Facile reductive oxy-Nazarov cyclization of 2-methoxy-2, 4-hexadienoates

Bioinspired Total Synthesis of 3-epi-Junipercedrol

A bioinspired total synthesis of 3-epi-junipercedrol, which contains a strained tricyclo[5.2.2.03,7]undecane allo-cedrane framework and five stereocenters, was accomplished via an effective anionic semipinacol rearrangement of a tricyclic cedrane mesylate. The corresponding cedrane precursor was synthesized efficiently by employing the reductive oxy-Nazarov cyclization and an intramolecular aldol condensation as the key steps. This synthetic approach provided a further evidence for the biogenetic relationship between the typical cedrane and allo-cedrane sesquiterpenoids.

Reductive Oxy-Nazarov Cyclization toward Expedient Construction of a Cyclopenta[1,2-b]pyrrolo[1,2-a]azepine Ring System: Formal Total Syntheses of Stemonamine and Cephalotaxine

Formal total syntheses of stemonamine and cephalotaxine bearing the core cyclopenta[1,2-b]pyrrolo[1,2-a]azepine ring skeleton were achieved. The general synthetic strategy in the synthesis features the reductive oxy-Nazarov cyclization as key step, leading to the versatile construction of N-substituted spiro quaternary stereogenic centers from readily available starting materials.

The iso-Nazarov reaction

The acid-promoted cycloisomerization of conjugated dienals and linearly-conjugated dienones for the synthesis of five-membered ring systems is reviewed.