Synthesis of (−)-chanoclavine I

✍ Scribed by Nathalie Kardos; Jean-Pierre Genet

• Book ID: 103977023
• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 743 KB
• Volume: 5
• Category: Article
• ISSN: 0957-4166
• DOI: 10.1016/0957-4166(94)80122-3

✦ Synopsis

We then focused our attention on the asymmetric formation of the CT-Cl0 bond of the nitro acetate 3 using paRadium xero complexes 23 . The best results of this key cyclisation were obtained by using Pd(dba)g and (S,S)-CHIRAPHOS as the chiral diphosphine, in THF at teflux I8 . We optimised these results by employing W(OAch and (S)-(-)-BINAP in THF at room temperature. The desired enrmtiomer (5R) is obtained under these mild conditions with 60% yield, and diastereo-and enantiostereoselectivity of up to 95% 23 (scheme 3). This increase ofdiaatemo-and enantioselectivity can be rational&d by the ligand pocket effect 2~. With BINAP, the electtophilic allyl-palladium complex is a seven membered ring. The sterlc effects cause an increase of the asymmetric induction. This reaction was carried out without any protection of the indolic nucleus. It represents a convenient method for creating such tricyclic nitro compotmd, which is a good ptecursor oft&y& ergot alkaloids.