Polyphosphoric acid trimethylsilyl ester promoted intramolecular acylation of an olefin by a carboxylic acid: convenient construction of C-18-functionalized delta14-hecogenin acetate.
[reaction: see text]. Polyphosphoric acid trimethylsilyl ester (PPSE)-promoted intramolecular Friedel-Crafts reactions on a nonaromatic carboxylic acid system have been investigated. Studies led to the synthesis of C-18 functionalized steroidal compounds 5 and 9a-d with strict retention of the spiroketals. Isomerization of spiroketal 9e was studied.
Li
Wei
W
Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, USA.
Fuchs
Philip L
PL
D000215:Acylation; D000475:Alkenes / Q000737:chemistry*; D002264:Carboxylic Acids / Q000737:chemistry*; D007536:Isomerism; D015394:Molecular Structure; D010756:Phosphoric Acids / Q000737:chemistry*; D017553:Phosphorus Compounds / Q000737:chemistry; D011108:Polymers / Q000737:chemistry*; D012502:Sapogenins / Q000737:chemistry*; D012833:Siloxanes / Q000737:chemistry; D013141:Spiro Compounds / Q000737:chemistry; D014297:Trimethylsilyl Compounds / Q000737:chemistry*
D000475:Alkenes; D002264:Carboxylic Acids; D010756:Phosphoric Acids; D017553:Phosphorus Compounds; D011108:Polymers; D012502:Sapogenins; D012833:Siloxanes; D013141:Spiro Compounds; D014297:Trimethylsilyl Compounds; C007908:hecogenin; C012500:phosphorus pentoxide; C047269:polyphosphoric acid; C015917:hexamethyldisiloxane