3′,4′,5′,6′-Tetradehydrolongicaudatine Y, an anhydronium base from Strychnos usambarensis - Frederich,M.; Quetin-Leclercq,J.; Gadi-Biala,R.; Brandt,V.; Penelle,J.; Tits,M.; Angenot,L. (Phytochemistry, 1998)