Synthesis of α-functionalized glycine derivatives

Abstract

I. Synthesis of α-Functionalized Glycine Derivatives: α-Functionalized glycine derivatives were synthesized from the reaction of methyl α-methoxyhippurate and methyl α-methoxy-N-benzyloxycarbonylglycinate with various nucleophiles under the mild condition in the presence of Lewis acids. Lewis acids of choice were boron trifluoride etherate and titanium tetrachloride which were effective for the gene ration of the intermediate immonium ions, the reactive species resulting from the primary reaction of the substrate and Lewis acids. Nuceophiles employed to functionalize the protected glycine derivatives were thiols, phosphites, aromatic compounds, selenols, and β-keto esters. Phosphorylated glycine derivatives were hydrolyzed into α-phosphoryl glycine using trimethylsilyl iodide. Aromatized glycine prepared from the reaction with aromatic compounds was known to have the biological activities. Allylation was also carried out by the use of all silane and allyltin reagents to yield allylated glycine derivatives. II. Tetrachlorosilane Catalyzed Dithioacetalization: Tetrachlorosilane was found to be a mild and selective catalyst for the dithioacetalization of the carbonyl compounds. Various types of the aldehydes were dithioacetalized under the mild condition utilizing the title catalyst. Chemoselective dithioacetalization of the aldehyde in the presence of the ketone permitted to discriminate between them selectively. Perfect chemoselective dithioacetalization of the aromatic aldehyde compared with the aromatic ketones represented the usefulness of the title catalyst, tetrachlorosilane.