Carbamate linkage units

It should be added that the emergence of PNA has resulted in a resurgence of research on the introduction of amide (or carbamate) linkages between the ribose units of nucleic acids first described by Halford and Jones in 1968 [43]. One such structure called HNA, hexose nucleic acid, demonstrates the ability to hybridize to nucleic acids [44]. These types of oligonucleotide mimics have been reviewed [45]. 

Cholesterol as well as unsaturated or saturated hydrocarbon chains are used as lipophilic lipid anchors. Although Cl 8-hydrocarbon chains (oleoyl or oleyl unit) are only used in unsaturated compounds, structural variations with C14-, C16-, or even Cl 8-hydrocarbon chains in saturated compounds are known (27). The lipophilic units are linked with a parent structure (usually glycerol) via ether (e.g., DOTMA) or ester bridges (e.g., DOTAP). Ester bridges are often used to create the linkage to avoid cytotoxicity, because ether bonds are more difficult to break down biologically than ester bonds (58). Substances that are easy to decompose and are therefore often used as a spacer are carbamate units (29) [e.g., 3p-[A-(A, A -dimethylaminoethyl)carbamoyl]-cholesterol (DC-Chol)], amide units, or phosphate esters. However, a direct correlation between toxicity and the... 

A polymer in which the monomer units are bonded together by carbamate ester (urethane) linkages, (p. 1034)... 

The conformationally-locked 3 -amino thymidine derivative (47) was prepared and incorporated into DNA as a dimer unit, attaching the amino group via a carbamate or phosphoramidate linkage.Both modifications were found to be destabilising towards both RNA and DNA targets. The hybridisation properties of an amino-modified bicyclic thymine nucleotide (48) have been exam-ined. Using alternate T and (48) residues there is an increase in duplex stability with d(A)io, with no pH dependence. When the amino group is acetylated, the duplex stability is decreased. The locked C-nucleoside oxazole derivative (49) has been incorporated into TFOs where it was found to selectively enhance the stability with a C.G base pair. ... 

Polyurethane (PU) is a polymer composed of a chain of organic units joined by carbamate (urethane) links. PU polymers are formed by combining two bi-fimctional (or higher) monomers, one of which contains two or more isocyanate functional groups with the formula — N=C=0, while the other contains two or more hydroxyl groups. The isocyanate and hydroxyl groups combine to form a urethane linkage ... 

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