A Nitroxide for Effecting Controlled Nitroxide-Mediated Radical Polymerization at Temperatures ≤90 °C.

Factors underlying design of a new nitroxide, 2,2,5-trimethyl-4-tert-butyl-3-azahexane-3-oxyl (TITNO), and its styrene alkoxyamine (Styryl-TITNO) for effecting nitroxide-mediated polymerization (NMP) at temperatures ≤90 °C are described. The rate coefficient, kd, for thermal dissociation of Styryl-TITNO was determined in the range 70-100 °C, giving Arrhenius parameters Ad = 2.9 × 1012 s-1 and Ed = 104.1 kJ mol-1. Due to the low value of Ed, values of kd and the activation-deactivation equilibrium constant for NMP of n-butyl acrylate (BA) and styrene are much lower at any given temperature than for alkoxyamines of more established nitroxides. Good control of molecular weight and dispersity, with negligible contributions from termination, is achieved at 90 °C for BA and at 70 °C for styrene, thus, eliminating the complicating contributions from styrene thermal initiation. Hence, TITNO and Styryl-TITNO offer new opportunities for controlled NMP at temperatures much lower than has previously been attainable.

Process improvement in amino acid N-carboxyanhydride synthesis by N-carbamoyl amino acid nitrosation.

Amino acid N-carboxyanhydrides (NCA), convenient monomer for polypeptide synthesis, are easily prepared in high purity as the result of N-carbamoyl amino acids (CAA) nitrosation by gaseous NOx (4:1 NO + O2 mixture, or NOCl) in toluene. Removal of polar side products is then efficiently carried out during subsequent work-up and crystallisation so that the resulting NCA obtained in good yield is suitable for controlled, primary amine-initiated polymerisation.

Dynamic co-evolution of peptides and chemical energetics, a gateway to the emergence of homochirality and the catalytic activity of peptides.

We propose a scenario for the dynamic co-evolution of peptides and energy on the primitive Earth. From a multi component system consisting of hydrogen cyanide, several carbonyl compounds, ammonia, alkyl amine, carbonic anhydride, borate and isocyanic acid, we show that the reversibility of this system leads to several intermediate nitriles, that irreversibly evolve to alpha-amino acids and N-carbamoyl amino acids via selective catalytic processes. On the primitive Earth these N-carbamoyl amino acids combined with energetic molecules (NOx) may have been the core of a molecular engine producing peptides permanently and assuring their recycling and evolution. We present this molecular engine, a production example, and its various selectivities. The perspectives for such a dynamic approach to the emergence of peptides are evoked in the conclusion.