Total Synthesis of Aurantoside G, an N-β-Glycosylated 3-Oligoenoyltetramic Acid from Theonella swinhoei.
The first synthesis of a natural N-glycosylated 3-acyltetramic acid is reported. Aurantoside G (1 g), a deep-red metabolite of the marine sponge Theonella swinhoei, is highly delicate in the pure state. It features a chlorinated dodecapentaenoyl side chain at an l-asparagine-derived tetramic acid, the ring nitrogen atom of which is linked to a β-configured d-xylose. The side chain was built through consecutive Wittig and HWE reactions and used to N-acylate the amino group of an asparaginate that had already been N-xylosylated through a Fukuyama-Mitsunobu reaction. This N-acylation step fixes the β-configuration of the xylose, which is essential for the antifungal activity, but only if the sugar carries bulky, electron-rich protecting groups such as PMB. In the final step, the heterocycle was closed quantitatively through a basic Lacey-Dieckmann condensation of an entirely unprotected precursor.
Organic Chemistry Laboratory, University Bayreuth, Universitaetsstr. 30, 95447, Bayreuth, Germany.
Markus
M
Petermichl
Organic Chemistry Laboratory, University Bayreuth, Universitaetsstr. 30, 95447, Bayreuth, Germany.
Sebastian
S
Loscher
Organic Chemistry Laboratory, University Bayreuth, Universitaetsstr. 30, 95447, Bayreuth, Germany. Rainer.Schobert@uni-bayreuth.de.
Rainer
R
Schobert
D000818:Animals; D006027:Glycosides / Q000138:chemical synthesis* / Q000737:chemistry; D006031:Glycosylation; D008968:Molecular Conformation; D011760:Pyrrolidinones / Q000138:chemical synthesis* / Q000737:chemistry; D047232:Theonella / Q000737:chemistry*
D006027:Glycosides; D011760:Pyrrolidinones; C498132:aurantoside G
aurantosides; glycoconjugates; natural products; tetramic acids; total synthesis