Stereospecific total synthesis of gibberellic acid. A key tricyclic intermediate

Highly Efficient and Selective Deprotection Method for Prenyl, Geranyl, and Phytyl Ethers and Esters Using Borontrifluoride–Etherate

“…Our literature survey revealed that several alkyl groups (methyl, [7][8][9][10] ethyl, [11] t-butyl [12,13] ) have been used to protect the phenolic compounds; however, they need drastic conditions for protection as well as deprotection, which also affect other functional groups. Newer protecting groups such as methoxymethylchloride (MOMCl) [14][15][16][17][18] methoxyethoxymethylchloride (MEMCl), [19] 2-(trimethylsilyl) ethoxymethylchoride (SEMCl), [20,21] and tetrahydrophyranoether (THP ethers) [22,23] have been developed that needs milder conditions. The prenyl group has also been used for protection of alcohols and phenols; [24][25][26][27][28][29][30][31][32][33][34] however, the reported reagents in deprotection of the prenyl group lack selectivity in multifunctional compounds.…”

Racemic synthesis of 1,2-secomicrominutinin

“…Attempts to use other bases (NaH, KOH, t-BuOK) instead of TBAF favors the protection of both hydroxyl groups. The protection of the second hydroxyl group 9 by reaction of 9 with methoxymethyl chloride and N,N-diisopropylethylamine (DIPEA) 10 furnished compound 10 in 95% yield. The reduction of the carboxyl group 11 of compound 10 with LiAlH 4 furnished the corresponding alcohol 11 in 96% yield.…”

“…Methyl 2-(benzyloxy)-6-hydroxybenzoate (9). A solution of methyl 2,6-dihydroxybenzoate (0.1002 g, 0.596 mmol) and tetrabutylammonium fluoride (TBAF) (0.3751 g, 1.190 mmol) in DMF (5 mL) was stirred under nitrogen atmosphere for 15 min.…”

Total syntheses of sesquiterpenes from Illicium species

“…57 Next, reduction of the a,b-unsaturated aldehyde 128 gave allylic alcohol 138. Johnson-Claisen rearrangement of the orthoester, generated from 138, resulted in formation of diastereomixture 127ab.…”