Yohimbine enantioselective synthesis

Lee AWM, Chan WH, Mo T (1996) Chiral acetylenic sulfoxides in enantioselective synthesis Asymmetric synthesis of pentacyclic yohimbine alkaloids. Presented at the 212th American Chemical Society National Meeting, Orlando... 

More recently, Szdntay and co-workers (232) succeeded in performing the enantioselective total synthesis of both natural and unnatural antipodes of yohimbine and -yohimbine. Utilizing second-order asymmetric induction, either the levorotatory or dextrorotatory antipode of key tetracyclic intermediate 400 could be obtained by the use of (—)- or (+)-tartaric acid, respectively. 

Yohimbine alkaloids possess a characteristic pentacyclic indole skeleton. Representative members of the family include the rauwolfia (reserpine and deserpidine) and the yohimbines. A wide range of medicinal properties has been associated with these compounds and extensive studies have been carried out on the synthesis of the yohimbine alkaloids, including enantioselective syntheses [13,14]. In our approach, we view the acetylenic sulfoxide as a two-carbon synthon for the C3-C14 segment of the pentacyclic system (see 27). The chirali-... 

Herle B, Wanner MJ, van Maarseveoi JH, Hiemstra H (2011) Total Synthesis of (+)-Yohimbine via an Enantioselective Organocatalytic Pictet-Spengler Reaction. J Org Chem 76 8907... 

Wanner et al. developed an efficient Pictet-Spengler reaction of secondary amines and aldehydes via the formation of active sulfenyliminium ions in situ from N-sulphenyltryptamine 16, catalyzed by chiral Brpnsted acids 5d (Scheme 2.6b) [9a], The enantioselectivity may be delivered from asymmetric counterion-directed catalysis [9a], Based on a similar strategy, they achieved the total synthesis of (+)-yohimbine via a phosphoric acid-catalyzed Pictet-Spengler reaction, which employed an A -(5-oxy-2,4-pentadienyl)tryptamine derivative and methyl 5-oxo-2(phenylseleno)pentanoate as starting materials [9b],... 

---