Recent research showed that fungal micromycetes isolated from marine sources are interesting as producers of biologically active compounds. A novel ethyl 3(R)-acetamido-3-(4-hydroxyphenyl)propanoate (1), cis-4-hydroxyscytalone (2), and ethyl β-(S)-hydroxybenzopropanoate (3) were isolated from Penicillium thomii KMM 4680, which was isolated from the surface of brown alga Alaria ochotensis collected at Cape Levaya Kleshnya, Brouton Bay, Simushir Island during cruise No. 43 on the RV Academic Oparin, during work on a program to search for biologically active compounds in extracts of marine isolates of microscopic fungi. Compound 2 was previously obtained from the pathogenic fungus Leptosphaeria maculans, and compound 3 was first isolated as a natural compound. Herein we communicate the isolation and structure of 1. The fungus was cultivated on standard rice medium for 21 d at room temperature to produce the metabolite. The fungal mycelium with medium was extracted with EtOAc, and the extract was evaporated under vacuum. The dry residue was chromatographed over a column of silica gel using hexane-EtOAc of increasing polarity, followed by HPLC over a YMC-Pack ODS-AM C18 column using MeOH-H2O (60:40) to yield 1 (2 mg). The molecular formula of 1 was determined as C13H17NO4 by high-resolution electrospray mass spectrometry and confirmed by 13C NMR spectral analysis. The structure was established as ethyl 3-acetamido-3-(4-hydroxyphenyl)propanoate based on PMR, 13C NMR, HSQC, and HMBC data. The R-configuration at the C-3 asymmetric center was proposed by comparing the specific rotation of 1 in CHCl3 with those of the (R)- and (S)-isomers of ethyl 3-hydroxy-3-phenylpropanoate from the literature. Compounds 1–3 at a concentration of 100 μM did not possess cytotoxic activity and did not inhibit colony formation of 22Rv1 human prostate cancer cells.