We have previously reported the isolation from Aphis nerii of the polyketide glucosides neriaphin (I), 6-hydroxymusizin-8-O-β-D-glucoside (IV), glucoside B (VIII), fluoraphin (X), and acetylfluoraphin (XI). An additional small fraction of the polar pigments in the aphid extract was shown by NMR spectrometry to be a 2:1 mixture of 6'-monoacetyl-glucosides II and V. Repeated chromatography of the acetone extract of a large batch (405 g.) of A. nerii yielded trace amounts of two red-fluorescent compounds, XIII and XIV, which were not reduced by sodium dithionite but gave borohydride reduction products with UV spectra matching glucoside B (VIII). NMR spectra showed they were derived from neriaphigenin (III) and 6-hydroxymusizin (VI) respectively, with modification of the resorcinoid ring, eliminating one aromatic proton, shielding another, and introducing two quaternary C-methyl groups. Mass spectra revealed addition of 68 mass units (biacetyl minus water) to the aglycones, supporting hemiacetal structures (XIII, XIV). Synthesis by condensing biacetyl with aglycones III, VI, and IX (from hydrolysis of I, IV, VIII) produced XIII, XIV, and analog XV, with synthetic XIII and XIV identical to natural ones. Mild acetylation of XIII gave triacetylated product XVI with re-aromatization. The possibility of XIII and XIV being artefacts was eliminated by their presence in fresh extracts and live aphids. These compounds are among the few natural products related to biacetyl rather than normal acetate units.