C-24 stereochemistry of marine Sterols: (22E)-24-Ethyl-24-methylcholesta-5,22-dien-3b-oβl and 24-Ethyl-24-methylcholest-5-en-3β-ol
| Autor: | Yoshinori Fujimoto, Carmenza Duque, Noriyuki Hara, Leonardo Castellanos, Hidehiro Uekusa, Shizue Echigo |
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| Rok vydání: | 2011 |
| Předmět: |
orthoester Claisen rearrangement
marine sterol Stereochemistry Carbon-13 24-ethyl-24-methylcholesterol 24-ethyl-24-methylcholesta-5 22-dien-3b-ol General Chemistry Topsentia ophiraphidites Nmr data NMR spectra database Claisen rearrangement chemistry.chemical_compound Stereospecificity chemistry Yield (chemistry) Orthoester |
| Zdroj: | Journal of the Brazilian Chemical Society v.22 n.5 2011 Journal of the Brazilian Chemical Society Sociedade Brasileira de Química (SBQ) instacron:SBQ Journal of the Brazilian Chemical Society, Volume: 22, Issue: 5, Pages: 1004-997, Published: MAY 2011 |
| ISSN: | 0103-5053 |
| DOI: | 10.1590/s0103-50532011000500026 |
| Popis: | The C-24 configurations of (22E)-24-ethyl-24-methylcholesta-5,22-dien-3β-ol (1) and 24-ethyl-24-methylcholest-5-en-3β-ol (2), isolated from the Colombian Caribbean sponge Topsentia ophiraphidites, were determined to be R and S, respectively, by comparing their NMR data with those of stereodefined (24R)- and (24S)-samples that were synthesized in routes involving the orthoester Claisen rearrangement of Δ23-22-allylic alcohols. This is the first synthetic study where the Claisen rearrangement is used to introduce a C-24 quaternary center in a stereospecific manner with acceptable yield. X-ray analysis of 1 confirmed these stereochemical assignments. As configurações dos carbonos C-24 nos compostos (22E)-24-etil-24-metilcolesta-5,22-dien-3β-ol (1) e 24-etil-24-metilcolest-5-en-3β-ol (2), isolados da esponja do caribe colombiano Topsentia ophiraphidites foram determinadas como R e S, respectivamente, com base na comparação dos seus dados de RMN com aqueles de amostras de configurações já definidas 24R e 24S, as quais foram sintetizadas em rotas envolvendo ortoésteres provenientes do rearranjo de Claisen de álcoois Δ23-22 alílicos. Este é primeiro estudo de síntese, em que o rearranjo de Claisen é utilizado para introduzir um centro quaternário em C-24, de maneira estereoespecífica e com rendimento aceitável. Análises por difração de raio X de 1 confirmaram essas atribuições estereoquímicas. |
| Databáze: | OpenAIRE |
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