Terminal moieties

Complexes of tetravalent zirconium with organic acids, such as citric, tartaric, malic, and lactic acids, and a complex of aluminum and citric acid have been claimed to be active as dispersants. The dispersant is especially useful in dispersing bentonite suspensions [288]. Polymers with amine sulfide terminal moieties are synthesized by using aminethiols as chain transfer agents in aqueous addition polymerizations. The polymers are useful as mineral dispersants [1182]. 

Polymers with Amine Sulfide Terminal Moieties... 

Systematic variation in chirality at both the chelate backbone and the terminal groups revealed a remarkable effect on the enantioselectivity of the catalysts. Ligand (109) generates chiral cooperativity between the backbone and the terminal moieties in Pt-catalyzed hydroformylation. The highest ee (65%) for 2-phenylpropanal was found for the ligand R-bis(S)-(110) in combination with Pt. The chemoselectivities with all ligands described in association with Pt were rather low. The comparative... 

Proanthocyanidins of the B-type are characterized by singly linked flavanyl units, usually between C-4 of the chain-extension unit and C-6 or C-8 of the chain-terminating moiety. They are classified according to the hydroxylation pattern of the chain-extension units (see T able 11.1). 

Notable from Table 11.10 and Table 11.11 is the considerable number of proteracacini-dins and promelacacinidins at both the di- and trimeric levels possessing 2,3-cis-3,A-cis-flavan-3,4-diol terminating moieties. It has been demonstrated that melacacidin (158) is basically inert toward solvolysis or epimerization at This was recently confirmed... 

Desired chemical functionality may also be introduced into SA monolayers via in situ cleavage of unsaturated surfactants. Crown-ether-complexed potassium permanganate was shown to break the carbon-carbon double bonds in the substrate-immobilized, unsaturated surfactants and to convert them to carboxyl groups. Slow lateral propagation of this bond breaking resulted in the formation of shorter monolayers with exposed terminal moieties (Fig. 22) [195]. 

In recent years, a variety of polymers containing azo functions have been described. The azo group can either be sited as part of the backbone chain or as part of side groups along the main chain. Polymers in which the azo group is part of the terminal moiety can be considered as a special case of those polymers having azo groups as part of their backbone chain. 

Where the azo groups form part of the polymer backbone their decomposition leads to a simultaneous fragmentation of the polymer. In the presence of a suitable monomer the radical terminated polymer fragments can initiate a polymerization and become part of a block copolymer. Thermolysis of azo functions which form part of the terminal moiety of a polymer also lead to block copolymers, but in this case no fragmentation of the azo-containing polymer occurs. 

Metallocenes have frequently been used as terminal moieties in dendrimer chemistry - as already demonstrated in previous sections. They are of interest primarily because of their potential application in catalysis [123]. An unusual metallodendrimer with peripheral ferrocene entities and optically active ferro-cenyldiphosphine ligands (josiphos ligands) was prepared by Togni et al. (Fig. 4.58) [124]. Adamantanetetracarboxlic acid was one of the core units employed. 

The three orthogonally removable lysine protecting groups we use here are Fmoc (9-fluorenyl methoxy carbonyl), cleavable with 20% base, preferably with 20% piperidine or 3% DBU (l,8-diazabicyclo[5.4.0]undec-7-ene) (18), Dde (1-(4,4-dimethyl-2,6-dioxocyclohexylidene)-ethyl), cleavable with 2% hydrazine, and Aloe (allyloxy carbonyl), cleavable with palladium. Hydrazine also removes Fmoc, and thus it can be applied only if no Fmoc groups are present on the growing peptide chain. Acid-sensitive amino protecting groups available are Boc (tert-butyloxy carbonyl), cleavable with 90% TFA, and Mtt (4-methyl-trityl), cleavable with 1% TFA. We use Boc for the protection of the N-terminal moieties of N-terminal amino acids in each peptide chain as well as at the N-terminus of the scaffold. 

The last type of these fragments results from the complete loss of the side chain and is symbolized as v . This fragment containing the C-terminal moiety is intense for amino acids that do not easily yield w type fragments. No equivalent containing the N-terminal moiety has ever been observed. 

In these complexes, the two Ru(bpy)2 terminal moieties are bridged by a 2,2 -bis(benzimidazol-2-yl)-4,4 -bipyridine ligand, the metal-metal distance reaching 11 A [69]. An intervalence band has been observed at 1200 nm, from which a 120 cm coupling (0.015 eV) is determined. Although this value is low in comparison with other complexes, the system is extremely appealing, since the intervalence band, and thus the coupling, can be switched OFF upon deprotonation. 

Lesopitron (110), a buspirone analog with a chloropyrazole as the terminal moiety, has moderate affinity for the lA receptor (101 nM), where it acts as a pre- and postsynaptic agonist (453,454).In an important distinction... 

As will be seen later, peptide-bond formation can be achieved by converting the intended TV-protected TV-terminal residue into a reactive derivative of the carboxy function in the absence of the C-terminal moiety to which it is to be coupled. In these circumstances, it is not always necessary to protect the carboxy group of the latter. The C-terminal moiety then has both the a-amino group and the terminal... 

In general, the placement of reactive functionalities on the exterior surface of the dendrimers allows introduction of a wide variety of terminal moieties. In alternate synthetic approaches, spacer groups have been deliberately introduced to relieve the steric hindrance in order to faciUtate construction of the next generation. This may provide the possibility of enhancing interior cargo spaces for guest-host type chemistry. ... 

Remove the DCDM-treated slide (top slide) from the MTPTS-treated slide. This will reveal a thin film of highly crosslinked sugar polyacrylate hydrogel containing a carboxyl or amine-terminated moiety covalently attached to the MTPTS-treated surface. 

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