Thiazoline ring

Thiochrome (377), the well-known derivative of the 2-imino-4-thiazoline ring, is synthesized according to the set of reactions shown in Scheme 216 (704, 732). 

A new method for the construction of thiazoline rings has been reported. N-acylcysteamine derivatives 33 have been cyclised using phosphorus pentachloride under mild conditions to give a range of 2-alkyl and 2-aryl thiazolines 34. This method is particularly useful for the construction of sterically hindered thiazoline analogs, and has been used to construct micacocidin 35, a unique anti mycoplasma antibiotic <99T10271>. 

Two additional types of methyltransferase domains have been identified in NRPSs. Yersiniabactin synthetase contains a carbon-MT domain within a Cy-MT-PCP-TE module. This domain methylates at the a-carbon of an intermediate thiazoline ring. The melithiazol synthetase utilizes an MT domain in trans to form a methyl ester at the C-terminus of the natural product. Recent in silica analysis of MT domains from secondary metabolite biosynthetic pathways has revealed the boundaries of these domains and suggests that they are typically approximately 200 amino acids in length, much shorter than previously thought. The results of this study by Mohanty and coworkers allow for the accurate prediction of N-, C-, or 0-MT activity through sequence analysis. " ... 

This group comprises condensation products of salicylic acid with cysteine giving a thiazoline ring. For a review, see (570). Some structurally related compounds will also be mentioned here. Salicylic acid isolated from Burkholderia Pseudomonas) cepacia was named azurochelin (555). It was found to act as a siderophore, e.g. for Pseudomonas fluorescens (230) and P. syringae (178) see also Mycobacterium smegmatis (Sect. 2.8). For details on the siderophore activity of salicylic acid, see (559). 

An analogous set of studies demonstrated that acinetobactin from Acinetohacter baumannii (392) has actually the structure 77 shown in Fig. 27 and that the one originally proposed (Fig. 24, 78) is that of pre-acinetobactin. In contrast, the thiazoline ring of anguibactin (Fig. 24, 70) (see above Sect. 5) is stable. Acinetobactin forms a 1 1 complex with Fe ". ... 

Sansinenea E, Ortiz A (2009) Bacterial Siderophores Containing a Thiazoline Ring. Mini-Rev Org Chem 6 120... 

That the Indo-Pacific (Fig. 7.1.II) is an area of high natural product diversity was first revealed by the studies carried out in the 1970 s at the Roche Research Institute on the Great Barrier Reef (Baker 1980). Studies worldwide have since confirmed this richness, unsurpassed by any other area, either in the sea or on land. The variety of small peptides from the Indo-Pacific is impressive, characterized, particularly with the ascidians, by the condensation of the cysteine NH2 and SH groups with the COOH group of an adjacent amino acid. Thiazole and thiazoline rings are formed, which alternate with the normal peptide bonds formed by the other amino acids (Chart 7.2.P1-3). Correspondingly, threonine forms methyloxazoline moieties (Chart 7.2. A, 7.2.P1,7.2.P2). These condensations inqiose a drastic conformational bias to peptides (Abbenante 1996). 

A frequently used method for the construction of the 2-amino-2-thiazoline ring (60) involves the reaction between thiourea and 2-bromoethylamine hydrobromide.122-124 If the amine nitrogen atom is... 

Figure 5-82. The ring opening of both thiazoline rings in 5.37 leads to the formation of a penta-dentate N2S2 ligand.

The resulting thioamide 64 is subjected to cyclodehydratization with the PEG supported Burgess reagent 6225 with the sulfur atom instead of the carbonyl group performing the intramolecular attack on the sulfonate group in a similar way to that described above. The conversion of the oxazoline into a thiazoline ring as the final step yields curacin A (1). 

This chapter deals with penam and penem chemistry, that is, azetidin-2-one fused with thiazolidine and thiazoline rings, respectively, and covers the literature from 1995 till 2006. Since CHEC-II(1996) <1996CHEC-II(1B)623>, more than 29000 papers containing the keywords penicillin, penam, or penem in their title or abstract have been published. Important topics already discussed in CHEC-II(1996) have been recalled and updated with fresh references, as well as a selection of relevant studies from the recent literature has been incorporated in this chapter. 

---