~ Pergamon PII: S0031-9422(97)00672-9 Phytochemistry, Vol. 47, No. 6, pp. l 15%1159, 1998 © 1998 Elsevier Science Ltd. All rights reserved Printed in Great Britain 00314422/98 $19.00+0.00 PHLOROGLUCINOL-MONOTERPENE ADDUCTS FROM EUCAL YPTUS GRANDIS INDER PAL SINGH, KAZUHIROUMEHARA,* TATSUO ASAI,* HIDEO ETOH,*~ MIDORI TAKASAKI~ and TAKAO KONOSHIMA~ The United Graduate School of Agricultural Sciences, Gifu University (Shizuoka University), 836 Ohya, Shizuoka 422, Japan ; * Department of Applied Biological Chemistry, Shizuoka University, 836 Ohya, Shizuoka 422, Japan ; t Kyoto Pharmaceutical University, Misasagi, Yamashina-ku, Kyoto 607, Japan (Receivedin revised form 16 June 1997) Key Word Index--Eucalyptus grandis; Myrtaceae; leaves; euglobals-G6 and -G7; phloro- glucinol-monoterpene adducts. Abstract--Two new euglobals, G6 and G7 were isolated from the hexane fraction of the methanol extract of the leaves of Eucalyptus #randis. These have phloroglucinol-monoterpene structures. Both euglobals have a formyl-isovaleroyl phloroglucinol moiety fused with ?-terpinene. Their structures were elucidated on the basis of spectral evidences. © 1998 Elsevier Science Ltd. All rights reserved INTRODUCTION Eucalyptus is a rich source of phloroglucinol com- pounds which exhibit interesting biological activities. In the course of our search for bioactive compounds from natural sources, we have also reported on the presence of several bioactive compounds in Euca- lyptus [1-4]. We have recently isolated a new phloro- glucinol dimer, grandinal, from the chloroform frac- tion of the methanol extract of the leaves of E. yrandis [5]. Further investigations into the hexane fraction led to the isolation of two new euglobals named euglobals G6 and G7. Euglobals G1-G5, also from the leaves of E. grandis, have been reported as inhibitors of Epstein Barr Virus (EBV) activation [6]. In this paper, we report on the structural elucidation of these two new compounds and their inhibitory activity against EBV activation induced by 12-O-tetradecanoyl phorbol- 13- acetate (TPA). RESULTS AND DISCUSSION The hexane fraction of the methanol extract of air- dried leaves ofE. 9randis was fractionated as described in the Experimental section to yield euglobal G6 (1) and G7 (2) in 0.0095 and 0.011% yields, respectively. The high-resolution mass spectra of 1 and 2 revealed the molecular formula as C23H3005. The UV spectra of both compounds were superimposable on those of :~ Author to whom correspondence should be addressed. other euglobals, especially euglobal IIc (3) and eug- lobal-T1 (4) [7]. The high-field 1H NMR spectrum of 1 showed strik- ing similarity with that of euglobal IIc (3) [7]. The 13C NMR and DEPT spectra showed 23 carbons and 28 hydrogens bound to carbon atoms. These NMR spec- tra established that 1 contained a phloroglucinol moiety (6 c 171.6, 168.2, 161.1,103.9, 103.5 and 100.5) containing one aldehyde group (6c 192.0) and one isovaleroyl group [6 c 206.4 (s), 52.7 (t), 25.1 (d), 2 × 22.8 (q)]. The presence of a doublet carbon (6 114.3) and a singlet carbon (6 140.7) in the 13C NMR spectrum and a one proton singlet at 3 5.23 suggested the presence of a trisubstituted double bond instead of the disubstituted double bond in 3 and 4. The structure of the monoterpene part and its linkage to the phloroglucinol unit was elucidated by measuring ~H-~H COSY, HSQC and HMBC as shown in Scheme 1. HMBC correlations from H-7 to carbons at 1, 2 and 6, and from the phenolic group at 6 15.4 (6-OH) to carbons 1, 5 and 6, and from the formyl proton at 6 10.01 to carbons 3 and 4, suggested that the formyl group was located at position 3 and the isovaleroyl group at position 5. This linkage was further con- firmed by differential NOE experiments. Strong through-space interactions were observed between methyl 7' and formyl proton H-8, and between formyl proton H-8 and the phenolic proton at position 4. Also, the phenolic proton at position 6 showed strong through-space interaction with proton H-7. These interactions determined the location of isovaleroyl group at position 5 unambiguously. Other significant HMBC and JH-IH COSY correlations are shown in 1157