Steroids 76 (2011) 232–237 Contents lists available at ScienceDirect Steroids journal homepage: www.elsevier.com/locate/steroids Synthesis of new symmetrical bis-steroidal pyrazine analogues from diosgenin Khaled Q. Shawakfeh ∗ , Naim H. Al-Said Department of Applied Chemical Sciences, Jordan University of Science and Technology, P.O. Box 3030, Irbid 22110, Jordan article info Article history: Received 23 August 2010 Received in revised form 4 October 2010 Accepted 6 October 2010 Available online 15 October 2010 Dedicated to Prof. John R. Williams for his continuos support. Keywords: Steroidal Pyrazine Diosgenin Dimers Oxysterol abstract New symmetrical bis-steroidal pyrazine dimers that are cephalostatins/ritterazines analogues have been prepared easily from a cheap, readily available natural steroid (diosgenin). These dimers were obtained by classical, condensation of -amino ketones in order to construct the pyrazine rings. The three dimers differ in the functionalized diosgenin: (25R)-5,6-dihydroxy-5-spirosta-3-one, (25R)-4,5-epoxy- 5-spirosta-3,6-dione and (25R)-5-hydroxy-5-spirosta-3,6-dione respectively. © 2010 Elsevier Inc. All rights reserved. 1. Introduction Marine species such as sponges, coelenterates, mollusks and echinoderms are a rich source of a large variety of polyhydroxy steroids [1]. The synthesis of polyhydroxy sterols has been a chal- lenging subject for several years. Diosgenin is the steroidal saponin that is isolated from the Mexican yam. Due to its structural simi- larity to estrogen and progesterone precursors, diosgenin exhibts estrogenic, progesterogenic and anti-inflammatory effects [2]. In addition, diosgenin was used for the synthesis of nearly 50% of the total steroid drugs in the world [2]. In 1988, a family of dimeric steroid-pyrazine alkaloids and dimers was discovered by the Pettit group [3]. Latter, as a continuation of their work on these dimers, during the period from 1988 to 1998, the same group reported the isolation and identification of compounds of this class, cephalo- statines 2-19 [4–6]. For example Cephalostatin 1 (Fig. 1) was proved to be one of the most powerful cancer cell growth inhibitors with an ED 50 value of 0.1–0.001 pM. This exceptional activity of cephalo- statins has led to interest in the synthesis of compounds and their analogues as potential anti-tumor agents [7]. The cephalostatin 1 and the closely related ritterazines B share many common structural features in which two highly oxygenated C 27 steroidal units are fused via a pyrazine ring at C-2 and C-3 and both chains of the steroidal units form spiroketals [8]. The cephalostatins in general are more oxygenated on the right side, ∗ Corresponding author. Tel.: +962 2 7201000; fax: +962 2 7095014. E-mail address: shawakfa@just.edu.jo (K.Q. Shawakfeh). whereas the ritterazines have the more oxygenated left side. These natural steroid dimers possess extremely potent inhibitory activ- ity against a series of human cancer cell lines and the murine P388 lymphocytic leukemia cell line [7b,9]. Since the natural sources of these compounds are extremely limited, and also the yield of these compounds in nature is rather poor, the syntheses of a number of various analogues of cephalostatines and ritterazines have been reported in the literature [10–12]. There are many synthetic approaches for the central pyrazine ring. Some of them describe the synthesis of unsymmetrical dimers [13]. The symmetrical dimeric steroid-pyrazines can be obtained by the classical condensation of -amino ketones. This route is actu- ally, the most efficient method of pyrazine rings construction. The intermediate steroidal 2-amino-3-ketones are available by reduc- tion of the corresponding 3-ketones with a nitrogen containing substituent at C-2, such as azido [14] nitro [15], hydroxyimino [16] and enamino [17] groups. The initially formed 2-amino-3-ketones undergo spontaneous dimerization to a mixture of dihydropy- razines, which are then oxidized by air to give pyrazine dimers [3]. A new methodology for the synthesis for four new cephalostatin analogues was reported by Shawakfeh et al. [18]. The main com- ponent of the steroid mixture was the known diosgenin, which has a spiroketal ring in the side chain. As a continuation of our studies and due to the structural similarities between cephalo- statin/rittarazine and diosgenin, we report here the synthesis of three new polyoxgenated symmetrical bis-steroidal pyrazine ana- logues that are expected to show more biological effect due to the increased presence of polar functional groups. 0039-128X/$ – see front matter © 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.steroids.2010.10.002