ChemInform Abstract: The Synthesis of the Labdane Diterpenoid Erigerol and of Analogous Compounds.

Abstract

294ChemInform Abstract The synthesis of the title compound (I) and of some analogues is described in a 23-step sequence starting from (I). The various difficulties of the synthesis and several blind alleys that have been followed are discussed in detail.

Enantiospecific Entry to a Common Decalin Intermediate for the Syntheses of Highly Oxygenated Terpenoids

“…Selective reduction of the C-8 carbonyl of enedione 22 was achieved with sodium borohydride in a dichloromethane–methanol solvent mixture to provide alcohol 23 , which was subsequently protected to yield the desired silyl ether (i.e., 3 ). Spectroscopic data for enantioenriched 3 were fully consistent with the previously reported data. , The synthetic sequence reported here is amenable to the multigram scale preparation of this compound.…”

“…Additionally, cis -decalin 3 can be epimerized to the corresponding trans -decalin ( 24 ) through treatment with basic aluminum oxide, according to Kienzle’s protocol (Scheme ). Thus, all four diastereomers with respect to the decalin ring junctions are accessible through this synthetic route.…”

“…The highly functionalized core in each of these compounds spurred us to identify a common intermediate such as decalin 3 and ent - 3 , which could provide access to each of these compounds. Indeed, racemic 3 has been elaborated to (±)-erigerol ( 4 ) by Kienzle and co-workers and has also been taken forward to (±)-forskolin ( 5 ) in a synthesis by Švenda and co-workers . In light of this previously demonstrated synthetic utility of 3 , we sought to prepare this decalin derivative in enantioenriched form as part of a broad campaign to access a diverse array of enantioenriched terpenoids.…”

“…As noted above, racemic 3 has been prepared previously by Kienzle and co-workers and was utilized in several natural product syntheses . Specifically, from diene 10 and quinone 11 , a Diels–Alder cycloaddition constructed the decalin scaffold (Scheme a).…”

Concise and Practical Total Synthesis of (+)-Abscisic Acid

“…1-Hydroxy-2,6,6-trimethyl-4-oxocyclohex-2-ene-1carbaldehyde (11). 28 To a stirred solution of aldehyde (±)-6 (439 mg, 1.63 mmol) in THF (15 mL) was added 1 M HCl (15 mL). The mixture was stirred at room temperature for 18 h, extracted with EtOAc, dried over anhydrous Na 2 SO 4 , filtered, and concentrated under reduced pressure.…”