Synthesis of the pyridine core of cyclothiazomycin

A highly convergent synthesis of the pyridine core of the thiopeptide antibiotic cyclothiazomycin has been developed based on a [2+2+2] cyclotrimerization key step. The regioselective assembly of the heterocyclic center of this important class of antibiotics takes advantage of a temporary silicon tether and the ruthenium-catalyzed cyclotrimerization reaction of a diyne and an electron-poor thiazole nitrile.     

Total synthesis of the thiopeptide antibiotic amythiamicin D

The thiopeptide (or thiostrepton) antibiotics are a class of sulfur containing highly modified cyclic peptides with interesting biological properties, including reported activity against MRSA and malaria. Described herein is the total synthesis of the thiopeptide natural product amythiamicin D, which utilizes a biosynthesis-inspired hetero-Diels-Alder route to the pyridine core of the antibiotic as a key step. Preliminary studies using a range of serine-derived 1-ethoxy-2-azadienes established that hetero-Diels-Alder reaction with N-acetylenamines proceeded efficiently under microwave irradiation to give 2,3,6-trisubstituted pyridines. The thiazole building blocks of the antibiotic were obtained by either classical Hantzsch reactions or by dirhodium(II)-catalyzed chemoselective carbene N-H insertion followed by thionation, and were combined to give the bis-thiazole that forms the left-hand fragment of the antibiotic. The key Diels-Alder reaction of a tris-thiazolyl azadiene with benzyl 2-(1-acetylaminoethenyl)thiazole-4-carboxylate gave the core tetrathiazolyl pyridine, which was elaborated into the natural product by successive incorporation of glycine and bis-thiazole fragments followed by macrocyclization.     

Thiopeptide Engineering: A Multidisciplinary Effort towards Future Drugs

The recent development of thiopeptide analogues of antibiotics has allowed some of the limitations inherent to these naturally occurring substances to be overcome. Chemical synthesis, semisynthetic derivatization, and engineering of the biosynthetic pathway have independently led to complementary modifications of various thiopeptides. Some of the new substances have displayed improved profiles, not only as antibiotics, but also as antiplasmodial and anticancer drugs. The design of novel molecules based on the thiopeptide scaffold appears to be the only strategy to exploit the high potential they have shown in vitro. Herein we present the most relevant achievements in the production of thiopeptide analogues and also discuss the way the different approaches might be combined in a multidisciplinary strategy to produce more sophisticated structures.     

Asymmetric total synthesis of (-)-mycothiazole

[structure: see text] In this Letter we describe the first total synthesis of mycothiazole, a polyketide thiazole from a marine sponge. Key steps include our CMD oxidation for the conversion of thiazolidine 11 to thiazole 12 and the Nagao acetate aldol reaction of 5 with aldehyde 4 to construct the chiral secondary alcohol. The skipped diene was constructed by the standard Stille coupling, and the conjugated diene was synthesized by lithium(I)- and copper(I)-mediated Stille coupling.     

Synthesis of saramycetic acid

The first reported synthesis of saramycetic acid, a degradation product of the complex thiopeptide antibiotic cyclothiazomycin, is achieved in nine steps and 11% overall yield from diethoxyacetonitrile by a strategy, which incorporates two Hantzsch thiazole syntheses using thioamides prepared from the corresponding nitriles without the use of gaseous H₂S. The synthetic material was transformed to methyl saramycetate, which had spectroscopic properties in excellent agreement with the literature data.     

Total syntheses of amythiamicins A, B and C

Total syntheses of the thiopeptide antibiotics amythiamicins A, B and C are reported.     

Synthesis of Triarylpyridines in Thiopeptide Antibiotics by Using a C−H Arylation/Ring‐Transformation Strategy

We have described a C?H arylation/ring‐transformation strategy for the synthesis of triarylpyridines, which form the core structure of thiopeptide antibiotics. This synthetic method readily gave 2,3,6‐triarylpyridines in a regioselective manner by a two‐phase approach: C?H arylation (a nickel‐catalyzed decarbonylative Suzuki–Miyaura cross‐coupling and decarbonylative C?H coupling for the synthesis of 2,4‐diaryloxazoles) and ring transformation ([4+2] cycloaddition of 2,4‐diaryloxazoles with (hetero)arylacrylic acids). To showcase these methods, we have accomplished the formal synthesis of thiopeptide antibiotics GE2270 s and amythiamicins.     

Biosynthesis inspired Diels-Alder route to pyridines: synthesis of the 2,3-dithiazolylpyridine core of the thiopeptide antibiotics

Reaction of serine derived 1-alkoxy-2-azadienes with dehydroalanine derived dienophiles results in Diels-Alder reaction and aromatisation to give 2,3,6-trisubstituted pyridines, thereby establishing the viability of the proposed biosynthetic route to the pyridine ring of the thiopeptide antibiotics originally proposed by Bycroft and Gowland.     

硫代磷酰基硫脲与某些含氯双官能团试剂的成环反应

Ｏ－乙基－Ｎ－异丙基硫代磷酰硫脲衍生物与氯乙酰氯、二氯乙酰氯及三氯乙酰氯，在碱存在下可发生关环反应，得到相应的噻唑啉酮类衍生物，讨论了不同试剂及反应条件对产物结构的影响，而Ｏ－乙基－Ｎ－异丙基硫代磷酰硫脲与氯乙醛关环，则生成相应的噻唑衍生物，所有化合物经元素分析、＾１ＨＮＭＲ、ＩＲ及ＭＳ证实，其中部分化合物显示出一定的除草活性。     

Total synthesis of mycothiazole, a polyketide heterocycle from marine sponges

Mycothiazole isolated from marine sponges has been efficiently synthesized in a convergent manner. The key reactions involve the thiazole synthesis by dehydrogenation of the thiazolidine with chemical manganese dioxide (CMD), the Stille coupling, and the Nagao asymmetric acetate aldol reaction using the chiral 1,3-thiazolidine-2-thione. This synthesis clearly established the absolute configuration of natural mycothiazole to be (R).     

Steroidal thiazoles,isothiazoles, thiazolines and thiazolidines

In order to discover new useful steroids in which the cyclopentanoperhydrophenanthrene system is condensed with various heterocyclic rings, many new compounds are continually being synthesized and tested for physiological action. The thiazole, isothiazole, thiazoline and thiazolidine ring condensed on several positions of the steroidal skeleton, has shown great interest due to the physiological properties. Literature coverage for this review includes publications which appear from 1946 to the 1980′s.     

Synthesis,Docking, and Anticancer Activity of New Thiazole Clubbed Thiophene,Pyridine, or Chromene Scaffolds

2‐Cyanoacetamido‐4‐methylthiazole ( 1 ) was utilized as a versatile precursor for the construction of new thiazole clubbed thiazolidine, thiophene, pyridine, or chromene scaffold. The base‐catalyzed addition of 1 to phenyl isothiocyanate followed by subsequent treatment of the produced thiocarbamoyl intermediate with ethyl chloroacetate or chloroacetonitrile furnished the corresponding thiazolyl‐thiazolidine and thiazolyl‐thiophene hybrids. The reactions of compound 1 with chemical reagents, namely, acetylacetone, malononitrile, and/or 2‐(4‐anisylidene)‐malononitrile have been studied and furnished the corresponding thiazole‐pyridine hydrides 8 – 10 . Furthermore, treatment of the precursor 1 with salicylaldehyde, various aryl diazonium chlorides, and/or aromatic aldehydes afforded their corresponding thiazolyl‐chromene hybrid 12 , arylhydrazono‐nitriles 13 , and unsaturated nitriles 14 , respectively. The cytotoxicity of the synthesized compounds was screened against the cell lines HepG2, HCT‐116, and MCF‐7. Compounds 8 , 10 , and 12 recorded the best results, which was illustrated by molecular docking. Molecular Operating Environment molecular docking calculations carried out here is to rationalize correlation between docking results and biological data of thymidylate synthase (Protein Data Bank code: IHVY) inhibition. Docking has been carried out in the same co‐crystallographic inhibitor binding site to predict if the binding mode of active compounds is analogous to that of native inhibitor.     

Synthesis of methyl sulfomycinate, sulfomycinic amide and sulfomycinine, degradation products of the sulfomycin thiopeptide antibiotics

The convergent synthesis of methyl sulfomycinate and sulfomycinic amide, two acidic methanolysis products of the sulfomycin thiopeptide antibiotics, is achieved starting from diethoxyacetonitrile. Further confirmation of structure is obtained by heating methyl sulfomycinate at 110 °C in hydrochloric acid to give (±)-sulfomycinine hydrochloride, the acid hydrolysate of sulfomycin I.     

新型含2-取代-1,3-噻唑烷和噻唑环的亚胺类化合物的合成及生物活性

通过4-[(2-氰基亚胺基-1,3-噻唑烷-3-基)甲基]-2-氨基噻唑与取代苯甲醛的缩合反应, 合成了14个新型含2-取代- 1,3-噻唑烷和噻唑环的亚胺类化合物5. 所有化合物的结构均经1H NMR和元素分析确证, 并通过X射线单晶衍射分析测定了化合物5a的晶体结构. 初步生物活性试验结果表明, 部分目标化合物具有一定的杀菌活性和植物生长调节活性.     

新型含2-取代-1,3-噻唑烷环的噻唑酰胺类化合物的合成与生物活性研究

为了寻找新的含噻唑杂环的先导化合物,利用¨(2-氰基亚胺基-1,3-噻唑烷-3-基)甲基]-2-氨基噻唑与取代苯甲酰氯(或乙酰氯)在吡啶存在下发生缩合反应,合成了19个新型含2-取代-1,3-噻唑烷环的噻唑酰胺类化合物4.经1HNMR和元素分析对目标化合物的结构进行了表征,经MS进一步证实了化合物4s的结构,并通过X射线单晶衍射分析测定了化合物4a的晶体结构.对所合成的目标化合物进行了生物活性测试,部分化合物表现出一定的杀菌和植物生长调节活性.     

A new mild method for the one-pot synthesis of pyridines

Polysubstituted pyridines are prepared in good yield and with total regiocontrol by the one-pot reaction of an alkynone, 1,3-dicarbonyl compound and ammonium acetate in alcoholic solvents. This new three-component heteroannulation reaction proceeds under mild conditions in the absence of an additional acid catalyst and has been used in the synthesis of dimethyl sulfomycinamate, the acidic methanolysis degradation product of the sulfomycin family of thiopeptide antibiotics.     

Differential effects of thiopeptide and orthosomycin antibiotics on translational GTPases

The ribosome is a major target in the bacterial cell for antibiotics. Here, we dissect the effects that the thiopeptide antibiotics thiostrepton (ThS) and micrococcin (MiC) as well as the orthosomycin antibiotic evernimicin (Evn) have on translational GTPases. We demonstrate that, like ThS, MiC is a translocation inhibitor, and that the activation by MiC of the ribosome-dependent GTPase activity of EF-G is dependent on the presence of the ribosomal proteins L7/L12 as well as the G' subdomain of EF-G. In contrast, Evn does not inhibit translocation but is a potent inhibitor of back-translocation as well as IF2-dependent 70S-initiation complex formation. Collectively, these results shed insight not only into fundamental aspects of translation but also into the unappreciated specificities of these classes of translational inhibitors.     

First synthesis of an amythiamicin pyridine cluster

The pyridine-containing central domain of the amythiamicin group of thiopeptide antibiotics is prepared in protected form in 9 steps, 93%ee and 18% overall yield from (S)-2-[1-(tert-butoxycarbonylamino)-2-methylpropyl]thiazole-4-carboxylic acid by Michael addition-cyclodehydration of a 2-(2-thiazolyl)enamine and 1-(2-thiazolyl)propynone.     

An unusual labilization of a 4-(trifluoromethyl)thiazole

N-Chloro-4-(trifluoromethyl)-5-thiazolyl-N',N'-diethylurea 5 has been found to undergo a facile labilization of the trifluoromethyl group under mild conditions. The reaction relies on the assistance of the nitrogen substitution at the 4-position of the thiazole ring. Treatment of 5 with triethylamine and either methanol or methanethiol replaced the trifluoromethyl group with a methyl ester or a trimethylorthothio ester respectively at room temperature. Combination of 5 with diethylamine led to an unusual thiazolidine with two exocyclic double bonds, 8 .     

Antioxidant activity of some N-heterocycles derived from 2-(1-(2-oxo-2H-chromen-3-yl)ethylidene) hydrazinecarbothioamide

Efficient and convenient synthesis of coumarin derivatives was accomplished via reactions of 2-(1-(2-oxo-2H-chromen-3-yl)ethylidene)hydrazinecarbothioamide with some carbon electrophiles, e.g. maleic anhydride, dimethyl acetylenedicarboxylate, 1,2-dichloroethane, 3′-nitro-w-bromoacetophenone, N-(4-acetylphenyl)-2-chloroacetamide, ethyl cyanoacetate/3-chlorobenzaldehyde and acetylacetone to construct some N-heterocycles such as thiazolidine, thiazole, pyrimidine and pyrazolone derivatives. The structures of all synthesized products were substantiated from their analytical and spectral data. The antioxidant activities of the synthesized compounds were examined.