COMMUNICATIONSwere assigned. From the chemical shifts and the coupling constants of 2.5 Hz, 17-H, 18-H, and 19-H were assigned to the protons of a pyrrole ring. This pyrrole ring carries the octatetraenyl and bromo substituents in the 2-and 3-positions, respectively. as confirmed by the chemical shifts in the 13C spectrum and by the COLOC spectrum (COLOC = correlation by longrange couplings). This substitution pattern is also apparent from the strong NOES (NOE = nuclear Overhauser enhancement effect) between 19-H and 13-H/18-H, and between 17-H and 18-H. The remaining C,H,O, fragment is a 4-hydroxy-2pyrone. which is connected to the octatetraenyl residue at C-6, and carries a methyl group in the 3-position. This assignment was contirmed by the COLOC spectrum and by a strong NOE between 5-H and 7-H. Keronopsin B, therefore has structure lc, and is present predominantly in the conformation depicted.From the isotope pattern of the M f signal in the FD mass spectrum ( m / z : 456/454/452), keronopsin B, (Id) contains a second bromine atom. This is found at C-17, since the ' H and I3C N M R spectra of the two compounds were identical, apart from the absence of the 17-H signal. The same is true for keronopsins A , ( l a ) and A, (Ib), which also have one and two bromo substituents, respectively, at C-16 and C-17 of the pyrrole ring. Keronopsins A and A, differ from B, and B, only in the pyrone ring. The signal for the 4-hydroxy group is missing, the signal for 5-H is shifted by A6 = 0.6 downfield, and the signal for C-3 is moved by AS = 5 downfield-the signals for C-2 and C-4 are shifted by A6 = 4-6 upfield, which suggests the presence of a 4-acyloxy substituent. From elemental analysis and negative-