The synthesis of two diastereomeric cyclo[Asp-N-Bn-Ser] diketopiperazines (2a and 2b) was investigated. Initial formation of the Boc-aspartyl-N-benzyl serine isopeptide methyl esters (4a and 4b) was observed, which derive from the selective O-acylation of unprotected (S)- or (R)-N-benzylserine. This unexpected O-acylation is preferred over the formation of the tertiary amide and the resulting ester bond is stable in solution to O,N-acyl transfer. The O,N-acyl migration is then triggered by cleavage of the Boc protecting group and treatment with base, which also promotes immediate cyclization to the diketopiperazines.
Selective O-acylation of unprotected N-benzylserine methyl ester and O,N-acyl transfer in the formation of cyclo[Asp-Ser] diketopiperazines / M. Marchini, M. Mingozzi, R. Colombo, C.M.A. Gennari, M. Durini, U. Piarulli. - In: TETRAHEDRON. - ISSN 0040-4020. - 66:49(2010 Dec 04), pp. 9528-9531.
Selective O-acylation of unprotected N-benzylserine methyl ester and O,N-acyl transfer in the formation of cyclo[Asp-Ser] diketopiperazines
M. MarchiniPrimo
;M. MingozziSecondo
;R. Colombo;C.M.A. Gennari;
2010
Abstract
The synthesis of two diastereomeric cyclo[Asp-N-Bn-Ser] diketopiperazines (2a and 2b) was investigated. Initial formation of the Boc-aspartyl-N-benzyl serine isopeptide methyl esters (4a and 4b) was observed, which derive from the selective O-acylation of unprotected (S)- or (R)-N-benzylserine. This unexpected O-acylation is preferred over the formation of the tertiary amide and the resulting ester bond is stable in solution to O,N-acyl transfer. The O,N-acyl migration is then triggered by cleavage of the Boc protecting group and treatment with base, which also promotes immediate cyclization to the diketopiperazines.Pubblicazioni consigliate
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