Alkoxycarbonyl Derivatives

The two major adducts obtained in the reaction of 9a with cyclopentadiene were used by Koizumi et al. in the synthesis of bicyclic sesquiterpenes [31]. From 

Two main problems were associated with the use of optically pure 3-p-tolyl-sulfinyl acrylates as dienophiles. The first was due to the high number of reaction steps and consequently low overall yields involved in their preparation, and the second to the fact that these dienophiles were insufficiently reactive with a 

The stereochemical results of all these reactions were explained by assuming as predominant the conformation having the sulfinyl oxygen in an s-trans arrangement [42] but the reasons justifying the significant differences in n-fa-cial selectivity for substrates 14,25, and 26 were not discussed. 

The only report of 2-sulfinyl butenolides appeared in 1993 [50]. The synthesis of 5-ethoxy-3-p-tolylsulfinyl-2(5H)-furanones (42a and 42b) and their behavior as dienophiles in asymmetric Diels-Alder reactions with cyclopentadiene were studied. This paper evaluates the relative ability of the two chiral centers at the dienophile (sulfur and C-5) to control the stereochemical course of the reaction. From the results obtained it was concluded that both chiral centers have a 

Conditions Total vield exo/endo exo(t)/exo(c) endo(t)/endo(c) 

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The protecting group Y of the amine is generally an alkoxycarbonyl derivative since their nucleophilicity is low. Benzyloxy- or tert-butoxycarbonyl derivatives usually do not undergo azlactone formation. 

The 3-nitroindoles show interesting reactivity toward the anion of ethyl isocyanoacetate iV-sulfonyl derivatives give the pyrrolo[3,3-b indole ring system lEq. 10.38. " On the other hand, iV-alkoxycarbonyl derivatives give the normal product, the pyrrolo[3,4-li indole ring system fEq, 10,39, ... 

Buur, A., Bundgaard, H., Prodrugs of 5-fluorouradl V. 1-alkoxycarbonyl derivatives as potential prodrug forms for improved rectal and oral delivery of 5-fluorouradl, ]. Pharm. Sci. 1986, 75, 522-527. 

Carbonic acid esters (alkoxycarbonyl derivatives) are diesters of general formula R-O-CO-O-R. A single mechanism operates in the HO -catalyzed (and presumably also in the enzyme-catalyzed) hydrolysis of carbonic acid esters, namely a rate-determining addition of the base to the carbonyl C-atom to form an intermediate whose breakdown yields the drug (ROH), C02, and an alcohol (R OH) (Fig. 8.7,a) [153],... 

As is to be expected, an alkynic ketone undergoes a Michael addition with a carbanion, leading eventually to a pyranone (50JA1022). Using malonic esters, a 3-alkoxycarbonyl derivative results, which is hydrolyzed to the 2-oxopyran-3-carboxylic acid under alkaline conditions, but to the pyranone by sulfuric acid. Rapid ester exchange is observed with the initial products, the alcohol used as solvent determining the nature of the alkyl group in the 3-carboxylic esters (Scheme 90). 

Several strategies enable the attachment of guanidines and amidines to insoluble supports (Figure 3.29, Table 3.28). These include attachment as A-benzyl, A-acyl, and A-alkoxycarbonyl derivatives. Furthermore, support-bound isothioureas can be used to convert amines into guanidines. The synthesis of support-bound guandines is considered in Section 14.3. 

Especially the a-methoxylation or acetoxylation of amides like A-acyl and N-alkoxycarbonyl derivatives of amines, amino acids, and peptides leads to the synthetically very useful N,0-acetals, which are powerful amidoalkylation reagents [26] ... 

The key palladium intermediate is a carboalkoxypalladium complex formed through the nucleophilic attack by alcohol on carbonyl coordinated to palladium. The addition of a base with the appropriate pK, [sodium butyrate pK, = 4.82 (H20)] promotes the formation of die palladium carboxylate (22).93 The reaction is a general method for formation of inorganic alkoxycarbonyl derivatives. 

Buur, A. andH. Bundgaard. 1984b. Prodrugs of Serouracil. II. Hydrolysis kinetics, bioactivation, solubility and lipophilicity of N-alkoxycarbonyl derivatives of 5- uorouraoftrch. Pharm. Chem., Sci. Ed. 12 37-44. 

Several iV-alkoxycarbonyl derivatives of 2-amino-2-deoxy-D-glucose have been prepared in this way by reacting D-fructose with the appropriate amino acid.84 The rearrangement is catalyzed by ammonium chloride, and the epimer with the d-gluco configuration is formed preferentially. Such derivatives, when formed from optically active amino acids, are diastereo-isomers, separable by chromatography this observation has been used for the resolution of DL-alanine, since the rearrangement can be reversed, and the amino acid can be recovered by alkaline treatment. 

Synthesis and Polymerization of Leuchs Anhydrides. The N-carboxy-a-amino acid anhydrides, referred to as Leuchs anhydrides or as NCAs, are synthesized either from N-alkoxycarbonyl derivatives of a-amino acids or from free amino acids. Cyclization of the amino acid derivative by SOCl2 or similar reagents was described first by Leuchs in 1906, but direct synthesis involves treating the a-amino acid or its hydrochloride with phosgene as shown in Figure 4. This method, commonly termed the Fuchs-Farthing method, is the one that is used most frequently since the N-carboxyanhydride may be freed easily from the carbamyl chloride, isocyanate derivative, and hydrogen chloride by crystallization. 

When X = OAc , the initially coordinated anion is sufficiently basic to neutralize the liberated H+ [Eq. (54)] however, X = Cl requires the presence of external (normally amine) base to effect the same transformation. In both cases the palladium is recovered as the carbonyl derivative, Pd(CO)(PPh3)3 [and/or the related Pd3(CO)3(PPh3)4]. Alkoxycarbonyl derivatives such as Pd(OAc)(COOMe)(PPh3)2 and Pd(COOMe)2(PPh3)2 have been isolated from these systems and are invoked as catalytic intermediates, the total mechanism being described in the Scheme 10. The salient... 

On the contrary, this latter species is easily dccarbonylated to the corresponding alkoxycarbonyl derivative. 

Ligand (94) or its C-methyl derivative [tris(pyrazol-l-yl)ethane] (represented by L) affords iridium complexes which react with carbon monoxide and methanol to yield alkoxycarbonyl derivatives [(L)IrH(C02Me)(C0)] (Equation (1)) <89JOM(366)245>. This constitutes an interesting example of alcohol activation. 

In a similar manner, nitrones 32c,133 32d,129 and 32e112 with various monosubstituted olefins afford the corresponding isoxazolizidines (33c-e). 4-Hydroxy-3-nitroisoxazoline-A(-oxide (321) is thoroughly investigated. With olefins 3, such as propylene, styrene, vinyl acetate, methyl acrylate and acrylonitrile, adducts 33f are formed.134 Reactions of alkoxy or alkoxycarbonyl derivatives of 32 are also known these include 32g,133 3 2h,13 32i,135 and 3 j135 32j is reactive enough to cyclize... 

Addition to chiral pyridinium salts. A/-Alkyl-" or A-alkoxycarbonyl derivatives are equally susceptible to asymmetric induction during attack at C-2. 

The facile decarboxylation of resorcinol carboxylic acids and notably of orsellinic acids in alkaline solution poses a problem during their syntheses in high yield. For this reason the synthesis of alkoxycarbonyl derivatives is usually adopted followed by acidic hydrolysis. The removal of the protective acetyl groups in the compound shown was effected preferentially without hydrolysis of the ester group. Methyl 2,6-diacetoxybenzoate in toluene saturated with water when add to a catalyst (prepared from 4-toluenesulphonic acid monohydrate and silica gel) and stirr at 86°C during 6 hours, afford methyl... 

Their n.m.r. spectra indicate trans geometry with a high barrier to rotation about the C—bond. Analogous thiocarboxamido-compounds [MCIL2-(CSNMe2)] were obtained by oxidative addition of ClC(S)NMe2 to [MLJ. Both series of complexes are air-stable solids which are stable in water, in contrast to similar alkoxycarbonyl derivatives. 

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