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.
테트라클로로실란은 알데히드와 케톤의 티올과의 디티오아세탈화 반응에서 좋은 축합 촉매로 판명되었다. 알데히드는 위 촉매를 이용하여 온화한 조건에서 쉽게 디티오아세탈화 반응을 하였으며 높은 수율로 반응을 진행시킬수 있었다. 주목할만한 점은 테트라클로로실란은 알데히드와 케톤을 선택적으로 구분하여 디티오아세탈화 반응을 시킬 수 있다는 것이다. 즉 방향족 알데히드는 방향족 케톤하존재하에서 방향족 케톤은 전혀 축합시키지않고 거의 정량적으로 디티오아세탈화시켰다. 반면, 알리파틱 알데히드와 케톤에서는 좋은 선택성을 가지며 디티오아세탈화시켰다. 이같은 선택성은 실리콘의 산소에 대한 친화력과 카르보닐화합물의 입체 배향으로 설명할 수 있다.