An Unexpected (3→2)-Hydride Shift in Phyllocladane (=13β-Kaurane) Diterpenoids and in Related Trimethyl-Substituted Bi- and Tricyclic Compounds
✍ Scribed by Ralph Müller; Peter Rüedi
- Book ID
- 102253553
- Publisher
- John Wiley and Sons
- Year
- 2003
- Tongue
- German
- Weight
- 331 KB
- Volume
- 86
- Category
- Article
- ISSN
- 0018-019X
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✦ Synopsis
Abstract
The conversion of 2__α__,3__α__‐dioxy‐substituted phyllocladane derivatives into the corresponding 3‐ketone proceeds in an unexpected manner: Depending on the reaction conditions, the corresponding 3__β__‐hydroxy‐substituted compound is formed almost quantitatively, or the desired ketone can be isolated directly (see preceding paper). The reaction mechanism is now disclosed to be a stereospecific C(3)→C(2)‐hydride shift by investigating the reactions of the synthesized (±)‐trans‐decalin‐type (trans‐1,5,5‐trimethylbicyclo[4.4.0]decanes) and (±)‐podocarpane‐type (trans‐1,2,3,4,4a,9,10,10a‐octahydro‐1,1,4a‐trimethylphenanthrenes) model compounds 25 and 35 and of their D‐labeled isomers 25′ and 35′ (Scheme 6). The latter afforded the corresponding 3__β__‐hydroxy (2__β__‐D)‐derivatives 38 and 39 as well as the (2__β__‐D)‐3‐ketones of the general type 5b′ (e.g., 36′), thus evidencing a suprafacial (C3)→C(2)‐deuteride shift. This reaction mechanism seems to be a general feature of such 3__α__,4__α__‐dioxy‐substituted 1,5,5‐trimethylbicyclo[4.4.0]decane congeners.