Expedient access to enantiopure cyclopentanic natural products: total synthesis of (-)-cyclonerodiol.

Following the principles of collective total synthesis, a number of natural products sharing an optically pure, multifunctional, cyclopentanic core were synthesized from a common precursor: plinol A (1). This intermediate was efficiently obtained in only four steps from (-)-linalool (2) using as the key step a Ti(III)-mediated diastereoselective radical cyclization. The feasibility of this approach was confirmed with the expedient enantiospecific synthesis of cyclonerodiol (3), and the formal synthesis of chocol G (4) and piperitone (5).

Structural diversity from the transannular cyclizations of natural germacrone and epoxy derivatives: a theoretical-experimental study.

Treatment of germacrone (1) with different electrophiles, and of its epoxy derivatives germacrone-4,5-epoxide (2), germacrone-1,10-epoxide (3) and isogermacrone-4,5-epoxide (4) with Brönsted/Lewis acids and Ti(III), gives rise to a great structural diversity. Thus, by using a maximum of two steps, the production of more than 40 compounds corresponding to 14 skeletons is described. Computational calculations rationalizing the structural divergence produced are also described.

Protecting-group-free synthesis of chokols.

As a result of a combined theoretical and experimental study, we describe a two-step protocol for the preparation of an optically pure, multifunctional, cyclopentanic core shared by a number of natural products. This process is based on a hitherto unreported Ti(III)-mediated diastereoselective cyclization in which the hydroxy-directed template effect played by the Ti(III) species was found to be crucial for the stereoselective outcome of the reaction. The viability of this concept was confirmed with the first protecting-group free synthesis of three enantiopure chokols, namely, chokols K, E, and B.

Efficient synthesis of the anticancer β-elemene and other bioactive elemanes from sustainable germacrone.

Highly efficient preparations of anticancer β-elemene and other bioactive elemanes were carried out using the natural product germacrone as a renewable starting material. The syntheses were achieved in only 3-5 steps with excellent overall yields (43-54%). An enantioselective approach to these molecules is also described.