The Gas-Solid-Phase 2,5-Dioxopiperazine Synthesis. Cyclization of Vaporous Dipeptides on Silica Surface
作者:Vladimir A. Basiuk、Taras Yu. Gromovoy
DOI:10.1135/cccc19940461
日期:——
The "gas solid-phase" method is used for the preparation of both symmetric and asymmetric 2,5-dioxopiperazines via cyclization of vaporous linear dipeptides in the presence of silica.
“气固相”方法用于在硅胶存在的情况下通过蒸发线性二肽的环化制备对称和非对称的2,5-二氧吡咯烷。
Efficient Microwave Assisted Syntheses of 2,5-Diketopiperazines in Aqueous Media
Aqueous in situ one-pot N-Boc-deprotection-cyclization of N alpha-Boc-dipeptidyl-tert-butyl and methyl esters under microwave irradiation afforded 2,5-diketopiperazines (DKPs) in excellent yields. This protocol is rapid, safe, environmentally friendly, and highly efficient, and showed that the tert-butoxy moiety is also an excellent leaving group for these cyclizations.
Optically pure diketopiperazines were obtained in good yields when dipeptide esters were refluxed in 2-butanol containing 0.1 M acetic acid for 3 hours. When prolyl-amino acid ester was used as the starting material, 1 to 2 M acetic acid was the most effective concentration.
Studies towards complex bridged alkaloids: regio- and stereocontrolled enolate chemistry of 2,5-diketopiperazines
作者:Mark Pichowicz、Nigel S. Simpkins、Alexander J. Blake、Claire Wilson
DOI:10.1016/j.tet.2008.02.020
日期:2008.4
N-protected diketopiperazines (DKPs) via enolate intermediates has been studied. The enolate reactions were highly diastereocontrolled, leading to enantiopure DKP products if chiral amino acid precursors were employed, and giving racemic products, starting with centrosymmetric DKPs, even when a chiral lithium amide base was used to generate the lithium enolate. With unsymmetrical DKPs derivedfrom proline
Several cyclic dipeptides were synthesized by refluxing methanolic solution of dipeptide methyl esters in high yield and purity. Cyclic dipeptides prepared by the Fischer method, the Nitecki method, and the present methanol-reflux method were compared with respect to yield and optical purity. The methanol-reflux method usually gave good results. High-performance liquid chromatography was effectively applied to detect racemization.