A selective 3-acylation of tetramic acids and the first synthesis of ravenic acid.
3-Acyltetramic acids, including delicate 3-oligoenoyl derivatives, such as the Penicillium metabolite ravenic acid, were prepared in two high-yielding steps. Reaction of tetramic acids with the ylide Ph(3)PCCO afforded exclusively the corresponding 3-acylylidenetetramic acids. These were amenable to Wittig olefinations with aliphatic, aromatic, saturated and unsaturated aldehydes after deprotonation with KOtBu. Due to its simplicity, selectivity and tolerance of pH-sensitive groups this method is superior to the established acylation protocols by Jones and Yoshii. It is also applicable to the synthesis of 3-acyltetronic acids. The new 3-oligoenoyl tetramic acids exhibited structure-dependent antimicrobial and cytotoxic activity.
Schlenk
Andrea
A
Organic Chemistry Laboratory, University of Bayreuth, Universitaetsstrasse 30/NW 1, 95440 Bayreuth, Germany.
Diestel
Randi
R
Sasse
Florenz
F
Schobert
Rainer
R
D000215:Acylation; D000447:Aldehydes / Q000737:chemistry; D000475:Alkenes / Q000737:chemistry; D000890:Anti-Infective Agents / Q000737:chemistry* / Q000494:pharmacology; D002384:Catalysis; D011760:Pyrrolidinones / Q000138:chemical synthesis* / Q000737:chemistry* / Q000494:pharmacology*; D013055:Spectrophotometry, Infrared; D013237:Stereoisomerism
D000447:Aldehydes; D000475:Alkenes; D000890:Anti-Infective Agents; D011760:Pyrrolidinones; C470524:ravenic acid; C009435:tetramic acid