Two alkaloids, first isolated from the bark of Acronychia haplophylla by McRwan as alkaloid R (C₁₇H₁₇NO₃) and alkaloid C (C₁₇H₁₉NO₄), have been named acrophylline (II) and acrophyllidine (III) respectively and identified as new furoquinolones based on evidence including spectral data (IR, UV, NMR, mass spectrum), reduction reactions (yielding tetrahydro and hexahydro derivatives), synthesis of hexahydroacrophylline (confirming structure), and acid-catalyzed hydration of acrophylline to acrophyllidine. These are the first recorded examples of (a) naturally occurring 4-furo[2,3-b]quinolones and (b) furoquinoline type alkaloids containing N-isoprenoid groups.