Recent Developments in Selected Sesquiterpenes: Molecular Rearrangements, Biosynthesis, and Structural Relationship among Congeners

Recent developments in selected sesquiterpenoids are reviewed for the past one decade (2005–2017) with special reference to Mechanisms of multistep molecular rearrangements of some sesquiterpenes or derivatives based on isotopic labeling studies and extensive spectroscopic analysis such as molecular rearrangement of acetyl cedrene to cedrene follower, acid catalyzed rearrangement of moreliane-based triketone, synthesis of (−)-isocomene and (−)-triquinane by acid-catalyzed rearrangement of (−)-modhephene, Total synthesis of (+)-cymbodiacetal, BF3 catalyzed molecular rearrangements of mono epoxides of α- and β-himachalenes, santonic acid: Zn-HCl-ether reduction. Insights into biosynthesis of albaflavenone, caryol-1(11)-ene-10-ol, (+)-koraiol, pogostol, patchouli alcohol and valerenadiene are discussed. Congeners for probing structure-biosynthetic relationship. This approach is discussed with the availability of very interesting results on the isolation of highly oxygenated secondary metabolites from endophytic fungi, Xylaria sp

Synthesis of olivacene, a constituent of <i>Archilejeunea olivacea</i>

2662-2664A simple synthesis of olivacene 1, a naturally occurring sesquiterpenoid hydrocarbon isolated from Archilejeunea olivacea has been described

Facile syntheses of 4-hydroxy-7-methyl-1-indanone, isolated from cyanobacterium Nostoc commune

1597-1599Two different high yielding synthetic routes both starting with 6-methylcoumarin 2 have been described to prepare 4-hydroxy-7-methyl-1-indanone 1, a constituent of cyanobacterium Nostoc commune having antibacterial activity. In the first route, methylative lactone ring opening of the coumarin 2 followed by catalytic hydrogenation of the cinnamyl double bond and subsequent PPA cyclization gives the methyl ether 5 of 1 which on demethylation gives 1 in excellent yield. Alternatively, catalytic hydrogenation of 2 followed by fusion with anhydrous AlCl₃ gives high yield of 1 in just two steps

Unusual KMnO₄oxidation product of β-ionone

1038-1041KMnO₄ oxidation of β-ionone has been reinvestigated. The structure proposed for the hydroxyionolactone 3 obtained in this reaction is supported by MS, UV, IR, ¹H and ¹³C NMR data and further confirmed by single crystal X-ray diffraction studies of the bromolactone 8