N-Carboxy-L-alanine anhydride

H. Kanazawa, Y. Matsuura, N. Tanaka, M. Kakudo, T. Komoto, T. Kawai
1976 Acta Crystallographica Section B  
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
more » ... or 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
doi:10.1107/s0567740876010194 fatcat:gbzdgtj4zzfu5cgpdjd2gafw3y