No abstract

One triterpenic acid (ursolic acid), one phenolic acid (rosmarinic acid), and four flavonoids (luteolin, luteolin 7-O-(6"-feruloyl)-β-glucopyranoside, luteolin 5-O-β-glucopyranoside, and luteolin 7-O-β-glucuronide) were isolated from the aerial parts of Thymus sipyleus subsp. sipyleus var. sipyleus and identified by spectroscopic methods. In vitro lipid peroxidation inhibition effects of the compounds were determined using TBA test method in a bovine brain liposome system. All compounds inhibited lipid peroxidation in various degrees except for ursolic acid. The order of the lipid peroxidation activities of luteolin, its glycosides and rosmarinic acid were: Luteolin 7-O-β-glucuronide> luteolin 5-O-β-glucopyranoside> luteolin 7-O-(6"-feruloyl)β-glucopyranoside > rosmarinic acid >luteolin. However, the activity order of the compounds was completely different in DPPH radical-scavenging activity. None of the compounds shows Fe 2+ chelating activity. The results were discussed based on their chemical structures and polarities.

Sonchus erzincanicus (Asteraceae) is an endemic species in Turkey, where six Sonchus species grow. In this study, a phytochemical study was performed on the aerial parts of the plant. The study describes the isolation and structure elucidation of five flavonoids and two α-ionone glycosides from S. erzincanicus. The compounds were isolated using several and repeated chromatographic techniques from ethyl acetate and aqueous phases that were partitioned from a methanol extract obtained from the plant. 5,7,3′,4′-Tetrahydroxy-3-methoxyflavone (1) and quercetin 3-O-β-D-glucoside (2) were isolated from the ethyl acetate phase, while corchoionoside C 6’-O-sulfate (3), corchoionoside C (4), luteolin 7-O-glucuronide (5) and luteolin 7-O-β-D-glucoside (6), apigenin 7-O-glucuronide (7) were isolated from the aqueous phase. Corchoionoside C 6’-O-sulfate (3), isolated for the first time from a natural source, was a new compound. The structures of the compounds were elucidated by means of 1H-NMR, 13C-NMR, 2D-NMR (COSY, HMQC, HMBC) and ESI-MS.

A new and stereospecific synthesis for conduritol-A has been developed starting from cyclohexa-l,4-diene where hydroxy groups have been introduced by classical KMn04-oxidation followed by photo-oxygenation; suitable ring-opening reactions gave the desired conduritol-A.Conduritols and aminoconduritols are interesting potential inhibitors for Glycosidases.1 In 1908 Kubler2 isolated from the bark of the vine Marsdenia condurango the first known cyclohexenetetrol which was named as conduritol. j. The correct configuration of this isomer was later established by Dangschat and Fischer.3 The first successful and non-stereospecific synthesis of conduritol-A was carried out by Nakajima et aL4 starting from trans-benzenediol. More recently, Knapp et al.5 described a stereospecific synthesis of the naturally occurring conduritol-A using p-benzoquinone in a multistep sequence. Herewith, we describe a novel, efficient and stereospecific synthesis of conduritol-A starting from the readily available cyclohexa-l,4-diene. Our synthetic strategy is based on the introduction of two oxygen functionalities at the C2 and C3 positions by KMn04-oxidation and the other two oxygen functionalities at the C1 and C4 positions by photo-oxygenation.6The key compound, (2), in the synthesis of conduritol-A was synthesized by bromination of cyclohexa-l,4-diene followed by KMn04-oxidation as described in the literature.7 The resulting cis-diol was protected by ketal formation with 2,2-dimethoxypropane. Dehydrobromination with DBU (1 ,8diazabicyclo[5.4.0]undec-7-ene) provided (2) in high yield. Photo-oxygenation of (2) in CC14 (150 W, projection lamp) at room temperature using tetraphenylporphyrin as the sensitiser, followed by silica gel chromatography afforded (3) in a yield of 95%. 1H and 13C n.m.r. spectra revealed suprisingly the formation of only one isomer. A six-line 13C n.rn.r. spectrum is in good agreement with the structure (3), which possesses a symmetry element. On the basis of the spectral data we were not able to predict the exact configuration of the molecule. We assume that singlet oxygen approaches the diene unit from the sterically less crowded face of the molecule to form the anti-adduct. The exact configuration was determined at the final step. For additional structural proof we have relied on chemical transformations such as the cobalt-mesotetraphenylporphyrin (CoTPP) catalysed reaction.8 We sub-

Photooxygenation of 1,4-cyclohexadiene afforded hydroperoxy endoperoxides 3 and 4 in a ratio of 88:12. Reduction of 3 with LiAlH(4) or thiourea followed by acetylation of the hydroxyl group and KMnO(4) oxidation of the double bond gave proto-quercitol 10b. Application of the same reaction sequences to 4 resulted in the formation of gala-quercitol 14. Quercitols were easily obtained by ammonolysis of acetate derivatives in MeOH. The outcome of dihydroxylation reactions were supported by conformational analysis.