136379-64-1Relevant academic research and scientific papers
Synthesis of (E,E)-Germacrane Sesquiterpene Alcohols via Enolate-Assisted 1,4-Fragmentation
Minnaard, Adriaan J.,Wijnberg, Joannes B.P.A.,De Groot, Aede
, p. 7336 - 7345 (2007/10/03)
An efficient method has been developed for the synthesis of (E,E)-germacrane sesquiterpene alcohols. The key step in these syntheses involves the enolate-assisted 1,4-fragmentation of properly functionalized perhydro-1-naphthalenecarboxaldehydes with 1 equiv of sodium tert-amylate as base, to give the corresponding (E,E)-germacrane aldehydes. These aldehydes are not very stable, and in situ reduction of the aldehyde function with Red-Al is required to obtain high yields of the desired germacrane alcohols. This procedure has led to the successful synthesis of 15-hydroxygermacrene B (4) and 15-hydroxyhedycaryol (35) from the mesylates 6 and 33, respectively. When KHMDS is used instead of sodium tert-amylate in the fragmentation reaction of 6, isomerization of the initially formed C(4)-C(5) E double bond cannot be avoided and results, after in situ reduction with Red-Al, in the formation of the (E,Z)-germacrane alcohol 24. The 15-hydroxy-(E,E)-germacranes are excellent starting materials for the selective synthesis of the corresponding 4,5-epoxides, which in turn can perfectly well be used in studies on the biomimetic formation of guaiane sesquiterpenes.
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
Jenniskens, Louis H. D.,Wijnberg, Joannes B. P. A.,Groot, Aede de
, p. 6585 - 6591 (2007/10/02)
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.
