Suaveoline synthesis

During the enantiospecihc total synthesis of ajmalin-related alkaloids, (-)-suaveoline and (-)-raumacline, N-debenzylation of the hydrochloride salt of the alkaloids was performed with 10% Pd/C (0.12 mol Pd/mol compound) in absolute EtOH at room temperature and 1 atm of hydrogen for 1 or 2 hours. When this catalytic debenzylation was performed, however, using 10% Pd/C (0.28 mol Pd/mol compound) in MeOH for 5 hours, N-methyl derivatives were produced in good yield (Scheme 4.91).339,340... 

Examples of cycloadditions with oxazole substrates that lead to products other than furans are also known. 4-Substituted oxazole 73 has been used in an intramolecular Diels-Alder reaction <2004TL6471> with an alkene to afford a pyridyl cycloadduct 74 in good yields en route to the synthesis of a Rauwolfm alkaloid, (—)-suaveoline. This reaction required refluxing xylene with l,5-diazabicyclo[4.3.0]non-5-ene (DBN) as an additive (Scheme 13). 

An intermediate amide 27 required for the synthesis of alkaloids suaveoline and norsuaveoline is prepared via the coupling of amine 26 and monoethyl malonate in the presence of DEPC.11... 

Total Synthesis of Suaveoline (261) via an Intramolecular Diels—Alder Reaction 157... 

Trudell had originally achieved a total synthesis of ( )-suaveoline from ( )-tryptophan and in 1992 Fu et finished a total synthesis of (—)-sua-... 

Cloudsdale, I. S. Kluge, A. F. McClure, N. L.J. Org. Chem. 1982, 47, 919—928. Soerens, D. A. Part I. Studies of the Pictet—Spengler Reaction in Aprotic Media. Part 11. Studies Directed toward the Total Synthesis of the Indole Alkaloid Suaveoline University of Wisconsin-Milwaukee Milwaukee, WI, 1978. 

---