A concise total synthesis of the antiproliferative macrolide (+)-neopeltolide has been completed, utilising a Jacobsen hetero Diels-Alder reaction to install the trisubstituted tetrahydropyran ring.

A new approach to the medicinally-important natural product triptolide is significantly shorter than previous syntheses, highly convergent and avoids the use of protecting groups; key features include two Diels-Alder reactions and a new deoxygenative aromatisation process.

On a short fuse: Highly stereoselective and atom‐efficient domino Diels–Alder/lactonization/Diels–Alder sequences can be carried out using simple chiral [3]dendralenes to form fused‐ring systems. This short and general approach to cross‐conjugated systems promotes the rapid assembly of enantiomerically pure polycyclic ring systems common to biologically interesting terpenoids with virtually complete stereocontrol (see scheme).

No abstract

The stereochemical outcome of the intramolecular Diels-Alder reaction of ester-linked 1,3,8-nonatrienes can be controlled by substituents about a stereogenic center attached to C1. The scope and limitations of this approach have been investigated, with variation in substrate structure about the allylic stereocenter and the dienophile. The stereochemical outcomes of these reactions are explained by reference to B3 LYP/6-31G(d) transition structures. New insights into the conformational preferences of allylic alcohol derivatives are reported, results which allow an explanation of the differing levels of pi-diastereofacial selectivity and cis/trans (i.e. endo/exo) selectivity from the reaction.