Total synthesis of (–)-spinosyn A

A convergent, highly stereoselective total synthesis of (–)-spinosyn A (1) is described. Key features of the synthesis include the transannular Diels–Alder reaction of macrocyclic pentaene 11 and the transannular Morita–Baylis–Hillman cyclization of 12 that generates tetracycle 26. The total synthesis of (–)-spinosyn A was completed by a sequence involving the highly β-selective glycosidation reaction of 13 and glycosyl imidate 30

Total Synthesis of (+)-Yohimbine via an Enantioselective Organocatalytic Pictet–Spengler Reaction

The binolphosphoric acid-catalyzed Pictet-Spengler reaction of an N-(5-oxy-2,4-pentadienyl)tryptamine derivative with methyl 5-oxo-2-(phenylseleno)pentanoate leads to the tetrahydro-β-carboline in a 92:8 enantiomeric ratio. This product is easily converted into the substrate for a stereoselective intramolecular Diels-Alder reaction of the type earlier reported by Jacobsen. These two key steps constitute the basis for a nine-step total synthesis of (+)-yohimbine from tryptamine. A similar asymmetric Pictet-Spengler reaction was applied to the synthesis of an intermediate in the recent total synthesis of corynantheidine by Sato