An eight step, asymmetric synthesis of a dimeric thiaspirane nuphar alkaloid from 3-methyl-2-cyclopentenone is reported. The brevity of the route relies on a useful procedure for tandem reductive allylation of cyclopentenones, as well as the minimization of redox manipulations and other functional group interconversions. The distribution of products that arise from spontaneous dimerization points to a more complex biosynthesis.