Pettit, George R. Mendonça, Ricardo F. Knight, John C. Pettit, Robin K. The Cephalostatins. 21. Synthesis of Bis-steroidal Pyrazine Rhamnosides The synthesis of bis-steroidal pyrazines derived from 3-oxo-11,21-dihydroxypregna-4,17(20)-diene (<b>4</b>) and glycosylation of a D-ring side chain with α-l-rhamnose have been summarized. Rearrangement of steroidal pyrazine <b>10</b> to <b>14</b> was found to occur with boron triflouride etherate. Glycosylation of pyrazine <b>10</b> using 2,3,4-tri-<i>O</i>-acetyl-α-l-rhamnose iodide led to 1,2-orthoester-α-l-rhamnose pyrazine <b>17b</b>. By use of a persilylated α-l-rhamnose iodide as donor, formation of the orthoester was avoided. Bis-steroidal pyrazine <b>10</b> and rhamnosides <b>17b</b> and <b>21c</b> were found to significantly inhibit cancer cell growth in a murine and human cancer cell line panel. Pyrazine <b>9</b> inhibited growth of the nosocomial pathogen <i>Enterococcus faecalis</i>. 21 c;nosocomial pathogen Enterococcus faecalis;steroidal pyrazine 10;rhamnosides 17 b;Pyrazine 9;cancer cell growth;21. Synthesis;iodide;cancer cell line panel;boron triflouride etherate;orthoester;pyrazine 10 2011-09-23
    https://acs.figshare.com/articles/journal_contribution/The_Cephalostatins_21_Synthesis_of_Bis_steroidal_Pyrazine_Rhamnosides/2611681
10.1021/np200411p.s001