of alcohols show variable reactivity and those containing an acid chloride or nitrile group require anhydrous conditions. DMOQ-CONj is the only reagent that reacjts to a significant extent with tertiary alcohols. The product of the reaction is a carbamic acid ester. Detection limits for alcohol derivatives are also frequently nc e than modest... 

The mechanism of the stereoselective syntheses of (K)-3-aryl-5-(hydroxy-methyl)oxazolidinones via the Mannenin reaction of aryl carbamic acid esters with (Jt)-glycidyl butyrate has been explored in detail by Brickner et al. [60]. Namely, N-lithiated carbamate derivatives of anilines are allowed to react with the commercially available (K)-glycidyl butyrate (96-98% enantiomeric excess ee) under appropriate conditions to obtain enantiomerically pure (Jt)-3-aryl-5-(hydroxymethyl)oxazolidinones in 85-99% yields, according the pathways depicted in Scheme 19. 

The potential of carbamic acid ester prodrugs (R-O-CO-NR R") is well-established by a number of studies on their stability and metabolism. Upon hydrolysis, they liberate the active agent ROH and the carbamic acid R R"N-COOH, which, being unstable, breaks down to the amine R R"NH and C02 (see also Sect. 8.7). The mechanism of HCT-catalyzed hydrolysis of carbamates, summarized in Fig. 8.7,b, is more complex than that of carbonates [153][158][159]. In the case of N,N-disubstituted carbamates (R-O-CO-NR R"), the only possible mechanism is as for carbonates (Fig. 8.7,b, Reaction a), which is, presumably, also the mechanism of enzyme-catalyzed hydrolysis for all carbamates. 

Fig. 8.18. Metabolic activation of the prodrug molsidomine (8.159), first by enzymatic hydrolysis of the carbamic acid ester moiety to the inactive metabolite 8.160, followed by spontaneous degradation to the active metabolite 8.161, most likely an NO donor [207] [208]...

I. Christenson, Alkaline Hydrolysis of Some Carbamic Acid Esters , Acta Chem. Scand. 1964, 18, 904-922. 

Carbamate anticholinesterase agents are carbamic acid esters that are hydrolyzed by AChE in a manner similar to that of ACh. Carbamates have this general structure ... 

Reaction of semicarbazides with aryl esters of cyanic acid to give semi-carbamid-carbamic acid esters [80]. 

Molecular structures of four choline esters. Acetylcholine and methacholine are acetic acid esters of choline and -methylcholine, respectively. Carbachol and bethanechol are carbamic acid esters of the same alcohols. 

Carbamic acid and derivs 2 C40—C42 carbamic acid esters 2 C40 carbamic acid ethyl esters 2 C40-C41 carbamic acid methyl ester 2 C41 carbamic azide 2 C40... 

Hydroxyquinoxaline (98) is converted into the 1,4-dioxide (99), and 5-acetamido-7-methylquinoxaline similarly forms the 1,4-dioxide with m-chloroperbenzoic acid in benzene.195a,b 2-Aminoquinoxaline is best oxidized with permaleic acid in ethanol in the presence of sodium bicarbonate. Exclusive 1-oxidation occurs, and the product is conveniently isolated as the carbamic acid ester (100) (85%).115... 

Nathan et al(Ref 1) examined a number of carbamic acid esters and concluded that the best stabilizing action on NC is obtd with compds in which at least one H atom is replaced by an aryl radical. Davis(Refs 2 5) examined several comps for their gelatinizing effect on NC Refs 1)F.L.Nathan et ai, BritP 12743(1912) CA 7, 3842(1913) 2)T.L.Davis, IEC 14, 1140 (1922) 3)Franklin(1935), lllff 4)Sidgewick, OrgChem of N(1937), 272 5)Davis(1943), 322... 

All of these compounds, whether alkylammonium, metal and p-block carbamates, are potential carriers or sources of carbamic groups, and can be used in the synthesis of organic carbamates [6] if the transfer of the RR NC02 moiety to a suitable organic substrate is accomplished [6, 7]. Moreover, alkylammonium, metal and p-block carbamates, as well as carbamic acid esters, are also potential... 

Usually, the traditional routes to the synthesis of carbamic acid esters, isocyanates and ureas start from the toxic compound phosgene [10]. Consequently, the ability to synthesize these compounds from ubiquitous, cheap and safe C02, as an alternative starting material to phosgene, represents an appealing and highly eco-friendly variation to the conventional protocols which have in the past been based on phosgenation. Moreover, it also provides an attractive answer to the current widespread requests for environmental protection [11]. 

Course of the reaction. In Table I, data are presented from two typical experiments which show the relative rates of formation of ammonia and carbon dioxide. These data serve to indicate a possible course of the urea-ethylene glycol reaction. Clearly, the synthesis of ethyleneurea did not proceed through simple elimination of two moles of water from an equimolar mixture of reactants for there was no evidence that water per se was obtained from the reaction. Indeed, it did not appear to be even a primary product since, if it had been and if it had reacted with urea, then the quantity of carbon dioxide relative to ammonia would have been much higher in the early stages of the reaction. From the very large quantity of ammonia evolved it appeared that the primary product was a carbamate. This carbamic acid ester of ethylene glycol subsequently lost carbon dioxide with formation of the desired C—N bond as indicated by the following equations ... 

A solution of 34 cc (0.5 mol) of liquid phosgene in 150 cc of absolute ether is reacted while cooling with a mixture of sodium chloride and ice, first with 62 grams (0.5 mol) of 1-ethinyl cyclohexanol-1 and then with 64 cc (0.5 mol) of quinoline. The precipitated quinoline chlorohydrate is filtered off and the filtrate is reacted with ammonia in ether. In this manner 45 grams of the carbamic acid ester of 1-ethinyl cyclohexanol are obtained. Yield 53% of the theoretical yield. The ester boils at 108° to 110°C/3 mm and on recrystallization from cyclohexane, yields colorless needles melting at 94° to 96°C. 

Tremaine LM, Stroll JG, Ronfeld RA. Characterization of a carbamic acid ester glucuronide of the secondary amine sertraline. Drug Metab Dispos 1989 17 58-63. 

To complete this series of heterocumulene syntheses from carbonic acid derivatives, we here present the acid- and base-catalyzed alcohol elimination from carbamic acid esters (C, Figure 8.10) and the condensation of aniline and carbon disulfide to phenylisothiocyanate (F,... 

At a slightly elevated temperature, alcohols add to the C=N double bond of isocyanates according to the same mechanism. The addition products are called carbamic acid esters or urethanes ... 

Conversion of the corresponding isocyanates, resulting from the heating of the azides in benzene, with alcohols of general formula R OH, yielded the carbamic acid esters LXXVIb (150), and with amines R"R" NH, the urea derivatives LXXVIc and LXXVIIc (151, 152). 

It is well known that organophosphates, carbamates and sulfonates are acid-transfer-inhibitors of serine hydrolases because they transfer the acid moiety of the inhibitor to the serine hydroxyl of the enzyme active site (34). Extensive evidence indicates that the reaction of these inhibitors with acetylcholinesterases (AChE) appears to involve the same reaction pathway as that for the esters of carboxylic acids, i.e. acetylcholine (see (35) for review), and in fact these inhibitors are considered to be poor substrates of AChE (36), especially the carbamic acid esters ("Equation 30 ). 

Boron trifluoride and inorganic fluorides Butyllithium Calcium carbide Carbamic acid esters Chloromethylsilanes and silicon tetrachloride (V-Chlorosuccinimide Chlorosulfonic acid Cr(Vl)... 

SYNS ERSERINE ESERINE ESEROLEIN, METHYLCARBAMATE (ESTER) METHYL-CARBAMIC ACID, ESTER with ESEROLINE PHYSOSTOL... 

SYN CARBAMIC ACID, ESTER WITH SALICYLALDEHYDE DIMETHYL ACETAL... 

Thio-carbamic acid ester Alkyl thio-urea... 

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