Leuch’s anhydrid

A-Carboxy-a-amino acid anhydrides, also referred to as 4-substituted oxazolidine-2,5-diones, Leuchs s anhydrides, or N-carboxyanhydrides (NCA), are polymerized by bases and transition metal complexes. Polymerization proceeds with simultaneous decarboxylation to produce a polyamide... 

If the addition of a monomer to the growing chain takes place in more than one way, then the "abnormal addition, i.e. that which does not take place in the usual propagation step, might lead to termination. For example, Sela and Berger (48) assume that the anionic polymerization of Leuch s anhydride is terminated by the abnormal additions which yields carboxylate ions instead of imide ions ... 

It is well known that primary amines are efficient initiators for the polymerization of Leuch s anhydrides (oxazolidinediones) and that initiation proceeds by the addition of the amine to the monomer. This pathway has been utilized recently to synthesize polypeptide macromonomers bearing a terminal p-vinylbenzyl group 88). Copolymerization of these macromonomers with a vinylic or acrylic comonomer yields graft copolymers with polypeptide grafts. Alternately, the monomer adduct (IV) was copolymerized with styrene, and the primary amine functions of this polymer were used to initiate the polymerization of an oxazolidinedione whereby polypeptide grafts are formed 89). Such graft copolymers may be of interest for biomedical applications. 

Thus, phosgene has proven to be very effective in the preparation of N-carboxy anhydrides (NCA) from a-amino acids. These compounds 2,5-dioxo-1,3-oxazolidines (V), also called Leuch s anhydrides have widespread applications especially but not only In peptides synthesis [Scheme 194]. 

N-Carboxy anhydrides (NCA), Leuchs s anhydrides, l,3-oxazolidine-2,5-diones, cyclic compounds containing an activated carboxy group and an acyl-protected amino function, first discovered by Hermann Leuchs in 1906. Under carefully controlled conditions, NCAs can be mono-coupled to the nitrogen of an unprotected amino... 

Although the orthoester method has not been investigated kinetically, it probably can be considered as an activated monomer synthesis, a classification introduced by Bamford (131) and elaborated by Szwarc (132). Some implications of Szwarc s analysis may be pertinent to the orthoester polymerization. Szwarc has pointed out regarding a related polymerization of Leuch s anhydrides Increasing the concentration of initiator has a dual effect on the rate of such a polymerization. It increases the stationary concentration rrf growing species — a trivial effect expected in... 

Impure IR spectra of synunetric anhydrides (Fig. 45), particularly in the range of 1,690 and 1,800 cm", show absorption bands which might be allied to Leuch s anhydrides [146, 147] (excess phosgene) and N-acyl-aziridinones [148] (excess triethylamine). Though the latter was demonstrated to be the highly reactive racemization-free precursor of both the intramolecular asymmetric and the intermolecular symmetric anhydride, the tendency for racemization of the Leuch s compound during reaction with the gel-phase-bound amino component has to be considered. In two cases even a distinct dependence on the salt cation of the carboxylic component in the formation of the possible side products mentioned was observed. Exclusively thb sodium salts of Ddz-valine and Ddz-(tert. butyl)-... 

Anionic polymerization of Ai-carboxyanhydrides (Leuch s anhydrides—NCA) affords polypeptides it proceeds by nucleophilic addition onto the carbonyl function, followed by an elimination releasing CO2 ... 

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