Synthesis of eupomatilone-6 and assignment of its absolute configuration.
[Reaction: see text]. The Zn-mediated Barbier reaction of the biarylaldehyde 8 with crotyl bromide followed by hydroboration and oxidation provided the gamma-butyrolactones 4 and 5. The stereoselective installation of methyl group at C-3 by using LiHMDS and MeI completed the synthesis of racemic eupomatilone-6 (2) and its diastereomer 3. The spectroscopic data of 2 was in full agreement with reported spectra of natural product, thus confirming the revised relative configuration of eupomatilone-6. Similarly, an optically active (3R,4R,5S)-isomer of eupomatilone-6 (23) was prepared in which the aldol reaction with thiazolidinethione as a chiral auxiliary was employed as a key step. On the basis of the spectroscopic data and optical rotation values of 23, the absolute configuration of eupomatilone-6 was proposed.
Gurjar
Mukund K
MK
National Chemical Laboratory, Dr. Homi Bhabha Road, Pune - 411 008, India. mk.gurjar@ncl.res.in
Karumudi
Bhargava
B
Ramana
C V
CV
D001572:Benzofurans / Q000138:chemical synthesis* / Q000737:chemistry; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D008968:Molecular Conformation; D015394:Molecular Structure; D009904:Optical Rotation; D013237:Stereoisomerism
D001572:Benzofurans; C485126:eupomatilone-6