{"title":"Serine-containing 10-membered cyclodepsipeptides. Synthesis and molecular structure of PhCH2CO-DSer-Pro-Pro- and PhCH2CO-DSer-Pro-DPro-.","authors":"S Cerrini, E Gavuzzo, G Luisi, F Pinnen","doi":"","DOIUrl":null,"url":null,"abstract":"<p><p>As a part of a research program aimed at studying synthesis and conformation of small ring peptides, the cyclization of diastereoisomeric N-phenylacetyl-seryl-propyl-proline tripeptides has been examined. Two 10-membered peptide lactones, PhCH2CO-DSer-Pro-Pro- 5a and PhCH2CO-DSer-Pro-DPro- 5b, have been isolated by treating the corresponding linear p-nitrophenyl esters with DBU in dry benzene. In these two compounds the serine lactone fragment (a common structural feature of several bioactive cyclodepsipeptides) is inserted into a highly strained small ring system. The conformation in the crystal of 5a and 5b has been studied by X-ray analysis. Both the 10-membered rings of 5a and 5b adopt an overall cis-cis-trans conformation in which the lactone junction is trans. The deviations from planarity of the peptide units vary from delta omega = 30 degrees for the DSer-Pro bond in 5b to delta omega = 5-6 degrees for the DSer-Pro bond in 5a and Pro-DPro bond in 5b. The skeletal atoms of 5b, containing the Pro-DPro sequence, are related by a pseudo-symmetry mirror plane passing through the Pro carbonyl and the opposite DSer C beta H2 group. In both the molecules the exocyclic amide bond adopts an extended conformation with respect to the DSer-Pro ring junction; this arrangement gives rise to a C5-type ring structure which is well evidenced in the case of 5a.</p>","PeriodicalId":14204,"journal":{"name":"International journal of peptide and protein research","volume":null,"pages":null},"PeriodicalIF":0.0000,"publicationDate":"1993-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"International journal of peptide and protein research","FirstCategoryId":"1085","ListUrlMain":"","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 0
Abstract
As a part of a research program aimed at studying synthesis and conformation of small ring peptides, the cyclization of diastereoisomeric N-phenylacetyl-seryl-propyl-proline tripeptides has been examined. Two 10-membered peptide lactones, PhCH2CO-DSer-Pro-Pro- 5a and PhCH2CO-DSer-Pro-DPro- 5b, have been isolated by treating the corresponding linear p-nitrophenyl esters with DBU in dry benzene. In these two compounds the serine lactone fragment (a common structural feature of several bioactive cyclodepsipeptides) is inserted into a highly strained small ring system. The conformation in the crystal of 5a and 5b has been studied by X-ray analysis. Both the 10-membered rings of 5a and 5b adopt an overall cis-cis-trans conformation in which the lactone junction is trans. The deviations from planarity of the peptide units vary from delta omega = 30 degrees for the DSer-Pro bond in 5b to delta omega = 5-6 degrees for the DSer-Pro bond in 5a and Pro-DPro bond in 5b. The skeletal atoms of 5b, containing the Pro-DPro sequence, are related by a pseudo-symmetry mirror plane passing through the Pro carbonyl and the opposite DSer C beta H2 group. In both the molecules the exocyclic amide bond adopts an extended conformation with respect to the DSer-Pro ring junction; this arrangement gives rise to a C5-type ring structure which is well evidenced in the case of 5a.