Secondary Amine Sites Research Articles

N-functionalization of poly(ethylene glycol)-linked mono- and bis-dioxocyclams as potential ligands for Gd3+.

A number of highly functionalized dioxocyclams with acetic acid side chains on the secondary amine sites and ethylene glycol side chains on 6 and 13-positions (12a, 12b) or a tetra(ethylene glycol) side chain linking the 6 and 13 positions (15) were synthesized and characterized, as was a bis-dioxocyclam bridged across the 6 and 13 positions by tetra(ethylene glycol) groups (16). These were screened for their ability to complex Gd3+. Only ligands 15 and 16, having tetra(ethylene glycol) groups, formed such complexes.

Synthesis and characterization of polymethacrylate-based nitric oxide donors.

A synthetic path for the preparation of methacrylic homo- and copolymers containing secondary amine groups that can be converted into nitric oxide (NO) releasing N-diazeniumdiolates is described. The polymers are obtained by a multistep procedure involving synthesis of methacrylate monomers containing boc-protected secondary amine sites, free radical benzoyl peroxide initiated polymerization, deprotection of the amine sites, and subsequent reaction of the polymers with NO in the presence of sodium methoxide. Monomers with both linear and cyclic pendant secondary amines are examined as polymer building blocks. In most cases, polymers are obtained for both types with compositions that agree well with initial monomer ratios and with number average molecular weights (M(n)) ranging from 1.69 to 2.58 x 10(6) Da. The final N-diazeniumdiolated methacrylic amine polymers are shown to release NO for extended periods of time with "apparent" t(1/2) values ranging from 30 to 60 min when suspended in phosphate buffer, pH 7.4. Total NO loading and release for these materials can reach 1.99 micromol per mg of polymer and is proportional to the amine content of the polymer. It is further shown that by using a dimethacrylate cross-linking agent in conjunction with the various methacrylate amines, suspension polymerization methods can be employed to create small (100-200 microm) polymeric methacrylate microbeads. Such microbeads that can be sequentially deprotected and converted to NO release particles via in-situ diazeniumdiolate formation as carried out for the non-crosslinked polymers.

Cross-linked poly(N-acetylethylenimine) as an isoelectric focusing matrix.

Agarose and polyacrylamide are the gels used for most analytical and micropreparative electrophoresis of biopolymers. In an alternative approach that offers different physico-chemical properties from these standard gels, nonionic hydrogels and amphigels composed of poly(N-acetylethylenimine) (PAEI) and a variety of cross-linkers were prepared and used as anticonvective matrices for isoelectric focusing. PAEI was prepared from the ring opening, ionic polymerization of 2-methyl-2-oxazoline. The N-acetyl side chains were hydrolyzed with aqueous sodium hydroxide to produce secondary amine sites which were used for the attachment of cross-linkers. Several cross-linkers were tested for their suitability for electrophoresis, and the cross-linker system based on the Diels-Alder reaction between a furan and maleimide tethered to PAEI gave a moldable gel that can be reversibly converted to a sol at 80 degrees C. This gel was used for isoelectric focusing under both denaturing and nondenaturing conditions. Several protein standards were resolved as well as was achieved with polyacrylamide.

A two-step synthesis of new macrobicyclic aza-ligands starting from “trans”dioxocyclam as diprotected macrocycle

A rapid and convenient synthesis of two small aza-cryptands containing a 1,4,8,11-tetraazacyclotetradecane backbone is reported. This strategy can be applied to the preparation of many other aza-cages by varying the nature of the cross linker. Moreover, the two remaining secondary amine sites may allow the functionalization of these ligands or their grafting on a polymer.

Preparation and NMR Spectra of Hexacoordinate Metal Complexes of Mono(N-ethylethanediamine) and Mono(N-benzylethanediamine) and Crystal Structure of [Co(NH3)4(N-benzylethanediamine)] (NO3)3·1.5H2O

Abstract Mono N-ethylethanediamine and N-benzylethanediamine complexes of Co(III), Fe(II), and Fe(III) with four cyano or ammine groups were prepared. Their 1H NMR spectra were measured to determine the conformation of N-ethyl and N-benzyl groups. These N-alkyl groups take pseudo-equatorial orientation at the coordinated secondary amine. The most preferred conformation is that the methyl and phenyl groups are anti with respect to the central metal ions. The crystal structure parameters of [Co(NH3)4(N-benzylethanediamine)](NO3)3·1.5H2O were determined: P21, Z = 2, a = 8.639(3), b = 21.240(3), c = 10.897(2) Å, β = 94.11(1)°. The crystallographically independent Co complex cations had opposite absolute configuration around coordinated secondary amine sites and the benzyl groups are anti to the cobalt atom.

The structure of protonated diamines and polyamines

The reduced mobilities in air, at 200‡C, of six isomeric C7H18N2 protonated diamines, two triamines (caldine and spermidine), and two tetramines (thermine and spermine) were measured by ion mobility spectrometric (IMS) techniques. The results indicated that all these polyamines undergo proton-induced cyclization, with the proton forming a bridge between two amino groups. It appears as if the favored configuration of the protonated polyamines involves a six- or seven-membered ring rather than a bridge between the terminal amino groups. It is believed that in the tetramines the cyclic structure is formed between the two central, more basic, secondary amine sites.

Diastereoisomers of Platinum(II) Complexes with Chiral N-Substituted 1,2-Diamines. II. Structures of Dichloro[(S)-1-(2-amino-2-methylpropyl)amino-2-propanol]platinum(II)

Abstract Square-planar complexes with the formula [PtCl2(S-Hp-Mepn)], where S-Hp-Mepn is (S)-1-(2-amino-2-methylpropyl)amino-2-propanol, CH3CH(OH)CH2NHCH2C(CH3)2NH2, were synthesized and separated into three types of crystals: small imbricate crystals (1), needles (2), and plates (3). 1H NMR spectroscopy has revealed that 1 and 2 are diastereoisomers each other but that 3 consists of both diastereoisomers in 1 : 1 composition. X-Ray crystallography has shown that the diastereoisomer 2 has the absolute configuration of R about the nitrogen atom of secondary amine and 3 is a quasi-racemic compound of S(N) and R(N) isomers: 2; orthorhombic, space group P212121 with a = 10.447(1), b = 13.017(2), c = 8.764(2) Å, R = 0.043, Rw = 0.052: 3; monoclinic, space group C 2 with a = 21.530(1), b = 11.019(2), c = 13.491(5) Å, β = 125.73(1)°, R = 0.042, Rw = 0.054. But the conformations of R(N)-isomers in 2 and 3 were different. The analysis of the CD and 1H NMR spectra of 1 and 2 shows that 1 has the absolute configuration of S about the secondary amine site. For both isomers, the major conformers in aqueous solution are those with equatorially substituted N-hydroxypropyl group and are different from those found in crystals where the packing force participates.