Base-Induced and -Directed Elimination and Rearrangement of Perhydronaphthalene-1,4-diol Monosulfonate Esters. Total Synthesis of (+/-)-Alloaromadendrane-4β,10α-diol and (+/-)-Alloaromadendrane-4α,10α-diol

Article abstract of DOI:10.1021/jo00023a025

The total synthesis of (+/-)-alloaromadendrane-4β,10α-diol (1), supposedly isolated from Ambrosia peruviana Willd., is described.The strategically positioned axial hydroxyl group at C(4) played a crucial role in the two key steps of this synthesis (2 and 11 -> 3; 4 -> 5).Upon treatment with sodium tert-amylate in refluxing toluene, both the mesylates 2 and 11 predominantly gave the olefin 3.A mechanism for this regioselective elimination is proposed.The double bond of 3 at C(6)-C(7) was used to introduce a dimethylcyclopropane ring at this position.The intramolecular base-induced rearrangement of 4 proceeded with high selectivity, again guided by the alkoxide at C(4).The resulting exo olefin 5 was converted into diol 1, but its spectral data did not agree with those reported for the natural diol.The epimeric (+/-)-alloaromadendrane-4α,10α-diol (23) was prepared from 5 via a dehydratation, epoxidation, reduction sequence.Now the spectral data of the natural and the synthetic diol agreed very well and a revision of the structure of the natural product is postulated.