OXIDATION OF FUROST-20(22)-ENES WITH 3-CHLOROPEROXYBENZOIC ACID AND OSMIUM TETROXIDE Jacek W. MORZYCKI 1, *, Izabella JASTRZĘBSKA 2 and Krzysztof S. KATRYŃSKI 3 Institute of Chemistry, University of Bialystok, al. Pilsudskiego 11/4, 15-443 Bialystok, Poland; e-mail: 1 morzycki@uwb.edu.pl, 2 gierdas@uwb.edu.pl, 3 katryn@wp.pl Received July 11, 2001 Accepted November 18, 2001 Dedicated to the memory of Professor Václav Černý. 6 β-Methoxy-3 α,5-cyclo-5 α-furost-20(22)-ene and its 17 α-hydroxy derivative were oxidized with 3-chloroperoxybenzoic acid and OsO 4 . The former compound afforded hydroxylated products, whereas the latter underwent degradation to C 21 or C 19 steroids. Ke y w o rd s : Pseudosapogenins; Furostanes; Oxidations; Steroids; Steroidal saponins. Steroidal saponins comprise a diverse class of plant glycosides which pos- sess a broad range of interesting biological activities 1,2 . The most common are saponins with the steroid aglycone (sapogenin), such as spirostane or furostane derivatives 3 . A number of polyhydroxy cholestane saponins with cytostatic activity was recently reported 4–7 . When treated with carboxylic acid anhydrides, steroid sapogenins undergo cleavage of ring F (refs 8,9 ). The products are furost-20-enes called pseudo- sapogenins. These compounds are intermediates in the transformation of spirostanes to medicinally useful pregnane derivatives. Oxidation of pseudo- sapogenins with various reagents, such as CrO 3 /AcOH, KMnO 4 /NaIO 4 or H 2 O 2 /AcOH, has been intensively studied 10,11 . These reactions led to cleav- age of ring E. Interestingly, a similar process also takes place in nature and the corresponding saponins were recently found in some Chinese medici- nal plants 12 . It is postulated that 20,22-epoxide is an intermediate in this enzymatic oxidation. In the chemical oxidation of pseudosapogenins vari- ous compounds, such as diols, epoxides or allylic alcohols, were proposed as intermediates 3 . However, the final reaction products were 16 β-hydroxy- pregnan-20-one esters or pregn-16-en-20-one derivatives. In the oxidation of pseudosapogenins containing a free 26-hydroxy group with 3-chloro- peroxybenzoic acid (MCPBA), the products were 20-hydroxyspirostanes 13 . Collect. Czech. Chem. Commun. (Vol. 66) (2001) 1746 Morzycki, Jastrzębska, Katryński: doi:10.1135/cccc20011746