Bioinspired synthesis of pentacyclic onocerane triterpenoids

Abstract

The first chemical synthesis of pentacyclic onocerane triterpenoids (+)-cupacinoxepin and (+)-onoceranoxide is described.

Synthesis of (+)-Vitepyrroloid A and (+)-Vitepyrroloid B by Late-Stage Ni-Catalyzed C(sp2)–C(sp3) Cross-Electrophile Coupling

“…The pyrrole coupling partner 4 is accessible from the commercially available pyrrole derivative 6 . For the synthesis of the decalin coupling partner 5 , we identified the terpenoid (+)-sclareolide as potential starting material − in accordance with long-standing interest in the utilization of terpene feedstock as suitable building blocks, − thus minimizing the number of C–C bond-forming reactions.…”

“…Methyl 2-((1aR,7aS,7bS)-1a,4,4,7a-Tetramethyloctahydronaphtho [1,2-b]oxiren-7b(1aH)-yl)acetate (12). TFAA (0.21 mL, 1.51 mmol, 2.0 equiv) was added dropwise to a suspension of UHP (156 mg, 1.66 mmol, 2.2 equiv) in MeCN (4.6 mL) at 0 °C.…”

Indium(III)-Catalyzed Stereoselective Synthesis of Tricyclic Frameworks by Cascade Cycloisomerization Reactions of Aryl 1,5-Enynes

“…As an example, cascade polyene cyclizations are one of the most impressive biosynthetic transformations known, and their chemical emulation represents a major challenge in modern synthetic chemistry . Usually, these transformations involve the epoxide activation in a polyenic compound using oxophilic Lewis acids under stoichiometric or catalytic conditions . Alternatively, electrophilic alkyne activation under metal catalysis has been recently envisaged as a different synthetic approach to promote catalytic cascade polyenynic π-cyclizations .…”

Synthesis of Spongidine A and D and Petrosaspongiolide L Methyl Ester Using Pyridine C–H Functionalization

“…Reduction of (+)-sclareolide with LiAlH 4 and in-situ benzylation was followed by a Wittig-type fragmentation of the intermediate 2-methyl benzyl ether (not shown) to give alkene 3 in multigram quantities. 11 Iodide 4 was prepared from pyridine 5 on gram scale in 91% yield using a Sandmeyer reaction. 12,13 The coupling of 3 and 4 required intensive optimization.…”

“…These coupling partners are readily accessible from (+)-sclareolide (8) The synthesis commenced with the preparation of alkene 6 from (+)-sclareolide using our previously established two-step procedure (Scheme 2). 11 Reduction of (+)-sclareolide (8) with LiAlH 4 and in situ benzylation was followed by a Wittig-type fragmentation 12 of the intermediate 2-methyl benzyl ether (not shown) to give alkene 6 in multigram quantities. Iodide 7 was prepared from pyridine 9 on gram scale in 91% yield using a Sandmeyer reaction.…”