Stereocontrolled Construction of the Tricyclic Framework of Tiglianes and Daphnanes by an Oxidative Dearomatization Approach

Abstract

An appropriately functionalized [5-7-6] tricyclic framework of tigliane and daphnane diterpenes containing seven contiguous stereocenters has been prepared in 10 steps from very simple building blocks in a modular and stereocontrolled fashion. The key features of this approach involve an efficient visible light-induced singlet oxygen oxidative dearomatization and an array of substrate-controlled highly diastereoselective transformations. This work provides a model strategy for rapid and diverted synthesis of natural and unnatural molecules sharing the common skeleton.

A Divergent Approach to the Marine Diterpenoids (+)‐Dictyoxetane and (+)‐Dolabellane V

“…In this approach, (+)‐dictyoxetane ( 3 ) was traced back to enone 10 ; the latter could be obtained through elaboration of the key intermediate, dioxatricycle 11 . We envisaged an intramolecular oxidative dearomatization of phenol 12 as a novel method to forge the oxetane of 11 …”

“…In this approach, (+ +)-dictyoxetane (3)w as traced back to enone 10;t he latter could be obtained through elaboration of the key intermediate, dioxatricycle 11.W ee nvisaged an intramolecular oxidative dearomatization of phenol 12 as an ovel method to forge the oxetane of 11. [23] Finally,w ew ere also interested in pursuing as ynthetic approach,w hich is inspired by Hoffmann'sb iosynthetic proposal. [14] Based on this, (+ +)-dolabellane V( 6)i st he biogenetic precursor of (+ +)-dictyoxetane (3)b ym eans of at ransannular cyclization to forge the 5-6-7 ring system 14.Stereoselective epoxidation of the C13/C14 olefin in the latter compound, followed by 3-exo-tet cyclization would then give epoxide 15 as the key biosynthetic intermediate.…”

Z‐bpy, a New C2‐Symmetric Bipyridine Ligand and Its Application in Enantioselective Copper(I)‐Catalyzed Cyclopropanation of Olefins

“…Cyclopropane substructures are frequently seen in natural products, drugs, pesticides and other functional molecules. [8] Also, the high strain and unique bonding of cyclopropanes make them competent intermediates in synthesis of other molecules via ring opening or expansion. [9] Therefore, the development of highly efficient chiral catalysts, such as Cu-, Rh-, Ru-, and Co-based complexes, resulted in important advances in cyclopropane chemistry, providing access to the smallest ring compounds with a wide variety of functional groups, including ethers, amines, phosphonates, and carbonyl groups.…”

Total Synthesis of (±)-Prostratin

“…As shown in the retrosynthetic analysis of prostratin (1) (Figure 2), whereas the B ring should be formed by ring-closing olefin metathesis reaction from diene 6, the A-ring and C-ring skeletons were to be introduced directly from diol 10 and Grignard reagent 11 at the early stage. 60 Diol 10 was known to be readily available in either racemic or enantiopure form in three or four steps from simple commercially available chemicals. [61][62][63] The densely functionalized C ring, arguably the most challenging part, would be established from the phenol moiety in 9 by a regio-and stereocontrolled functionalization sequence including oxidative dearomatization (9 to 8), hydroxyl group-guided sequential 1,4-additions, 2-propenyl cross-coupling (8 to 7), and cyclopropanation (7 to 6).…”