Carbomethoxy group

Diazomethane adds both to the double and triple bonds (the latter predominating) of the dipolarophile activated by a carbomethoxy group (68LA124) (Scheme 15). 

The finding that the benzoyl ester, tropacocaine (14), possessed local anesthetic activity showed that the carbomethoxy group was not required for activity. 

N-Benzoyl-Lalanine methyl ester is in turn about eight times more reactive than is its D enantiomer). The open-chain compounds may not bind to the enzyme in the same manner, however, as does the locked substrate. The conformation around the amido bond of the open-chain compounds, for example, can be transoid rather than cisoid (81). In addition, if equatorial 24 is considered to be the reactive conformer for both the Dand L enantiomers, and if the alanine methyl group is attracted to the hydrophobic aromatic binding subsite, then structures 34 and 38 would result. The L enantiomer of N-benzoyl-phenylalanine methyl ester 38 in this representation has approximately the same conformation as equatorial L-24. But attraction of the methyl of the D enantiomer to the location occupied by the methyl group of the L enantiomer causes the carbomethoxy group to move from the position it occupies in D-24. 

In contrast, substitution of oxygen for —NH— in open-chain compounds causes a great decrease in activity. He states that the heterocyclic ring of D-24 locks the carbomethoxy group at the active site and thus accomplishes the same amount of restriction as does binding of both the aromatic and acylamido groups of the open-chain analogs (82). 

Sulfoxides containing an a-chloro group 1191 or an a-trimethylsilyl group 1193 rearrange on silylation with TMSOTf 20/triethylamine or with LDA followed by TCS 14 to the olefins 1192 and 1194 in 86 and 75% yield and HMDSO 7 [22, 23], whereas a sulfoxide with an a-cyano or a-carbomethoxy group as in 1195 reacts... 

Allomerized chlorophylls are oxidized compounds at C-13, forming theC-13 OH-chlorophyU catabolites. Other common positions for modifications and/or oxidation have been found at C-3, C-7, and C-8. Pyroderivatives of chlorophylls and their degradation products, usually found in heated and processed vegetables, lack the carbomethoxy group (-COOCH3) at C-13 of ring E, which is replaced by hydrogen. 

The reaction of sulphides 59 bearing an ethynyl or a carbomethoxy group a to sulphur with f-butyl hypochlorite in methanol or ethanol gives high yields of the corresponding a-alkoxy sulphides (60) rather than sulphoxides (equation 29). Oxidation of benzo[b]thiophene with t-butyl hypochlorite in t-butyl alcohol at 30-40° gave the corresponding 2-chloro-l-benzothiophen-l-oxide 61 in 45% yield (equation 30). 

A hydroxysulfoxide was desulfurized with Ra-Ni in MeOH for 30 minutes.400 Treatment with hydrogen in the presence of catalytic amounts of Ra-Ni in EtOH caused the desulfurization of a 2,6-anhydro-2-thio sugar, the reduction of an N-oxide, and the removal of benzyl and carbomethoxy groups at the... 

Slee and LeGoff performed further investigations on the reaction of dimethyl acetylenedicarboxylate 4-20 with an excess of furan 4-21, as first described by Diels and Alder (Scheme 4.5) [la]. At 100 °C, 4-24 and 4-25 were not produced (as proposed), but rather 4-22 and 4-23, since at elevated temperature an equilibrium takes place and the primarily formed 4-24 and 4-25 isomerize to give a 6 1-mixture of the exo-endo and the exo-exo products 4-22 and 4-23, respectively. However, at lower temperature, in the primarily formed [4+2] cycloadduct the double bond substituted with the two carbomethoxy group acts as the dienophile to give the two products 4-24 and 4-25 in a 3 1 ratio with 96% yield within five weeks, as has been shown by Diels and Olsen [la,lc]. For a differentiation of these two types of adducts, Paquette and coworkers [7] used a domino and pincer product . The Cram group [8] described one of the first examples of a reaction of a tethered bisfuran 4-26 with dimethyl acetylenedicarboxylate 4-20a to give 4-27. 

The X-ray analysis of compound 2 (Figure 2) was used to confirm its structure and revealed that only the carbomethoxy group at C-l lies on the plane of indolizine nucleus as already evidenced for other 1,2,3-trisubstituted indolizidines <2000CHE1192>. 

Following the first observations by Heck that Pd(OAc)2 can substitute a hydrogen atom in ethylene by a carbomethoxy group [50], Stille and James have discovered that the [Pd - Cu] couple catalyzes the incorporation of a COOMe group arising from carbon monoxide and methanol [51]. Most of the reactions with an alkene end up with a diester or a methoxyester, copper being used in stoichiometric quantities. Cyclic alkenes give preferentially diesters (Scheme 7). 

Bakhmutov and Burmistrov (38) have studied a number of secondary enamines with a nitro group and a carbomethoxy group as acceptors (20). These exist in... 

The greater lability of complex 146.C (compared to 145.c), as evinced by the much shorter reaction time, is typical of those that bear a carbomethoxy or acetyl substituent at the central carbon of an i73-allylic ligand. The temperature required for complete decarbonylation of complexes of type 146 and 148 increases with the size of the R-substituent, which suggests a mechanism involving hydride transfer.111 This would also explain the observed activating effect of the centrally located carbomethoxy group in 146.C, which would clearly labilize the methyl proton shown explicitly in 146. 

As before, when the carbomethoxy group is bonded to the central carbon of the allyl portion of the vinylketene complex, the increased lability of a methyl proton allows the formation of a second product, in this case the diene complex 150. In the cases where R = PF(146.e and 148.a), decomplexation of the tricarbonyliron moiety allows the thermodynamically favored... 

Strain and steric properties of the alkenes determine the rate of insertion. The carbomethoxy complex (dppp)PdC(0)OCH3+ turned out to be less reactive than the corresponding acetyl-palladium (dppp)PdC(0)CH3+, which was ascribed to the higher nucleophilicity of the acetyl group as compared to the carbomethoxy group. 

On this basis it was reasoned that a benzyl group in a ketene acetal should greatly increase the extent of cleavage during polymerization and, therefore, should increase the efficiency of chain transfer. That in fact is what occurred when an equimolar mixture benzyl methyl ketene acetal (XIV) and styrene was heated at 120°C in the presence of di-tert-buty1 peroxide an oligomer with 80% styrene units and capped with a carbomethoxy group was obtained. 

This procedure illustrates a general method for the selective splitting of a carbomethoxy group in the presence of easily hydrolyzed esters of other alcohols, such as the easily hydrolyzed equatorial acetoxy group. The specificity of the reaction is not affected by steric hindrance, and a highly hindered methyl ester can be split in the presence of other less hindered esters of secondary alcohols. Normal alkaline saponification goes in exactly the opposite way. 

Penfluridol Penfluridol, 4-(4-chloro-3-trifluoromethylphenyl)-l-[4,4-Z M-(p-fluorophenyl) butyl]-4-piperidinol (6.6.12), is synthesized implementing a Grignard reaction between l-carbomethoxypiperidin-4-one and 4-chloro-3-trifluoromethylphenylmagnesium bromide, giving l-carbomethoxy-(4-chloro-3-trifluoromethylphenyl)-4-piperidinol (6.6.10). Upon alkaline hydrolysis of the carbomethoxy group, it turns into (4-chloro-3-trifluo-romethylphenyl)-4-piperidinol (6.6.11), the alkylation of which with l,l-( ti(4-fluo-rophenyl)butyl bromide (6.6.3) gives penfluridol (6.6.12) [67-69],... 

In 1996, Wu et al. reported the isolation of clausine E (25) from the stem bark of C. excavata (46). One year later, Ito et al. reported the isolation of the same alkaloid from the same source and named it clauszoline-I (25) (47). This alkaloid showed inhibition of rabbit platelet aggregation and caused vasocontraction. The UV, IR, and H-NMR spectra were similar to those of mukoeic acid (10) with respect to the position of substituents. The presence of a carbomethoxy group at C-3 was indicated by an IR band at 1703 cm . Moreover, two significant mass fragments at m/z 210 (M —OMe) and 182 (M —COOMe) confirmed the presence of a carbomethoxy group. On the basis of these spectral data, structure 25 was assigned to clausine E (clauszoline-I) (Scheme 2.6). 

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