A new bishordeninyl terpene alkaloid, O-methylalfileramine [1], was isolated from the MeOH extract of the leaves of Zanthoxylum chiriquinum, along with the already known alfileramine [2], culantraramine [3], and isoalfileramine [4]. This is the first report of the isolation of the two skeleton types of bishordeninyl terpene alkaloids from the same species. Zanthoxylum chiriquinum Standl. (Rutaceae) is a very rare species, but our finding of a few trees in the cloud forest south of San Jose, Costa Rica, has both provided a new location and made material available for this work. At the time of our collection, 'carboneros' were in the area cutting trees and burning them to manufacture charcoal, so this new location may not survive for long. In this note we describe the isolation of the new alkaloid O-methylalfileramine (1). Dry leaves of Z. chiriquinum were extracted, and the alkaloidal fraction was submitted first to Si gel chromatography and then to hplc (normal phase), affording compounds 1-4. Compounds 2-4 were shown by spectroscopic studies and direct comparison with authentic samples to be the known alkaloids alfileramine (2), culantraramine (3), and isoalfileramine (4) (1,2). The small quantity of isoalfileramine [4] isolated might suggest the possibility that this compound is an artifact derived from alfileramine during the acid-base isolation procedure. The new compound, O-methylalfileramine (1), was isolated as an oil that solidified upon standing. It has optical activity as with all bishordeninyl terpene alkaloids isolated so far. The uv spectrum [λ max (EtOH)=283 nm] is coincident with that of a substituted C6H6, and the lack of displacement with base shows that the molecule does not have a phenolic group. The fabms spectrum showed an [MH]+ signal at m/z 477, indicating that the mol wt is 476. The molecular formula was established as C31H44N2O2 by hreims (found 476.3400, calcd 476.3405), and the fragmentation pattern of this compound was found to be very similar to that of alfileramine [2], the most remarkable signals being m/z 476, 474, 418, 246, 244, 230, 229, 185, 173, 159, and 58. The ¹H-nmr spectrum of this alkaloid is also very similar to that of 2, but it does not present the duplicity of signals which characterized 2 as a result of the hindered rotation around the sp²-sp³ bond 5-5' (3). Also, it shows the presence of a methyl singlet at 3.82 δ for an aromatic methoxyl group; this was corroborated by its ¹³C-nmr spectrum, which shows an additional signal at 51.43 δ. These observations allowed us to identify compound 1 as the new alkaloid O-methylalfileramine. The assignment of the ¹H nmr is supported by a 2D COSY experiment. The relative stereochemistry of the three chiral centers was deduced by transformation of 1 (heating in acidic media) to isoalfileramine [4]; the stereochemistry of this compound has been established by X-ray crystallography (4).