<?xml version="1.0" encoding="UTF-8"?><?xml-stylesheet type="text/xsl" href="static/style.xsl"?><OAI-PMH xmlns="http://www.openarchives.org/OAI/2.0/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/ http://www.openarchives.org/OAI/2.0/OAI-PMH.xsd"><responseDate>2026-08-22T19:39:19Z</responseDate><request verb="GetRecord" identifier="oai:docta.ucm.es:20.500.14352/133371" metadataPrefix="marc">https://docta.ucm.es/rest/oai/request</request><GetRecord><record><header><identifier>oai:docta.ucm.es:20.500.14352/133371</identifier><datestamp>2026-02-27T00:47:18Z</datestamp><setSpec>com_20.500.14352_14</setSpec><setSpec>col_20.500.14352_15</setSpec></header><metadata><record xmlns="http://www.loc.gov/MARC21/slim" xmlns:dcterms="http://purl.org/dc/terms/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:doc="http://www.lyncode.com/xoai" xsi:schemaLocation="http://www.loc.gov/MARC21/slim http://www.loc.gov/standards/marcxml/schema/MARC21slim.xsd">
   <leader>00925njm 22002777a 4500</leader>
   <datafield ind2=" " ind1=" " tag="042">
      <subfield code="a">dc</subfield>
   </datafield>
   <datafield ind2=" " ind1=" " tag="720">
      <subfield code="a">Caballero, Esmeralda</subfield>
      <subfield code="e">author</subfield>
   </datafield>
   <datafield ind2=" " ind1=" " tag="720">
      <subfield code="a">Avendaño López, María Carmen</subfield>
      <subfield code="e">author</subfield>
   </datafield>
   <datafield ind2=" " ind1=" " tag="720">
      <subfield code="a">Menéndez, J. Carlos</subfield>
      <subfield code="e">author</subfield>
   </datafield>
   <datafield ind2=" " ind1=" " tag="260">
      <subfield code="c">1998</subfield>
   </datafield>
   <datafield ind2=" " ind1=" " tag="520">
      <subfield code="a">The cyclization of all four diastereoisomers of cyclo-(Trp-Ala) to the corresponding 3,5a,6,10b,11,11ahexahydro-2H-pyrazino[20 ,10 -5,1]pyrrolo[2,3-b]indoles is studied from the stereochemical point of view. Epimerization of the tryptophan stereocenter during the cyclization and during acylation reactions of the N-2 atom of the tetracyclic derivatives is discussed.</subfield>
   </datafield>
   <datafield ind1="8" ind2=" " tag="024">
      <subfield code="a">Caballero E, Avendaño C, Menéndez JC. Stereochemical issues related to the synthesis and reactivity of pyrazino[2′,1′-5,1]pyrrolo[2,3-b]indole-1,4-diones. Tetrahedron: Asymmetry. marzo de 1998;9(6):967-81. doi:10.1016/S0957-4166(98)00068-8</subfield>
   </datafield>
   <datafield ind1="8" ind2=" " tag="024">
      <subfield code="a">10.1016/S0957-4166(98)00068-8</subfield>
   </datafield>
   <datafield ind1="8" ind2=" " tag="024">
      <subfield code="a">https://hdl.handle.net/20.500.14352/133371</subfield>
   </datafield>
   <datafield ind1="8" ind2=" " tag="024">
      <subfield code="a">https://dx.doi.org/10.1016/S0957-4166(98)00068-8</subfield>
   </datafield>
   <datafield ind2="0" ind1="0" tag="245">
      <subfield code="a">Stereochemical issues related to the synthesis and reactivity of pyrazino[20 ,10 -5,1]pyrrolo[2,3-b]indole-1,4-diones</subfield>
   </datafield>
</record></metadata></record></GetRecord></OAI-PMH>