The structures and absolute configurations of seven isomeric alkaloids, (-)-isoelaeocarpiline (1), (+)-elaeocarpiline (2), and five new alkaloids (3,4,5,6, and 7) from Elaeocarpus sphaericus have been determined. The structure of (-)-isoelaeocarpiline (1) and the structure of (+)-elaeocarpiline (2) apart from the relative configuration at C-16, have previously been reported when these alkaloids were isolated from Elaeocarpus dolichostylis. The absolute configuration (7R,8S,9S,16S) of (1), now obtained as the major alkaloid from E. sphaericus (Gaertn.) K. Schum., has been determined by oxidation of (1) with aqueous KMnO4 to S-(-)-methylsuccinic acid, the absolute configuration of which corresponds to that of C-16 in (1). Dehydrogenation of (1) over Pd/C in benzene gives a mixture of 7R,8S,9S-(-)-isoelaeocarpine, [α]D -120° (CHCl3) and 7R,8S,9S,16S-(-)-dihydroisoelaeocarpiline, [α]D -219° (CHCl3). A third alkaloid, C16H21NO2, (+)-epi-isoelaeocarpiline (3) m.p. 90-100°, [α]D +340° (CHCl3), M+ 259, has spectroscopic properties closely similar to those of (1) with the exception of the chemical shift of 16-Me [δ 0.99 compared with δ 0.85 in the spectrum of (1)]. Dehydrogenation of (3) over Pd/C gives a mixture of 7S,8R,9R-(+)-isoelaeocarpine, [α]D +108° (CHCl3) and 7S,8R,9R,16S-(+)-dihydroepi-isoelaeocarpiline, [α]D +140° (CHCl3). As the n.m.r. spectrum indicates that the relative configuration at C-16 is opposite to that of (1), the absolute configuration of (3) can be represented by 7S,8R,9R,16S. The close similarity between the o.r.d. spectra of (+)-elaeocarpiline (2) and (+)-epi-isoelaeocarpiline (3) and of dihydro-(2) and dihydro-(3) indicates that the C-16 and C-8 asymmetric centres, which are associated with the absorbing chromophores, have the same absolute configuration. From previous work the configuration at the C-7, C-8, and C-9 centres of (2) was known to be 7-H,8-H trans-diaxial, 8-H,9-H trans-diaxial, and the absolute configuration of (2) can therefore be represented by 7R,8R,9R,16S. Dehydrogenation of (2) over Pd/C gives a mixture of 7R,8R,9R-(+)-elaeocarpine, [α]D +206° (CHCl3) and 7R,8R,9R,16S-(+)-dihydroelaeocarpiline, [α]D +317° (CHCl3). The fourth alkaloid, (-)-epielaeocarpiline (4), m.p. 70-74°, [α]D -396° (CHCl3), C16H21NO2, M+ 259, has spectral properties closely similar to those of (2) except in the chemical shift of 16-Me [δ 0.85 compared with δ 0.95 for (2)]. Dehydrogenation over Pd/C gives a mixture of 7S,8S,9S-(-)-elaeocarpine, [α]D -210° (CHCl3), and 7S,8S,9S,16S-(-)-dihydroepielaeocarpiline, [α]D -318° (CHCl3). The relative stereochemical difference at C-16 then indicates the absolute configuration 7S,8S,9S,16S for (4). The fifth alkaloid, (+)-epialloelaeocarpiline (5), C16H21NO2, m.p. 130-137°, [α]D +139° (CHCl3), M+ 259, has a dienone chromophore [λmax (EtOH) 326 nm (ε 8150), 239 nm (ε 5430), and 228 nm (ε 5630), and signals from two double-bond protons at δ 5.82 and δ 6.25]. A three-proton doublet at δ 0.94 confirms the presence of the 16-Me, and a broad multiplet at δ 4.22 (7-H) indicates that 7-H,8-H are trans-diaxial. Dehydrogenation over Pd/C gives a complex mixture of four components from which 7S,8R,9R-(+)-isoelaeocarpine has been isolated, and when (5) is chromatographed on silica-gel t.l.c. plates, isomerization occurs to give a mixture of (5) and 7S,8R,9R,16S-(+)-epi-isoelaeocarpiline (3). The apparently anomalous situation that (5) with a broad multiplet for 7-H typical of trans-diaxial 7-H,8-H is converted into (3) with a cis-BC ring junction can be explained by the formulation of (5) as the C-8 epimer of (3). Inspection of molecular models indicates that (5) would assume a preferred conformation with a cis-CD ring junction. Its conversion into (3) can proceed by enolization and epimerization at C-8 with a subsequent chair-to-chair inversion of ring C that changes the CD ring junction from cis to trans and requires inversion of the nitrogen configuration. The sixth alkaloid, (-)-alloelaeocarpiline (6), has not been obtained entirely free from all other isomers. The n.m.r. spectrum is closely similar to that of (+)-epialloelaeocarpiline (5) except in the chemical shift of 16-Me (δ 0.89). Chromatography on silica-gel t.l.c. plates gives a mixture of (6) and (-)-isoelaeocarpiline (1), [α]D -400° (CHCl3), and by the same arguments used to explain the epimerization of (5) at C-8, (6) must be the C-8 epimer of (1) with a cis-CD ring junction. The absolute configuration of (6) can therefore be represented as 7R,8R,9S,16S. The seventh alkaloid, (+)-pseudoepi-isoelaeocarpiline (7), [α]D +222° (CHCl3), C16H21NO2, M+ 259, has not been obtained crystalline but gives a crystalline picrate, m.p. 230-235° (decomp.). Alkaloid (7) has an α,β-unsaturated carbonyl group [λmax (EtOH) 275 nm (ε 7600)], and hydrogenation over PtO2 gives 7S,8R,9R,16S-(+)-dihydroepiisoelaeocarpiline. The n.m.r. spectrum of (7) is similar to that of (3) with a narrow multiplet at δ 4.55 (7-H) and a three-proton doublet at δ 1.13 (16-Me). The signals from the double-bond protons of (7) are different, however, and can be analysed as a pair of AB doublets with small vicinal and allylic couplings consistent with a C-14,C-15 double bond (δ 5.53 (H-14), δ 5.74 (H-15), J14,15 10 Hz, J13,14 4 Hz, J15,16 4 Hz). The absolute configuration (7S,8R,9R,16S) is therefore the same as in (3).