A 9-Hydroxyiridoid Isolated fromJunellia seriphioides (Verbenaceae)Henrik Franzyk,† Søren Rosendal Jensen,*,† Carl Erik Olsen,‡ andJuan Marcelo Quiroga§

Department of Organic Chemistry, The Technical UniVersity of Denmark,DK-2800, Lyngby, Denmark, Department of Chemistry, The Royal Danish Agriculturaland Veterinary UniVersity, DK-1871 Frederiksberg C, Denmark, and Centro NacionalPatagonico, CONICET, 9120 Puerto Madryn, Chubut, Argentina

oksrj@pop.dtu.dk

Received January 14, 2000

ABSTRACT

An unusual iridoid glucoside, namely 9-hydroxy-8-epihastatoside (1), was isolated from Junellia seriphioides (Verbenaceae), together with theknown compounds auroside (2), pulchelloside I (3), and 8-epihastatoside (4) as well as verbascoside.

Junellia seriphioides(Gillies & Hook.) Moldenke (Verben-aceae) belongs to the dryland vegetation in Northern Pat-agonia; it has been used in traditional medicine byTehuelches Amerindians since pre-Hispanic times. Previouschemical work on this genus comprises only an investigationof the nectar composition.1 We have now studied the polarconstituents of the plant.

The water-soluble part of the ethanolic extract wassubmitted to reverse phase chromatography with H2O-MeOH mixtures as eluents. This gave four iridoid glucosides(1-4) as well as verbascoside. Compounds2-4 wereidentified as auroside,2 pulchelloside I,3 and 8-epihastatoside,4

respectively, by comparison with published NMR data.Compound1 was obtained as a glass [R]21

D ) -246° (c0.5; MeOH) and the FAB MS ofm/z 443 [M + Na]+

corresponded to the formula C17H24O12. The 13C NMRspectrum showed 17 peaks of which 6 could be assigned toa â-glucopyranosyl moiety. The chemical shifts of the

remaining 11 peaks indicated an iridoid aglucone, and thepresence of a carbonyl signal (δ 214.3) suggested a structuresimilar to that of 8-epihastatoside (4) also present in the plant.Comparison with the spectrum of this showed a good overallsimilarity, except that1 contained a hydroxyl-bearing,quaternary carbon atom not seen in4. The1H NMR spectrumshowed the presence of a proton at C-8 in1 since the 10-CH3 peak appeared as a doublet (J ) 7 Hz), and theremaining part was also otherwise very similar to that of4.This left us with the only possibility of assigning thequaternary hydroxyl-bearing carbon atom as C-9, thusleading to the structure1 for the new compound. HSQC andHMBC spectra allowed assignment of all signals in the NMRspectra (Table 1). In particular, the HMBC spectrum provedthe low-field position of C-9 since a strong three-bondinteraction was seen between the signal atδ 75.8 and thatof the 10-methyl group.

† Technical University of Denmark.‡ The Royal Danish Agricultural and Veterinary University.§ Centro Nacional Patago´nico, Argentina.(1) Bernadello, G.; Galetto, L.; Forcone, A.Biochem. Syst. Ecol.1999,

27, 779.(2) Junior, P.Planta Med.1985, 51, 229.(3) Bianco, A.; Caciola, P.; Guiso, M.; Iavarone, C.; Trogoli, C.Gazz.

Chim. Ital. 1981, 201.(4) Foderato, T. A.; Stermitz, F. R.Phytochemistry1992, 31, 4191.

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10.1021/ol0055521 CCC: $19.00 © 2000 American Chemical SocietyPublished on Web 02/04/2000

Assuming the usual iridoid glucoside configuration at C-1,C-5, and C-9, only the stereochemistry at C-8 remained tobe determined. The co-occurrence of1 with 2-4 in the plant,and the possibility of4 being the immediate precursor of1,suggested the 8R-configuration shown. However, in a fewcases members of both epimeric series can be present in thesame plant as seen in somePenstemonspecies4 and also inVerbena,5 a genus closely related toJunellia. Consequently,we had to solve this problem. It has earlier been shown thatan NOE between H-8 and H-1 cannot be used as proof ofthe configuration at C-8 due to conformational shifts in thecyclopentane ring when going from one epimer to theother.6,7 The chemical shift of C-9 is in many iridoid

glucosides indicative of the stereochemistry at C-8,8 but thisis limited to compounds where both these carbon atoms carrya proton, which was not the case here. Also, directcomparison of the13C NMR spectrum of1 with those5,7 of4 and its 8-epimer, hastatoside (5), was not conclusive dueto lack of similar model compounds. The1H NMR dataproved more useful. In both4 and5 the coupling constantJ8,9 has a large value (ca. 10 Hz, Table 1), demanding thedihedral angle∠8,9 to be either ca. 180° or ca. 0.° Molecularmodels showed that a conformational change in the cyclo-pentane ring was necessary to obtain such angles when goingfrom 4 to 5. Thus, an8E-like conformation was necessaryin the former and an E8-like conformation in the latter,respectively. This would allow both conformers to have apseudoequatorial methyl group and a pseudoaxial proton atC-8, consistent with the measured coupling constants. TheJ7,8 coupling constants measured for1 (Table 1) were verysimilar to those seen for both4 and 5. Therefore, 1presumably assumes a conformation similar to one of them.Upon comparison of the shift values from the two protonsat C-7 in the spectrum of1 (δ 2.56 and 2.25) with those of4 (δ 2.50 and 2.23), they were found to be almost identical.Conversely, the corresponding values for5 (δ 2.74 and 1.91)differed considerably. Consequently, we conclude that thenew compound is 9-hydroxy-8-epihastatoside.

9-Hydroxy-substituted iridoid glucosides are very rare. Sofar, a few have been reported fromGelsemium,9 but theseare all atypical with the glucosyl moiety at either the 3- orat the 7-position. Thus1 is the first ordinary iridoid glucosidewith a 9-substituent among the more than 1000 differentcompounds so far published.

Acknowledgment. We thank Dr. Alejandro Bisigato,Centro Nacional Patago´nico, for identifying the plant mate-rial.

Supporting Information Available: Experimental de-tails. This material is available free of charge via the Internetat http://pubs.acs.org.

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(5) Miltz, S.; Rimpler, H.Z. Naturforsch.1979, 34c, 319.(6) Franzyk, H.; Jensen, S. R.; Stermitz, F. R.Phytochemistry1998, 49,

2025.

(7) Franzyk, H.; Jensen, S. R.; Thale, Z.; Olsen, C. E.J. Nat. Prod.1999,62, 275.

(8) Damtoft, S.; Jensen, S. R.; Nielsen, B. J.Phytochemistry1981, 20,2717.

(9) Jensen, S. R.; Kirk, O.; Nielsen, B. J.Phytochemistry1987, 26, 1725.

Table 1. 13C NMR (75 MHz) and1H NMR (500 MHz) Datafor 1 and the Model Compounds4 and5

1 4 5

atom δC δH δH δH

1 96.6 5.70, s 5.95, s 5.92, d(1.5)3 157.5 7.72, s 7.75, s 7.74, s4 107.55 75.46 214.37a 39.5 2.56, dd 2.50, dd 2.74, dd

(17.6, 9.6) (18.3, 8.6) (18.4, 9.3)7b 2.25, dd 2.23, dd 1.93, dd

(17.6, 7.0) (18.3, 6.9) (18.4, 8.4)8 36.2 2.39, m 2.62, m 1.97, m9 75.8 2.72, d 2.23, dd

(10.3) (10.2, 1.5)10 17.7 1.13, d(7.2) 1.01, d(6.9) 1.11, d(6.4)11 168.0Me 53.1 3.66, s 3.65, s 3.64, s1′ 100.5 4.73, d(8) 4.75, d(8) 476, d(8)2′ 73.4 3.29, dd 3.24, dd 3.25, dd3′ 76.4 3.46, t 3.46, t 3.45, t4′ 70.6 3.37, t 3.35, t 3.36, t5′ 77.3 3.44, m 3.45, m 3.46, m6′ 61.5 3.86, dd 3.89, dd 3.87, dd

3.69, dd 3.67, dd 3.68, dd

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