Enantioselective Synthesis of Iridal, the Parent Molecule of the Iridal Triterpenoid Class

Abstract

The monocyclic triterpene iridal 1 (parent molecule) is synthesized by an approach that allows access for several representatives of the iridal family as well as diversely substituted analogues. The success of the proposed synthetic plan depends upon the effortless stereoselective establishment of the trans C10/C11 dimethyl relationship in B-ring moiety 7 using a domino-based methodology and the higly efficient Miyaura-Suzuki type sp3-sp2 segment coupling 7 and 8, respectively.

Current Status and Future Prospects of C1 Domain Ligands as Drug Candidates

“…Furthermore, these compounds showed anti-tumor activity in several cell lines including A2780 and K562 human tumor cell lines as well as in the NCI (US) 60-cancer cell line screen. Recently, the first total synthesis of an iridal (75, R1 = Me, R2 = homofarnesyl) was performed, requiring over 20 steps [239].…”

Microwave-assisted domino reactions: function-compatibility, modulation, and greening efforts

“…The process accommodates free b-hydroxyl groups (entry 2), while it tolerates a wide range of protecting groups. Domino reactions with substrates bearing alkenes (entries 3,6,[8][9][10], oxygen-heterocycles (entry 5), ketones (entry 7), and ketals (entries 6 and 7) proceed efficiently to afford the corresponding ring-expanded domino products under either set of conditions (microwave heating, room temperature stirring). The lowest yields were obtained with the diols 1h and 1i in the angularly substituted series.…”

“…However, under microwave heating, even at 100°C, no such complications were observed. For example, microwave irradiation of 1i, 10, 11, 13, and 14 resulted in the formation of 2j, 23-26 with domino yields in the range of 60-84% (entries 6,[8][9][10], devoid of any side product. In all cases investigated, microwave heating was found to be more desirable compared to both conventional heating (20- (over 100-fold increase in rate).…”

“…3 The starting hydrindene-diols of type-1 can be readily assembled and constitute attractive precursors for highly elaborated type-3 or 6 cyclohexanes, type-4 bridged bicyclic systems, and type-5 fused -bicyclic lactones. 4 Since our early observations, the oxidative cleavage of unsaturated bicyclic diols has been of extensive value in the synthesis of taxol's C-ring, 5 iridal's B-ring, 6 norsesquiterpene spirolactone's B-ring, and their steroid hybrids. 7 The fact that a harsh reagent such as Pb(OAc) 4 8 required to induce the domino reaction means that the scope of the method is limited to substrates that lack sensitive functionality.…”

Natural and Unnatural A‐seco Terpenes from Pulegone: Synthesis of Galbanic Acid and Marneral Revisited

“…Through the success achieved in improving the marneral [(+)-7] synthesis, the stage was set to test the planned bioconversion to the iridal parent molecule (+)-25 and several representatives of the iridal family (Scheme 7) with the ultimate goal to shorten our domino-based route [25] by more than 10 linear steps before coupling. The characterization of cytochrome P450 in Iris rhizomes [26] and the known reactivity of this monooxygenase towards the iridal parent molecule leading to 16-hydroxy-iridal, [27] along with the recently reported bioinspired rigid iron catalyst [Fe(pdp)], [28] Scheme 7.…”