Alkyl moieties

AdeninyUiydroxypropanoic acid alkyl esters [(R,5)-AHPA esters, (30)] represent a new class of broad-spectmm antiviral agents, which are, like (3)-DHPA, targeted at SAH hydrolase (62). The free acid, (R,3)-AHPA, is only weakly active as an antiviral agent. Thus the alkyl moiety merely serves as a protecting group to faciUtate uptake of AHPA by the cells. Within the cells, the AHPA alkyl esters would be hydroly2ed to release the free acid, which should then interact with SAH hydrolase. 

Ruthenium complexes have been used in the hydrocarbonylation of simple esters to produce the corresponding homologous esters (50). The hydrocarbonylation affects the alkyl moiety rather than the carboxylate group ... 

This small class of compounds is characterized by an N-alkyl moiety, and they are synthesized from isoxazolium salts by isomerization or by the dehydration of 2-alkyl-isoxazolidin-3-ols (Scheme 128) (74BSF1025). The reaction of isoxazolium salts that are unsubstituted in the 5-position with phenylmagnesium halides was reported to give 3-isoxazolines by 1,4-conjugate addition, and this reaction is also shown in Scheme 128 (74CPB70). 

Plasmalogens are ether glycerophospholipids in which the alkyl moiety is d5-a,/3-unsaturated (Figure 8.10). Common plasmalogen head groups include choline, ethanolamine, and serine. These lipids are referred to as phosphati-dal choline, phosphatidal ethanolamine, and phosphatidal serine. 

Elimination of carbon monoxide accompanied by conversion of an acyl group to the corresponding alkyl moiety has been termed decarbonylation. The process is represented by Eq. (12) with L = CO. 

Fig. 13 Molecular structure of 2 OEt-2 OPr-cyclo viewed along the phenylene planes. Both of the ester alkyl moieties are depicted by a propyl group.

Fig. 14 Crystal structure of 2 OEt-2 OPr. Two molecules making a pair (B and C) and two neighbouring molecules in the other pairs (A and D) viewed along the phenylene groups in molecules B and C. All the ester alkyl moieties are depicted by an ethyl group.

Starting from n-butane, 2-butoxides that rapidly convert to 2-butanone are found over MgCr204 [24]. However, the further oxidation of adsorbed 2-butanone only gives rise to the acetate species, while starting from n-butane, formate species are also observed. This can be explained assuming that sec-butoxides can partly isomerize to rert-butoxides before further oxidation. This implies that the C-O bond formed is partly ionic and the alkyl moiety has the... 

In addition to the H NMR resonances of [TpRR ]MgR attributable to the metal-alkyl moieties, the H NMR resonances associated with the [Tp1 ] ligands also provide a valuable spectroscopic handle for monitoring reactivity. For example, each of the complexes [TpBut]MgR exhibits a single characteristic resonance in the range 8 1.34-1.44 attributable to the t-butyl substituents of the [TpBut] ligand. 

Traditionally, electron transfer processes in solution and at surfaces have been classified into outer-sphere and inner-sphere mechanisms (1). However, the experimental basis for the quantitative distinction between these mechanisms is not completely clear, especially when electron transfer is not accompanied by either atom or ligand transfer (i.e., the bridged activated complex). We wish to describe how the advantage of using organometals and alkyl radicals as electron donors accrues from the wide structural variations in their donor abilities and steric properties which can be achieved as a result of branching the alkyl moiety at either the a- or g-carbon centers. 

The chain transfer constant for sites bearing the original alkyl moiety (virgin CTA sites), C °, where C0 = k.Jk... 

This molecular weight response clearly indicates that chain-shuttled ethylene-octene block copolymers, rather than blends, are formed upon introduction of DEZ. The Mn can also be used in conjunction with the DEZ feed and polymerization rate to calculate the number of chains produced per Zn molecule. The low DEZ level of sample 4 results in the production of ca. 12 chains/Zn. However, the reaction is practically stoichiometric at higher DEZ (no H2), with production of sample 6 resulting in 1.9 chains/Zn (or ca. one chain per Zn-alkyl moiety). This example indicates that nearly every polymer chain exited the reactor bound to the CSA, with very little chain termination, demonstrating the efficiency of the chain shuttling reaction. 

Fortunately, steric control arising from interactions of alkyl moieties derived from reacting olefins can be enhanced and observed by selection of appropriate reactants. This effect was demonstrated in the work of Lawrence and Ofstead (76), who studied the metathesis of 4-methyl-2-pentene induced by a WCl6Et2OBu4Sn catalyst. This catalyst is not particularly unique, for the steric course of the metathesis of m-2-pen-tene with this system was found to be essentially equivalent to that previously observed (18) with a conventional catalyst employing an or-ganoaluminum cocatalyst. 

The mixture of anionic fluorinated alkylphosphinic and -phosphonic acid surfactants with perfluorinated alkyl moieties was examined using ESI-FIA-MS-MS(—). For CID in the negative mode, precursor ions at m/z 399, 499 and 599 were selected [22]. From all precursor ions only one product ion at m/z 79 ([PO3]—) besides the [M — H] ion was... 

These observations are consistent with earlier observations, indicating that those SPC isomers with a greater resistance to further degradation stem from (Ci2-)LAS in which the phenyl ring is attached to central positions of the alkyl chain, or those which are oxidised on the shorter side of the alkyl moiety [10]. In the course of microbial degradation, subsequent shortening of the alkyl chain via (3-oxidation becomes hindered in close proximity to the aromatic ring. 

The second alkene loss can occur from any onium ion bearing at least one C2-alkyl moiety, which obviously is the least demanding prerequisite for an alkene... 

The loss of alkenes from aliphatic onium ions via onium reaction comprises scission of the C-X bond and concomitant transfer of a hydrogen from the leaving alkyl moiety to the heteroatom, and a merely phenomenological description of this reaction has already been included in the preceding schemes. 

The X-ray structure of the Cut complex 21 of phosphoramidite 14 provides additional insight into a possible mechanism for stereocontrol (Fig. 7.3). The formation of the L2CuEt-enone complex involves substitution of the iodide in 21 for the alkyl moiety and of one of the ligands for the -coordinated enone. Coordination of RZnX results in the bimetallic intermediate 19 (Fig. 7.3). The absolute configuration of the two phosphoramidite ligands and the pseudo-C2-symmetric arrangement dictate the formation of (S)-3-ethyl-cyclohexanone. 

Another, more direct approach to overcome the problem of surface reconstruction, is the variation of the mesogenic unit of the surface active molecule. Instead of using flexible n-alkyl moieties with high conformational freedom, SAMs formed from molecules featuring a rigid mesogen in which conformational disorder has been eliminated as completely as possible should be suitable for the preparation... 

The alkylation is rationalized as involving the radical addition of RaTc to the acetylene and the decomposition of the formed adduct to afford the dialkyltelluride and the olefin, originated from the displaced alkyl moiety via transfer of a hydrogen to vinyl cation. 

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