Synthesis Of Substituted Thiazoles And Oxazoles From Natural ?-amino Acids

Amino acids are biosynthetic building blocks for the construction of alkaloids and polypeptides.It has the advantages of being non-toxic,inexpensive,and easy to obtain,meeting the requirements of modern organic synthesis and green chemistry.In recent years,the application of amino acids in organic transformation has been extensively studied,especially for synthetic methodology.Up until now,people have developed many ways to use their reactivity to build organic molecular scaffolds.In this dissertation,natural ?-amino acids are used as the substrate,amino acids undergo degradation to form aldehydes in the I2-DMSO system.Then they are captured by different molecular fragments achieve 2,5-disubstituted thiazole and oxazole substitutions and the related reaction mechanisms were discussed.It mainly includes the following parts:In the first chapter,the research progress of amino acid and its derivatives in organic synthesis is summarized,and then we summarized the literature of the synthesis methods to thiazole and oxazole in modern synthesis methodology.In the second chapter,based on the analysis of amino acid polymerization from the backbone fragments of thiazole and oxazole in many polypeptides,we describe the development of a dimerization procedure for amino acids to prepare 2,5-disubstituted thiazoles and oxazoles in the presence of an additional S/O source.Mechanically,decarboxylation,deamination,S/O insertion,cyclization and gradient oxidation processes were involved in the oligomer formation.In the third chapter,based on so many literatures related to phenylacetylene,we found that the triple bond of terminal alkyne is easily activated by metal catalyst to undergo cyclization reaction.Therefore,we added it into the I2/DMSO reaction system with aliphatic and aromatic amino acid and found that they could produce 2,5-disubstituted oxazoles.