Terpenes U 0200Three New Monoterpenoids from the Fruit of Genipa americana. -Genipacetal (I), genipamide (II), and genipaol (III) are isolated from the MeOH extract of the title plant. -(ONO*, M.; ISHIMATSU, N.; MASUOKA, C.; YOSHIMITSU, H.; TSUCHIHASHI, R.; OKAWA, M.; KINJO, J.; IKEDA, T.; NOHARA, T.; Chem.

Genipa americana L. (Rubiaceae) is widely distributed in tropical Central and South America. The fruit of this plant is edible and popular as source of beverages. The white flesh turns yellow to bluish-purple and finally to jet-black on exposure to the air. 1)We earlier reported the isolation and structural elucidation of eight iridoid glucosides from the fruit of G. americana. 2)As part of the continuing study of the constituents of this fruit, we now describe the isolation and structural elucidation of three new monoterpenoids (1-3), along with four known iridoids (4-7) from this fruit.Compounds 4-7 were identified as genipin (4), 3) gardendiol (5), 4) deacetyl asperulosidic acid methyl ester (6), 5) and shanzhiside (7) 6) based on their physical and spectral data, although detailed 1 H-and 13 C-NMR spectral data of 6 and 7 have not been reported in the literature.Compound 1, called genipacetal, was obtained as a colorless syrup and exhibited an [MϩNa] ϩ ion peak at m/z 249 in the positive FAB-MS; the high-resolution (HR) FAB-MS indicated the molecular formula of 1 to be C 11 H 14 O 5 . The C-NMR signals were assigned with the aid of heteronuclear multiplequantum coherence (HMQC) and heteronuclear multiplebond correlation (HMBC) spectra (Tables 1, 2). From the cross-peaks observed in the HMBC spectrum (H-1/C-5, C-8, C-9, and C-10; H-3/C-10 and C-11; H-4/C-3, C-5, C-6, C-9, and C-11; H-5/C-3; H-6/C-3, C-7, C-8, and C-9; H-7/C-5; H-10/C-1 and C-3; and H 3 CO/C-11) the planar structure of 1, which is a monoterpenoid possessing a new skeleton with one methoxycarbonyl group, one five-membered cyclic acetal group, and one five-membered cyclic hemiacetal group, could be suggested (Fig. 1). Ordinary acetylation of 1 with acetic anhydride and pyridine afforded the corresponding monoacetate (1a) rather than triacetate. Comparing the chemical shifts of the signals between 1 and 1a, the signal due to H-1 in 1 was shifted downfield by 0.85 ppm. Thus the presence of a hemiacetal group at C-1 and an epoxy bridge between C-3 and C-10 was established. The relative configurations at the C-5, C-7, C-8, C-9, and C-10 chiral centers were automatically established by forming the epoxy bridge. In the nuclear Overhauser and exchange spectroscopy (NOESY) spectrum of 1, a key NOE was observed between H-1 and H-4; this indicated that the relative configurations at C-1 and C-4 were as shown in Fig. 2. Furthermore, the coupling constant values for the signals in the 1 H-NMR spectrum were analogous to those calculated for the dihedral angles, which was simulated using CAChe CONFLEX, 6) and the Karplus equation 7) (Table 3). Consequently, the structure of 1 was concluded to be as shown in Fig. 3. Three new monoterpenoids, called genipacetal, genipamide, and genipaol, were isolated from the fruit of Genipa americana L. (Rubiaceae), along with the four known iridoids genipin, gardendiol, deacetyl asperulosidic acid methyl ester, and shanzhiside. Their chemical structures were determined on the basis of spectroscopic data.