Asymmetric Total Synthesis of (+)-Neooxazolomycin Using a Chirality-Transfer Strategy.

The total synthesis of (+)-neooxazolomycin was achieved from the amino-acid d-serine. The efficiency of this approach is derived from the use of principles of memory of chirality and dynamic kinetic resolution in the intramolecular aldol reaction of a serine derivative to build the densely functionalized lactam framework and to install three contiguous stereocenters. The key intermediate was readily elaborated to the target natural product.

Calix[n]triazoles and Related Conformational Studies.

Calix[n]triazoles are developed as new derivatives in the calixarene family. Calixtriazole compounds 2-4 are synthesized using an iterative convergent strategy including an inter-/intramolecular copper(I)-catalyzed azide-alkyne cycloaddition reaction. Solid-state structures are clearly refined to give 1,2-alternate and partial cone conformations for calix[4]triazole and calix[5]triazole, respectively. Theoretical studies based on density functional theory (DFT) calculations indicated that intermolecular interactions are crucial in determining the conformers of the crystals, and the most stable conformers of calix[4]triazole, calix[5]triazole, and calix[6]triazole in the monomeric forms are 1,3-alternate, 1,3-alternate, and 1,3,5-alternate, respectively.

Platinum-catalyzed synthesis of substituted phenanthrenes from biphenyl propargyl alcohols via a carbene intermediate.

An efficient synthesis for phenanthrenes via a Pt-carbene intermediate is described. Using Pt as a catalyst, the readily accessible biphenyl propargyl alcohol substrate can be transformed to the vinylphenanthrene system through a cascade involving electrophilic cyclization, dehydration, and 1,2-H migration. The synthetic utility and efficiency of this protocol were demonstrated via the concise total synthesis of antofine.