Studies for a Diastereoselective Synthesis of the Tetracyclic Diterpenic Diol Stemarin: A Model Study for a New Preparation of the Key Intermediate and the Synthesis of (+)-18-Deoxystemarin
Methods for a stereoselective preparation of compounds of type 2b, a keyintermediate of a previous synthesis of the tetracyclic diterpene stemarin (la), have been tested on model compounds 5a, 5c, and 8a. Thus, (±)-(1RS,6SR,8SR,11SR)-hydroxytricyclo[6.2.2.0l,6]dodecan-9-one (5a) was transformed by the Mitsunobu reaction into (±)-(1RS,6SR,8SR,11RS)-11-(benzoyloxy)tricyclot[6.2.2.01,6]dodecan-9-one
Elusive 6-<i>e</i><i>xo</i>-Hydroxybicyclo[2.2.2]octan-2-ones from the Corresponding Acetates by Methanolysis in the Presence of CH<sub>3</sub>ONa/La(OTf)<sub>3</sub>
作者:Stefano Di Stefano、Francesca Leonelli、Barbara Garofalo、Luigi Mandolini、Rinaldo Marini Bettolo、Luisa Maria Migneco
DOI:10.1021/ol026326p
日期:2002.8.1
text] A series of 6-exo-acetoxybicyclo[2.2.2]octan-2-ones were converted into the corresponding 6-exo-hydroxybicyclo[2.2.2]octan-2-ones by methanolysis in the presence of CH(3)ONa/La(OTf)(3). Under the given conditions, epimerization at C(6) of the latter led in the least favorable cases only to traces of the more stable 6-endo-hydroxybicyclo[2.2.2]octan-2-ones. This procedure, when combined with the