Publicação
Dialkyl imidazolinones from alpha,alpha-dialkyl glycines
| Resumo: | In recent years, our group has been involved in the use of the Ugi-Passerini reaction for the synthesis of several alpha,alpha-dialkylglycines. The C-terminal amide bond of the resulting Ugi adducts 1 proved to be very sensitive to TFA, cleaving readily by a mechanism involving an oxazolinium-type intermediate 2. This intermediate allows in situ functionalization of the C-terminus by reaction with several nucleophiles, affording different derivatives such as free acids, esters and amides. Our previous results suggested that a dipeptide could be obtained if an amino acid ester was used as the nucleophile. The results obtained so far indicate that although a small amount the required dipeptides 3 is formed, 5,5-dialkyl-imidazolin-4-ones 4 are the major products. These may result from competitive attack at the less hindered C-2 of the oxazolinium intermediate, followed by rearrangement. |
|---|---|
| Autores principais: | Costa, Susana P. G. |
| Outros Autores: | Maia, Hernâni L. S.; Lima, Sílvia M. M. A. Pereira |
| Assunto: | Alpha,alpha-dialkyl glycines Dialkyl imidazolinones |
| Ano: | 2003 |
| País: | Portugal |
| Tipo de documento: | outro |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade do Minho |
| Idioma: | inglês |
| Origem: | RepositóriUM - Universidade do Minho |
| Resumo: | In recent years, our group has been involved in the use of the Ugi-Passerini reaction for the synthesis of several alpha,alpha-dialkylglycines. The C-terminal amide bond of the resulting Ugi adducts 1 proved to be very sensitive to TFA, cleaving readily by a mechanism involving an oxazolinium-type intermediate 2. This intermediate allows in situ functionalization of the C-terminus by reaction with several nucleophiles, affording different derivatives such as free acids, esters and amides. Our previous results suggested that a dipeptide could be obtained if an amino acid ester was used as the nucleophile. The results obtained so far indicate that although a small amount the required dipeptides 3 is formed, 5,5-dialkyl-imidazolin-4-ones 4 are the major products. These may result from competitive attack at the less hindered C-2 of the oxazolinium intermediate, followed by rearrangement. |
|---|