Reaction of methyl 10-undecenoate (I) with phenylselenyl chloride in acetonitrile furnished methyl 11-phenylseleno-10-acetamido-undecanoate (II) as a major product, and a similar reaction of I with phenylselenyl chloride in absolute ethanol gave ethyl 11-phenylseleno-10-ethoxyundecanoate (III) as a sole product. A similar reaction of methyl octadec-cis-9-enoate (IV; oleate) with phenylselenyl chloride in absolute ethanol was conducted and resulted in the formation of ethyl 10(9)-phenylseleno-9(10)-ethoxy-octadecanoate (V).