<jats:title>Abstract</jats:title><jats:p>Annosqualine (=(10′b<jats:italic>R</jats:italic>)‐1′,5′,6′,10′b‐tetrahydro‐9′‐hydroxy‐7′,8′‐dimethoxyspiro[cyclohexa‐2,5‐diene‐1,2′‐pyrrolo[2,1‐<jats:italic>a</jats:italic>]isoquinoline]‐3′,4‐dione; <jats:bold>1</jats:bold>), a novel alkaloid with an unprecedented skeleton, and a new amide, dihydrosinapoyltyramine (=3‐(4‐hydroxy‐3,5‐dimethoxyphenyl)‐<jats:italic>N</jats:italic>‐[2‐(4‐hydroxyphenyl)ethyl]propanamide; <jats:bold>2</jats:bold>), were isolated from the stems of <jats:italic>Annona squamosa</jats:italic> L., together with six known alkaloids. The structures of all compounds were elucidated spectroscopically by means of optical rotation, <jats:sup>1</jats:sup>H‐, <jats:sup>13</jats:sup>C‐, and 2D‐NMR, and by EI‐MS, or by comparison with the spectral data of authentic samples. A possible biogenetical pathway towards annosqualine (<jats:bold>1</jats:bold>) is proposed.