Synthesis and antitumor activity of novel per-butyrylated glycosides of podophyllotoxin and its derivatives Cheng-Ting Zi a,b , Dan Yang b , Fa-Wu Dong b , Gen-Tao Li b , Yan Li b , Zhong-Tao Ding a , Jun Zhou b , Zi-Hua Jiang c,⇑ , Jiang-Miao Hu b,⇑ a Key Laboratory of Medicinal Chemistry for Natural Resource, Yunnan University, Kunming 650091, China b State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, China c Department of Chemistry, Lakehead University, 955 Oliver Road, Thunder Bay, ON P7B 5E1, Canada article info Article history: Received 25 November 2014 Revised 31 January 2015 Accepted 11 February 2015 Available online 24 February 2015 Keywords: Podophyllotoxin Epipodophyllotoxin 4 0 -Demethylepipodophyllotoxin Butyrylated glycosides Antitumor Cytotoxic Synthesis abstract A series of perbutyrylated glycosides of podophyllotoxin and its derivatives were synthesized and evaluated for their antitumor activity in vitro. Most of them exhibit cytotoxic activity against a panel of five human cancer cell lines (HL-60, SMMC-7721, A-549, MCF-7, SW480) using MTT assays. Among the synthesized compounds, epipodophyllotoxin a-D-galactopyranoside 8b, epipodophyllotoxin a-D-arabinopyranoside 8e, and podophyllotoxin b-D-glucopyranoside 11a show the highest potency of anticancer activity with their IC 50 values ranging from 0.14 to 1.69 lM. Structure activity relationship analysis indicates that the type of glycosidic linkage, the configuration at C-4 of the podophyllotoxin scaf- fold, and the substitution at 4 0 -position (OH vs OCH 3 ) can all have significant effect on the potency of their anticancer activity. Several compounds are more active than the control drugs Etoposide and Cisplatin, suggesting their potential as anticancer agents for further development. Ó 2015 Elsevier Ltd. All rights reserved. 1. Introduction Podophyllotoxin (1, Fig. 1), extracted from the roots and rhi- zomes of podophyllum species such as Podohyllum hexandrum and Podophyllum peltatum, 1 shows strong cytotoxic activity against various cancer cell lines. Due to its complicated side effects such as nausea, vomiting and damage of normal tissues, attempts to use podophyllotoxin in the treatment of human neoplasia have been mostly unsuccessful. 2 Several podophyllotoxin derivatives such as Etoposide (2, Fig. 1) and Etopophos (3, Fig. 1) have been devel- oped for clinical use as antineoplastic agents. Etoposide and Etopo- phos function as inhibitors of the enzyme DNA-topoisomerase II by stabilizing a cleavable complex in which the DNA is cleaved and covalently linked to the enzyme. 3 Previous structure–activity rela- tionship (SAR) studies have shown that intact A ring, the trans-lac- tone and 4 0 -demethyl moieties are essential to maintain the anticancer activity as topoisomerase II inhibitors. 5–7 More recently, diverse podophyllotoxin analogues have been synthesized in an effort to discover novel anticancer agents with improved therapeu- tic efficacy and to overcome drug resistance. 4,8–11 Preparation of glycoconjugates of small molecule anticancer drugs has become an attractive strategy in recent years in order to improve drug efficacy and pharmacokinetics, and reduce side effects. 12–14 Both Etoposide (2) and Etopophos (3), the two anti- cancer drugs widely prescribed in the clinic, are derivatives of b-D-glucopyranoside of 4 0 -demethylepipodophyllotoxin. Besides b-D-glucopyranosides, other types of podophyllotoxin glycosides are quite limited. 15–20 For example, a-D-glucoside, a-D-galactoside, and D-mannoside are still not known for podophyllotoxin and its derivatives. Thus, in the present study we plan to synthesize a ser- ies of glycoconjugates of podophyllotoxin, epipodophyllotoxin, and 4 0 -demethylepipodophyllotoxin combined with a number of differ- ent sugars. Short chain fatty acid (SCFA)-derivatized 2-deoxy-2-acetamido- D-mannose (ManNAc) analogs such as O-butyrylated ones were originally designed to increase the lipophilicity and cellular uptake of ManNAc in modifying cell surface carbohydrates in living cells. Some of the butyrylated ManNAc analogs also showed consider- able anti-cancer effects including the induction of apoptosis, inhi- bition of NF-jB, and suppression of proinvasive oncogenes. 21–23 Earlier studies suggested that the anticancer activity of these butyrylated ManNAc analogs may be partly contributed by the http://dx.doi.org/10.1016/j.bmc.2015.02.021 0968-0896/Ó 2015 Elsevier Ltd. All rights reserved. ⇑ Corresponding authors. Tel.: +1 807 766 7171; fax: +1 807 346 7775 (Z.-H.J.); tel.: +86 871 6522 3264; fax: +86 871 6522 3261 (J.-M.H.). E-mail addresses: zjiang@lakeheadu.ca (Z.-H. Jiang), hujiangmiao@mail.kib.ac.cn (J.-M. Hu). Bioorganic & Medicinal Chemistry 23 (2015) 1437–1446 Contents lists available at ScienceDirect Bioorganic & Medicinal Chemistry journal homepage: www.elsevier.com/locate/bmc