N-Carboxy-L-alanine anhydride

Abstract

C4NO3Hs, M= 115.09; orthorhombic, P212t21; a=7.749 (2), b=10.699 (3), c=6.063 (2) A; Z=4, Dm= 1"52 (by flotation), Dx= 1.52 g cm -3. The compound was synthesized from L-alanine and trichloromethyl chloroformate, and crystallized from isopropyl ether at -5°C. The final R value was 0.047 for 681 reflexions. The molecules are linked by weak hydrogen bonds formed between N(1)-H(1) and 0(3') in the b direction.Introduction. The N-carboxy anhydrides (NCA) of amino acids are the most useful monomers for the synthesis of polypeptides. These compounds are generally unstable to moisture and heating. A study has been made on a series of crystal structures of these compounds to explain their polymerizability in the crystalline state. A crystal with the approximate dimensions 0.2×0.4×0.6 mm was mounted on a Rigaku rotating-anode automated four-circle diffractometer, and the intensity data with 20< 55 ° were collected by the usual co-20 scans [8 ° (in 20) min -1] with Zr-filtered Mo K~ radiation. 693 independent reflexions were obtained, 681 of which were regarded as observed. Accurate cell parameters were determined by leastsquares refinements with 26 high-angle reflexions. The structure was solved with MULTAN (Germain, Main & Woolfson, 1970). The non-hydrogen atoms were located on an E map computed with 116 phased re-* Permanent address: . flexions (E> 1.2). When the R (ZllFol-IFclIlYlFol) value dropped to 0.13 by block-diagonal least-squares refinement, a difference Fourier map revealed all the H atoms. The weights were 0.5 for unobserved reflexions 1.3 5 Ha

Topochemical Polymerization of Amino Acid N-Carboxy Anhydrides in Crystalline State

“…The crystal structures of L-amino acid NCAs have been determined by the author et al [10][11][12][13][14][15][16]. The crystal data are given in Table 25.4.…”

N-Carboxy-DL-leucine anhydride

“…The crystal structures of amino acid NCAs were not studied for many years after the very early initial report by Leuchs (1906). We have reported the crystal structures of glycine NCA (Kanazawa et al, 1976a) and l-alanine NCA (Kanazawa et al, 1976b), and found that the ease of polymerization depended on the crystal structure (Kanazawa & Kawai, 1980). In addition, the crystal structures of -benzyl-l-glutamate NCA (Kanazawa et al, 1978a), l-leucine NCA (Kanazawa et al, 1978b), l-valine NCA (Kanazawa et al, 1984), dl-valine NCA (Takenaka et al, 1994), dl-phenylalanine NCA (Kanazawa et al, 1997), l-phenylalanine NCA and -benzyl-l-aspartate NCA (Kanazawa & Magoshi, 2003) have also been determined.…”

N-Carboxy-L-phenylalanine anhydride

“…The present author determined the crystal structures of glycine NCA (Kanazawa et al, 1976a) and l-alanine NCA (Kanazawa et al, 1976b) and discussed their polymerizability with reference to the crystal structure (Kanazawa & Kawai, 1980). In addition, the crystal structures of -benzyl-l-glutamate NCA (Kanazawa et al, 1978a), l-leucine NCA (Kanazawa et al, 1978b), l-valine NCA (Kanazawa & Ohashi, 1984), dl-valine NCA (Takenaka et al, 1994) and dl-phenylalanine NCA (Kanazawa et al, 1997) have been determined.…”