1: nBu4NF*3H2O / tetrahydrofuran / 23 h 2: 20 mg / AG 50W-X4 resin / methanol / 24 h View Scheme

<b>Multi-step reaction with 3 steps<br /> </b>1.1: 89 percent / aq. H₂SO₄ / acetone / 2.5 h / ultrasonication<br />2.1: 99 percent / PDC / CH₂Cl₂ / 6 h<br />3.1: nBuLi / hexane; tetrahydrofuran / 5 h / -78 - 0 &deg;C<br />3.2: 73 percent / tetrahydrofuran; hexane / 5 h / 20 &deg;C<br /> <br /> &nbsp;

Stage #1: <a href="#" onclick="return RXDsubstances(event, this, '4556676', constants.ctx, '0')">lt;lt;(1Z),(5S)gt;-2-lt;5-(t-butyldimethylsilyl)oxy-2-methylcyclohexylidenegt;gt;diphenylphosphine oxide</a> <b>With</b>&nbsp; <a href="#" onclick="return RXDsubstances(event, this, '1209227', constants.ctx, '0')">n-butyllithium</a>&nbsp;<b>in</b>&nbsp; <a href="#" onclick="return RXDsubstances(event, this, '102391', constants.ctx, '0')">tetrahydrofuran</a>;&nbsp;<a href="#" onclick="return RXDsubstances(event, this, '1730733', constants.ctx, '0')">hexane</a> <br />T=-78 - 0&deg;C;&nbsp;Wittig-Horner reaction;&nbsp;5&nbsp;h;&nbsp;<br />Stage #2: <a href="#" onclick="return RXDsubstances(event, this, '9221070', constants.ctx, '0')">(24R)-de-A,B-24,25-dihydroxycholestan-8-one cyclic 24,25-(1-methylethylidene acetal)</a> &nbsp;<b>in</b>&nbsp; <a href="#" onclick="return RXDsubstances(event, this, '102391', constants.ctx, '0')">tetrahydrofuran</a>;&nbsp;<a href="#" onclick="return RXDsubstances(event, this, '1730733', constants.ctx, '0')">hexane</a> <br />T=20&deg;C;&nbsp;Wittig-Horner reaction;&nbsp;5&nbsp;h;&nbsp;&nbsp;Further stages.;&nbsp;<br /> &nbsp;