An asymmetric total synthesis of (+)-6-hydroxythiobinupharidine (1b) and (-)-6-hydroxythionuphlutine (2b), a set of hemiaminal containing dimeric sesquiterpenes isolated from yellow water lilies of the Nuphar genus, is described. The central bis-spirocydic tetrahydrothiophene ring was forged through the Stevens rearrangement of a sulfonium ylide, generated in situ from the coupling of a copper-carbene with a spirocydic thietane. This strategy diverges both from the proposed biosynthesis(1) and previous syntheses of this family of alkaloids(,2,3) all of which employ dimerization of symmetric monomers to form the aforementioned thiaspirane. The coupling of unsymmetrical monomers allowed access to the unsymmetrically oxidized product 2b for the first time.