Two new angular methyl dioxygenated D:A-fried-oleananes

Two new trioxygenated D:A-friedo-oleananes from Elaeodendron glaucum have been shown to be the angular methyl dioxygenated 25,28-dihydroxy-D:A-friedo-oleanan-3-one(1) and 3,28-dioxo-D:A-friedo-oleanan-25-ol(2) by interconversion and deoxygenation of the alcohol(2) using Lithium-ethyle diamine reduction coupled with spectroscopic methods.     

Assignment of the 13C nuclear magnetic resonance spectra of three 27-hydroxyfriedelanes

¹³C NMR spectra of 27-hydroxyfriedelane, kokoonol (27-hydroxyfriedelan-3-one) and kokoononol (27-hydroxyfriedelan-3,21-dione) have been recorded and signals assigned using the off-resonance decoupling, inversion recovery and lanthanide induced shift techniques.     

Ferroelectric characteristics of MFIS structure with P(VDF–TrFE)/BaTiO3 nanocomposite as ferroelectric layer

A metal–ferroelectric–insulator–semiconductor (MFIS) structure has been made using poly(vinylidene difluoride–trifluoroethylene)/barium titanate [P(VDF–TrFE)/BaTiO₃] nanocomposite as ferroelectric layer, on silicon/silicon dioxide (Si/SiO₂) substrate. Different concentrations of BaTiO₃ were added to P(VDF–TrFE) polymer using bath sonication method, and the films were prepared using spin coating method. The structure was annealed to 120 °C for 2 h and then the top aluminium electrode was deposited by thermal evaporation method. Capacitance–voltage shows an increase in accumulation capacitance as the BaTiO₃ nanoparticle concentrations increases. Dielectric constant was estimated from the capacitance voltage (C–V) characteristics and found to be changing as the concentration of BaTiO₃ is varied. Polarization–electric field analyses show hysteresis behaviour of the nanocomposite. A comparison of MFIS and metal–ferroelectric–semiconductor structures was done with varying ferroelectric film thicknesses. All these results suggest that this polymer nanocomposite can be a promising material which can be used in non-volatile memory devices.     

Carbon-13 n.m.r. study of naturally occurring xanthones

The ¹³C n.m.r. spectra of 36 naturally occurring xanthones are reported and all chemical shifts assigned. The shifts in substituted xanthones can be predicted from substituent effects evaluated for simple derivatives. The agreement between calculated and observed shifts decreases as the extent of substitution in the xanthone increases.     

Structures of kokzeylanol and kokzeylanonol two new natural tri- and tetra- oxygenated D:A-friedo-oleananes

Kokzeylanol and kokzeylanonol obtained from $\text{Kokoona}$$\text{zeylanica}$ have been shown to be 6β,27-dihydroxy-D:A-friedo-olean-3-one ($\text{1}$) and 6β,27-dihydroxy-D:A-friedo-oleana-3,21-dione ($\text{2}$), respectively by the deoxygenatlon of their 27-acetoxy derivatives using Lithium-ethylene diamine reduction coupled with spectroscopic and irradiation methods. Kokzeylanonol represents the first tetraoxygenated D:A-friedo-oleanane isolated from a natural source.     

The structure of zeylasterone - the first of a new series of phenolic 24-nor-D:A-friedo-oleanan triterpenes

Zeylasterone, a new triterpene from Kokoona zeylanica, is shown to be 2,3-dihydroxy-6-oxo-24-nor-D:A-friedo-oleana-1,3,5(10),7-tetraen-23,29-dioic acid-29-methyl ester (20 α) ($\text{1}$), the first member of a new series of phenolic 24-nor-D:A-friedo-oleanans.     

Calozeylanic acid,a new bark acid from three calophyllum species (guttiferae)

Calozeylanic acid has been isolated from the bark of three $\text{calophyllum}$ species: $\text{C.lankaensis}$ (= $\text{C.zeylanicum}$), $\text{C.thwaitesii}$ and $\text{C.walkeri}$. Its structure has been established as 2(R),3(R)-2,3-Dimetyl- 5-hydroxy-6-(3-methylbutanyl)-6-(3,7-dimethylocta-3,6-dienyl)-7-oxo-8- (2-carboxy-1-phenylethyl)-2,3,6,7-tetrahydrobenzo-4-pyrone.     

Structures of three new 6β-hydroxy di- and tri-oxygenated friedelane triterpenes from kokoonazeylanica thw. (celastraceae)

Three new triterpenes zeylanol, zeylanonol and zeylandiol isolated from $\text{Kokoona}$$\text{zeylanica}$ have been identified as 6β-hydroxyfriedelan-3-one, 6β-hydroxyfriedelan-3,21-dione and 6β,21β-dihydroxyfriedelan-3-one, respectively by spectroscopic methods and chemical interconversions.     

13C nuclear magnetic resonance spectra of some naturally occurring friedelanones

¹³C NMR spectra of friedelan, friedelan-21-one, friedelan-6-one, friedelane-321-dione, friedelane-3,6-dione and friedelane-3,6,21-trione have been recorded and signals assigned using off-resonance decoupling, inversion recovery and lanthanide induced shift techniques.