Dictyodendrins A-E, the First Telomerase-Inhibitory Marine Natural Products from the Sponge Dictyodendrilla verongiformis 1 Kaoru Warabi, † Shigeki Matsunaga, † Rob W. M. van Soest, ‡ and Nobuhiro Fusetani* ,† Laboratory of Aquatic Natural Products Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan, and Institute for Systematics and Ecology, University of Amsterdam, 1090 GT Amsterdam, The Netherlands anobu@mail.ecc.u-tokyo.ac.jp Received December 3, 2002 Five new alkaloids, dictyodendrins A-E(1-5), were isolated from the Japanese marine sponge Dictyodendrilla verongiformis as telomerase inhibitors. Their structures were elucidated by spectroscopic and chemical methods. Dictyodendrins are tyramine-based pyrrolocarbazole derivatives containing three or four p-hydroxybenzene groups. They inhibited telomerase completely at a concentration of 50 µg/mL. Telomerase is a ribonucleoprotein enzyme that adds repeats of the DNA sequence, TTAGGG, called telomeres, onto the 3′′-ends of chromosomes. 2-4 Telomerase activity is found in about 90% of human tumors, but not in normal cells. 5 Thus, inhibitors of telomerase are potential antitumor agents. 6-8 In fact, some synthetic inhibitors based on the function of telomerase have been successful in clinical trials. 9 It should be noted that several natural products have been reported to inhibit telomerase, 10,11 but no telomerase-inhibitory marine natural products are known to date. In our screening for anti-telomerase activity of the extracts of Japanese marine invertebrates, the marine sponge Dictyodendrilla verongiformis col- lected in southern Japan showed significant activity. Bioassay-guided fractionation led to the isolation of dictyodendrins A-E (1-5, respectively). This paper describes the isolation and structure elucidation of dic- tyodendrins. Results and Discussion Frozen sponge (80 g, wet weight) was successively extracted with MeOH, EtOH, and acetone. The extracts were combined, concentrated, and partitioned between water and CHCl 3 . The aqueous layer was further ex- tracted with n-butanol, and the active n-butanol layer was separated by ODS flash chromatography with aque- ous methanol followed by gel filtration on Sephadex LH- 20 with methanol. The active fractions were finally purified by reverse-phase HPLC to afford dictyodendrins A(1, 12.8 mg), B (2, 0.9 mg), C (3, 4.6 mg), D (4, 1.5 mg), and E (5, 2.7 mg) along with two known compounds, 6 (21.8 mg) and 7 (1.5 mg), which were isolated as aldose reductase inhibitors from a marine sponge of the same genus. 12 Dictyodendrin A (1) was isolated as a red amorphous solid exhibiting UV-vis absorptions at 328 and 480 nm. Its molecular formula was established as C 43 H 33 N 2 O 11 - SNa on the basis of HR-FABMS and NMR data. IR bands at 3400 and 1724 cm -1 suggested the presence of hydroxyl and ester moieties, respectively. The 1 H NMR spectrum exhibited 13 signals between 5.9 and 7.5 ppm, in addition to signals for a methine, two methylenes, and an O- methyl. Some of the signals were extremely broadened, which indicated the presence of a conformational equi- librium. Interpretation of COSY data led to three pairs of mutually coupled 2H-signals ascribable to 1,4-disub- stituted benzene rings: ring E, δ 7.40 [H-18 (H-22)] and 6.96 [H-19 (H-21)]; ring F, 6.23 [H-26 (H-30)] and 6.48 [H-27 (H-29)]; and ring H, 7.03 [H-39 (H-43)] and 6.71 [H-40 (H-42)]. There was another set of signals attribut- * Corresponding author. † Laboratory of Aquatic Natural Products Chemistry and Graduate School of Agricultural and Life Sciences. ‡ Institute for Systematics and Ecology. (1) Bioactive Marine Metabolites 117. Part 116: Nakao, Y.; Yoshida, S.; Matsunaga, S.; Fusetani, N. Submitted for publication. (2) Blackburn, E. H. Cell 2002, 106, 661-673. (3) Cech, T. R. Angew. Chem., Int. Ed. 2000, 39, 34-43. (4) Maser, R. S.; Depinto, R. A. Science 2002, 297, 565-569. (5) Lavelle, F.; Riou, J.-F.; Laoui, A.; Mailliet, P. Crit. Rev. Oncol. Hematol. 2000, 34, 111-126. (6) White, L. K.; Wright, W. E.; Shay, J. W. Trends Biotechnol. 2001, 19, 114-120. (7) Neidle, S.; Parkinson, G. Nat. Rev. Drug Discov. 2002, 1, 383- 393. (8) Helder, M. N.; Wisman, G. B. A.; van der Zee, A. G. J. Cancer Invest. 2002, 20, 82-101. (9) Gowan, S. M.; Harrison, J. R.; Patteson, L.; Valenti, M.; Read, M. A.; Neidle, S.; Kelland, L. R. Mol. Pharmacol. 2002, 61, 1154-1162. (10) Togashi, K.; Kakeya, H.; Morishita, M.; Song, Y. X.; Osada, H. Oncol. Res. 1998, 10, 449-453. (11) Shin-ya, K.; Wiezba, K.; Matsuo, K.; Ohtani, T.; Yamada, Y.; Furihata, K.; Hayakawa, Y.; Seto, H. J. Am. Chem. Soc. 2001, 123, 1262-1263. (12) Sato, A.; Morishita, T.; Shiraki, T.; Yoshioka, S.; Horikoshi, H.; Kuwano, H.; Hanazawa, H.; Hata, T. J. Org. Chem. 1993, 58, 7632- 7634. 10.1021/jo0267910 CCC: $25.00 © 2003 American Chemical Society J. Org. Chem. 2003, 68, 2765-2770 2765 Published on Web 02/26/2003