Synthesis of (±)-africanol

Abstract

Os compostos 1a e 1b, diastereoisômeros do africanol, foram obtidos como produtos exclusivos através de uma metodologia que empregou como etapa chave a reação de ciclização intramolecular, mediada por n BuLi, do iodeto vinílico 5. Utilizando processo de ciclização semelhante com o composto 19, obteve-se o álcool terciário 20 como único produto. O africanol pode ser obtido, juntamente com seus diastereoisômeros 1a e 1b, ao se efetuar a reação de ciclização intramolecular da cetona 21, em presença de iodeto de samário. Two diastereomers of africanol, compounds 1a and 1b, were obtained exclusively through a methodology which employed, as the key step, the n BuLi mediated intramolecular cyclization of the vinyl iodide 5. A similar cyclization of 19 provided exclusively the tertiary allylic alcohol 20. Africanol could be prepared, along with its diastereomers 1a and 1b, when ketone 21 was submitted to the cyclization reaction promoted by samarium iodide.

Structure Confirmation of a Bioactive Lactone Isolated from Otoba parvifolia through the Synthesis of a Model Compound

“…The organic extracts were combined and washed with 10% (w/w) Na 2S2O3 (2 × 10 mL) and saturated brine (2 × 10 mL) and dried over MgSO4. After filtration the solvent was removed under reduced pressure and the product was purified by flash chromatography using hexane/ethyl acetate ( (6), 321 (7), 277 (3), 211 (100), 167 (14), 157 (5), 149 (8), 113 (10), 99 (9), 69 (9); HRESIMS m/z 339.0240 [M + H] + (calcd for C11H16IO4, 339.0094).…”

“…The double alkylation of cyclohexenone was carried out under kinetic conditions and in the presence of HMPA, 5 affording compound 6 in 82% yield for the two steps. When ketone 6 was treated with ethylene glycol in the presence of PTSA in benzene, 6 a mixture of ketals 7 and 8 was obtained in a 9.5:1 ratio, as determined by GC. The regioisomers were separated by flash chromatography and the migration of the double bond was confirmed by the 1 H NMR spectrum of the major compound, which showed a multiplet for the vinylic hydrogens.…”

Total Syntheses of (±)-Omphadiol and (±)-Pyxidatol C through a Cis-Fused 5,7-Carbocyclic Common Intermediate

“…Further structural complexities of the two terpenoids involve a panel of contiguous stereogenic centers within the trans -fused 5,7-carbocycle. Dense stereochemical complexity on a relatively flexible skeleton and difficult levels of oxidation have rendered africananes containing such structural motifs to be appealing synthetic targets and have inspired elegant synthetic solutions to this family of terpenoids. − …”

Total Synthesis of (+)‐Omphadiol

“…Comparison with structurally similar terpenoids, including pyxidatol (2) and africanol (not shown), [2] reveals a large family of sesquiterpenes and diterpenes that share a common tetrasubstituted cyclopentane ring (highlighted in red). Notably, many of these natural products display potent biological activities.…”

“…[1] As a member of the africanane family of sesquiterpenes, which all possess a 5-7-3 tricyclic core, omphadiol contains six contiguous stereogenic centers, which makes it a challenging synthetic target. Comparison with structurally similar terpenoids, including pyxidatol (2) and africanol (not shown), [2] reveals a large family of sesquiterpenes and diterpenes that share a common tetrasubstituted cyclopentane ring (highlighted in red). Notably, many of these natural products display potent biological activities.…”