Chiral Economy with Respect to Rotational Isomerism: Rational Synthesis of Hamatine and (Optionally) Ancistrocladine from Joint Helical Precursors

Atroposelective Total Synthesis of the Fourfold ortho‐Substituted Naphthyltetrahydroisoquinoline Biaryl O,N‐Dimethylhamatine

“…The high atropo‐diastereoselectivity of the biaryl coupling achieved by the method described here, to give an M ‐axial configuration as in hamatine ( 1 ), is remarkable and opposite to the outcome of our previous synthesis of korupensame B involving a Suzuki–Miyaura biaryl coupling . Although in that case, the M ‐isomer was also obtained, it was starting from an R ‐configuration at C‐3, whereas here, M was yielded starting from a 3 S ‐configured precursor, i.e., selectively leading to the opposite relative axial configuration.…”

“…This bifurcation raised the question of whether the stereoselectivity observed for M ‐ 28 and P ‐ 28 could arise from dynamical factors on the way downhill from the reductive elimination transition states if it were possible for both diastereomers to be formed after transition states TSC or TSD . This was tested by looking at trajectories from ADMP calculations for transition states TSK and TSL leading to their diastereomeric products on bifurcation surfaces. In neither case did trajectories show any crossover from a transition state more resembling one diastereomer to lead to the opposite diastereomer, indicating that the diastereoselectivity of the reactions is determined by the transition state energies, not by dynamical factors afterwards on the surface.…”

The Lactone Concept: An Efficient Pathway to Axially Chiral Natural Products and Useful Reagents

“…Moreover, the undesired minor atropo-diastereomer (e.g. 0-E) is not lost, it can be easily recycled (Scheme 5), literally just by chemical cyclization back to the lactone, here to E, and renewed ring cleavage -chiral economy in the field of atropisomerism, 43 48 In each of these cases, the undesired atropoenantiomer is no longer detectable after a single crystallization step.…”

β-Phenylethylamines and the isoquinoline alkaloids

“…coclaurine, N-methylcoclaurine, and reticuline Thalictrum pedunculat~m~~ reticuline The structures of the new alkaloids were deduced from spectroscopic data and that of phyllocryptonine was confirmed by synthesis from (22) (obtained by Bischler-Napieralsky synthesis) by oxidation to (23), followed by reduction, debenzylation, and quaternization ; 26 and velucryptine was obtained by oxidation of the corresponding benzyldihydro-isoq~inoline.~~ The fast atom bombardment mass spectra of…”