Biphenyl ether and biphenyl quinolizidine lactone alkaloids from Heimia salicifolia

Three new biphenyl ether quinolizidine lactone alkaloids (1–3) and 13 new biphenyl quinolizidine lactone alkaloids (4–16) were isolated from Heimia salicifolia (Lythraceae) together with seven known alkaloids. Their structures were determined by spectroscopic analyses and chemical conversions.     

First total synthesis of cyclic pentadepsipeptides Hikiamides A–C

The first total syntheses of naturally occurring cyclodepsipeptides Hikiamides A–C are described. The key linear pentapeptide precursors, prepared efficiently via Fmoc-solid-phase synthesis, were cyclized in dilute solution to provide the target Hikiamides A–C. The structures of the synthetic Hikiamides A–C were characterized by NMR and HRMS spectroscopy which were in agreement with those of natural products.     

Determination of ppt levels of atmospheric volatile organic compounds in Yakushima, a remote south-west island of Japan

An analytical method was utilized to detect ppt levels of VOCs in air. The method was based on the US-EPA method TO-14, consisting of canister sampling, three module enrichment and GC/MS analysis. Target compounds included chlorofluorocarbons (four kinds), benzene and its derivatives (14), halogenated hydrocarbons (20), and others (three). The minimum detection limits of the method for the target compounds ranged from 0.016 to 0.040 ppb (0.06–0.23 μg/m³). The recoveries of the target compounds ranged from 77 to 113% and relative coefficients of variation (n=4) were 3.0–9.0%. The sampled air was stable for at least 14 days after pressurizing with humidified nitrogen gas at 200 kPa (absolute pressure). The method was applied to analyze the VOCs in the air of Yakushima, a remote island of south-west Japan where no distinct local pollution source is considered.     

Chloroprene as a source of fine chemicals: palladium-catalyzed synthesis of terminal allenes

[reaction: see text] Several functionalized terminal allenes were prepared in moderate to excellent yield by a palladium-catalyzed reaction of chloroprene (2-chloro-1,3-butadiene) with soft nucleophiles.     

Application of 1,2,3,5,6,7-hexahydropyrrolizinium perchlorate in the synthesis of 7a-substituted hexahydro-1h-pyrrolizines

The method for preparing 7a-substituted hexahydro-1H-pyrrolizines 2 from 1,2,3,5,6,7-hexahydropyrrol-izinium Perchlorate (3) was investigated, by which introduction of a wide variety of functionalities on C(7a) could be achieved easily.     

The inclusion complex of piromidic acid with dimethyl-β-cyclodextrin in aqueous solution and in the solid state

Inclusion complex formation of piromidic acid (PA) with dimethyl--cyclodextrin (DM--CD) in aqueous solution and in the solid state was confirmed by the solubility method, differential scanning calorimetry (DSC) and proton nuclear magnetic resonance (¹H-NMR) spectroscopy. The apparent stability constant,K _c , of the complex was estimated to be 244 M^–1. The stoichiometry of the complex was given as the ratio 1:2 of PA to DM--CD. The dissolution rate of the PA/DM--CD complex was much greater than that of intact PA.Presented at the Fourth International Symposium on Inclusion Phenomena and the Third International Symposium on Cyclodextrins, Lancaster, U.K., 20–25 July 1986.     

Reaction potential map analysis of site selectivity of acrylic acid and acrylonitrile

The reaction potential map (RPM) method has been extended so that the molecular reactivity towards nucleophiles can be analyzed. An anion consisting of the nucleus with + 1 charge and a pair of electrons was adopted as the model nucleophile. From the interaction energy between a substrate and this model particle, RPM and its component maps were obtained. With respect to practical applications, the reactivities of acrylic acid and acrylonitrile towards nucleophiles were examined. In these molecules, the exchange interaction as well as the charge-transfer interaction were found to be very important in the elucidation of the observed site selectivity.     

Diastereo- and Enantiocontrolled Synthesis of (–)-Allosedamine via Cycloaddition of a Chiral Nitrone

The piperidine alkaloid (–)-allosedamine ( 1 ) has been synthesized, in 21% overall yield, in nine steps starting from the formyl-ester 4 . The synthesis features the reaction cascade 7 → 3 → 2 , involving asymmetric electrophilic enolate hydroxyamination, hydroxylamine/aldehyde condensation, and nitrone/styrene cycloaddition, as well as the reductive N/O cleavage-decyanation 12 → 1 .