Thiazole molecular structure

The crystal and molecular structures of 2-amino-4-phenylthiazole hydrobromide have been determined by radiocrystallography the angle between the thiazole and phenyl rings was found to be 19 . The major features are reported in Fig. VI-4 (142). 

We reported in the previous papers [8, 9] that the effect of the operational factors such as temperature and solvents on the polymorphic crystallization of a thiazole derivative - 2-(3 -Cyano-4-(2-methylpropoxy)-phenyl)-4-methyl-thiazole-5-car-boxylic acid (BPT) - which is an enzyme inhibitor. In this paper, we synthesized the esters of BPT and studied the effect of the molecular structure on polymorphic nucleation systemically, and at the same time we also examined the solvent effect on the polymorphic nucleation of the ester. 

Figure 4 Molecular structure of thiazole bond lengths (A) and bond angles (°)...

Microwave spectroscopy is a powerful tool for the determination of molecular structure. Thiazoles and thiadiazoles have been studied by this technique, but it was not until 1976 that a paper on the microwave spectrum of 1,2,3-thiadiazole appeared. Bond distances and angles for 1,2,3-thiadiazole (7) are listed in Table 4 (76MI42400). The success of this project is owed in part to the development of double resonance modulated (DRM) microwave spectroscopy which allows for quick analysis of an individual spectrum. 

Rg.I-6. Molecular structure of thiazole bond lengths in A (left), bond angles in degrees (right). 

Fig. 1-6). The structure obtained for thiazole is surprisingly close to an average of the structures of thiophene (169) and 1,3,4-thiadiazole (170) (Fig. 1-7). From a comparison of the molecular structures of thiazole, thiophene, thiadiazole. and pyridine (171), it appears that around C(4) the bond angles of thiazole C(4)-H with both adjacent C(4)-N and C(4)-C(5) bonds show a difference of 5.4° that, compared to a difference in C(2)-H of pyridine of 4.2°, is interpreted by L. Nygaard (159) as resulting from an attraction of H(4) by the electron lone pair of nitrogen. 

The molecular structure of thiazole has been refined by the joint analysis of data obtained from gas-phase electron diffraction (GED), microwave (MW) spectroscopy, and ab initio molecular orbital (MO) calculations. The combined approach, making use of the structure analysis restrained by ab initio calculations for electron diffraction (SARACEN) method, has led to a very precise structure in which all independent geometric parameters are well defined <1999PCP2421>. The refined bond lengths and angles are listed in Table 1, and these agreed well with experimental data previously obtained (see Section 4.06.3.2 and Section 3.06.02 of CHEC-II(1996)). 

Figure 7.13. Molecular structures of N-Fmoc-protected oxazole (14) and thiazole (15) amino acids used as monomers of oligomer libraries.

Vitamin (thiamine, aneurine) has the molecular structure of a pyrimidine and a thiazole ring bridged by a methylene group the molecular weight is 337.3 dal-tons. It contains a quarternary nitrogen atom. The water-soluble, white, crystalline solid is stable in acidic solution but less stable in neutral or alkaline solution. Thiamine is present in high concentrations in yeast, in the pericarp, and germ of cereals. Whole rice and wheat flour are the main sources for this vitamin, but it is present in practically all plant and animal tissues. 

An extract from the soluble stromal proteins of purified and intact spinach-leaf chloroplasts was prepared by lysis of the cells in buffer, centrifugation of the suspension of broken cells, and concentration of the supernatant with removal of insoluble material. This extract contained all of the enzymes involved in the condensation of the cyclic moieties of thiamine, thiazole, and pyramine. Thus, the synthesis of thiamine in this extract following the addition of pyramine and putative precursors was a proof that the system had the possibility of building the thiazole. It was found that L-tyrosine was the donor of the C-2 carbon atom of thiazole, as in E. coli. Also, as in E. coli cells, addition of 1 -deoxy-D-f/irco-pen-tulose permitted synthesis of the thiamine structure. The relevant enzymes were localized by gel filtration in a fraction covering the 50- to 350-kDa molecular-mass range. This fraction was able to catalyze the formation of the thiazole moiety of thiamine from 0.1 -mM 1-deoxy-D-t/ireo-pentulose at the rate of 220 pmol per mg of protein per hour, in the presence of ATP and Mg2+. 

The work of Taddei et al.230 on imidazol2,1 -6]thiazole 337 and derivatives has interesting implications on the structure of azapen-talenes, and an important aspect of this study is that the molecular geometry used for calculations on 6-phenylimidazo[2,l-6]thiazole 417 was obtained from X-ray structure determinations130b (Section V,A). The reactivity of this system (Scheme 18, Section IV,C,4,b) is better correlated with Tr-electron densities than with total charges, and 7r-bond orders (by the PPP method) show that the thiazole part of the molecule is more localized than the imidazole part (Section VII). Proton chemical shifts, except that of the H2 proton a to sulfur (Section V,G,2), vary linearly with the total charge carried by the ring carbon atoms. 

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