Enantioselective 1,3-Dipolar Cycloaddition Reaction of Nitrones with α-(Acyloxy)acroleins Catalyzed by Dipeptide-Derived Chiral Tri- or Diammonium Salts

Organoammonium salts of dipeptide-derived chiral tri-amines or diamines with TfOH catalyzed the enantioselective 1,3-dipolar cycloaddition reactions of alpha-acyloxyacroleins with nitrones to give the corresponding adducts in good yields (up to 96%) and with high diastereo- and enantioselectivities (up to 89% ee). Although alpha-(p-methoxybenzoyloxy)acrolein is rather unstable under the reaction conditions, alpha-(3-pyrroline-1-carbonyloxy)acrolein is stable enough to be smoothly converted into the corresponding adducts with the aid of the chiral organoammonium salt catalysts

Taichunamides: Prenylated Indole Alkaloids from Aspergillus taichungensis (IBT 19404)

Seven new prenylated indole alkaloids, taichunamides A–G, were isolated from the fungus Aspergillus taichungensis (IBT 19404). Taichunamides A and B contained an azetidine and 4‐pyridone units, respectively, and are likely biosynthesized from notoamide S via (+)‐6‐epi‐stephacidin A. Taichunamides C and D contain endoperoxide and methylsulfonyl units, respectively. This fungus produced indole alkaloids containing an anti‐bicyclo[2.2.2]diazaoctane core, whereas A. protuberus and A. amoenus produced congeners with a syn‐bicyclo[2.2.2]diazaoctane core. Plausible biosynthetic pathways to access these cores within the three species likely arise from an intramolecular hetero Diels–Alder reaction.Sieben neue prenylierte Indolalkaloide wurden aus A. taichungensis isoliert. Dieser Pilz erzeugt Alkaloide mit anti‐Bicyclo[2.2.2]diazaoctan‐Kern, während A. protuberus und A. amoenus syn‐Derivate herstellen. Die Strukturdiversität der von Tryptophan abgeleiteten Sekundärmetaboliten deutet auf stereochemisch und strukturell hoch entwickelte Synthesefunktionen für Sekundärmetaboliten in diesen orthologen Pilzen hin.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/137451/1/ange201509462.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137451/2/ange201509462-sup-0001-misc_information.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137451/3/ange201509462_am.pd

Reticulatins A and B and hyrtioreticulin F from the marine sponge Hyrtios reticulatus

Three new alkaloids, reticulatins A (1) and B (2) and hyrtioreticulin F (3), were isolated from the water-soluble fraction of an EtOH extract of the marine sponge Hyrtios reticulatus. Compounds 1 and 2 were found to be novel 1,3-dimethyl-5-(methylthio)imidazolium alkaloids. The structure of 3 was determined to be an indole alkaloid related to hyrtioreticulin E (8) and hyrtioerectine B (9), which were isolated previously from the n-BuOH-soluble fraction of the sponge extract. The presence of three NH units in 3 was indicated by the 1H–15N HSQC spectrum in D2O/H2O (5:95) containing 0.05% TFA measured at 5 °C. Compound 3 is likely biosynthesized from l-tryptophan, two units of l-alanine, and glycine by the Pictet–Spengler reaction. The absolute configurations of 1–3 were determined by the methods based on ECD spectra. In addition, the result for 1 was further confirmed by the PGME method

Fluorescence detected circular dichroism of a red-shifted exciton-coupling chromophore N,N'-carbonyl-bridged dipyrrinone derivative using an ellipsoidal device

A fluorescent red-shifted exciton-coupling chromophore, N,N'-Carbonyl-bridged dipyrrinone, was subjected to fluorescence-detected CD (FDCD) measurements as a primitive structure-elucidating probe with trans-1,2-cyclohexanediol template in several solvents under various instrumental conditions. With the help of a JASCO ellipsoidal mirror device FDCD465, a chloroform solution achieved the sensitivity enhancement by 50 times of the transmission CD and 5 times of the conventional FDCD. All FDCD spectra were completely free from the polarization artifacts

Altercrasins A–E, Decalin Derivatives, from a Sea-Urchin-Derived <i>Alternaria</i> sp.: Isolation and Structural Analysis Including Stereochemistry

In order to find out the seeds of antitumor agents, we focused on potential bioactive materials from marine-derived microorganisms. Marine products include a number of compounds with unique structures, some of which may exhibit unusual bioactivities. As a part of this study, we studied metabolites of a strain of Alternaria sp. OUPS-117D-1 originally derived from the sea urchin Anthocidaris crassispina, and isolated five new decalin derivatives, altercrasins A&#8211;E (1&#8211;5). The absolute stereostructure of altercrasins A (1) had been decided by chemical transformation and the modified Mosher&#8217;s method. In this study, four decalin derivatives, altercrasins B&#8211;E (2&#8211;5) were purified by silica gel chromatography, and reversed phase high-performance liquid chromatography (RP HPLC), and their structures were elucidated on the basis of 1D and 2D nuclear magnetic resonance (NMR) spectroscopic analyses. The absolute configuration of them were deduced by the comparison with 1 in the NMR chemical shifts, NOESY correlations, and electronic circular dichroism (ECD) spectral analyses. As a result, we found out that compound pairs of 1/2 and 4/5 were respective stereoisomers. In addition, their cytotoxic activities using murine P388 leukemia, human HL-60 leukemia, and murine L1210 leukemia cell lines showed that 4 and 5 exhibit potent cytotoxicity, in especially, the activity of 4 was equal to that of 5-fluorouracil

New oxygenated himachalenes in male-specific odor of the Chinese windmill butterfly, <i>Byasa alcinous</i><i>alcinous</i>

<div><p>Male adults of the Chinese windmill <i>Byasa</i><i>alcinous</i><i>alcinous</i> (Papilionidae) are well known to have a strong musk-like odor, in which two oxygenated himachalene compounds, together with six sesquiterpene hydrocarbons, were newly discovered. γ-Himachalen-4-yl acetate (<b>1</b>) was the predominant compound isolated from the solvent extract of the males. The structure of <b>1</b> was determined using MS and NMR, and its relative configuration was established as 1<i>S</i>^*,4<i>R</i>^*,6<i>R</i>^* by NOE analysis with the help of quantum mechanical computation. Interestingly, the amount of <b>1</b> in males increased until 7 days after eclosion, suggesting that this compound is involved in sexual maturation for mating. Another new compound was identified as γ-himachalen-4-ol (<b>2</b>) by comparison with the retention time and mass spectrum of the hydrolysate of <b>1</b>. Since males of other papilionid species have general volatiles omnipresent in plants and insects, the presence of species-specific volatiles in males is characteristic of <i>B. alcinous alcinous</i>.</p></div

Assignment of Absolute Configuration of Bromoallenes by Vacuum-Ultraviolet Circular Dichroism (VUVCD)

A new application of vacuum-ultraviolet circular dichroism (VUVCD), which enables the measurement of CD spectra in the vacuum-ultraviolet region (140-200 nm), for the assignment of the absolute configurations of bromoallenes is described. Bromoallene moieties are found in natural products obtained from many marine organisms. To date, the absolute configuration of bromoallenes has been assigned almost exclusively with Lowe's rule, which is based on specific rotation. However, exceptions to Lowe's rule have been reported arising from the presence of other substituents with large specific rotations. For the unambiguous assignment of the absolute configuration of the bromoallene moiety with its characteristic absorption wavelength at 180-190 nm due to the pi-pi* transition, VUVCD was applied to four pairs of bromoallene diastereomers prepared by modifying the synthetic scheme of omaezallene. The VUVCD spectra clearly showed positive or negative Cotton effects around 180-190 nm according to the configuration of the bromoallene employed, revealing the potential of VUVCD for determining absolute stereochemistry

HPLC profiles and spectroscopic data of cassane-type furanoditerpenoids

The data presented here are related to the research paper entitled “Hydroxylated furanoditerpenoids from the pupal case produced by the bruchid beetle Sulcobruchus sauteri inside the seed of Caesalpinia decapetala” (Akihara et al., 2018) [1]. In this data article, we provide high-performance liquid chromatography (HPLC) profiles of seven undescribed hydroxylated furanoditerpenoids, caesalsauteolide, 2-hydroxycaesaljapin, 2,7-dihydroxycaesaljapin, 2-hydroxycaesalacetal, caesalsauterol, 6-acetylcaesalsauterol, norcaesalsauterol isolated from the pupal cases produced by Sulcobruchus sauteri and four known compounds, caesaljaponin A (Kamikawa et al., 2015) [2], caesaljaponin B (Kamikawa et al., 2015) [2], caesalacetal (Kamikawa et al., 2016) [3], and caesaljapin (Kamikawa et al., 2016; Ogawa et al., 1992) [3,4] isolated from the cotyledons of the intact seeds of Caesalpinia decapetala. Besides, 1D NMR, 2D NMR, and HRESIFTMS data of the seven undescribed furanoditerpenoids are also presented. Keywords: Sulcobruchus sauteri, Caesalpinia decapetala, Cassane diterpenoid, HPLC, NMR, ESIM