Chemical constituents of the nudibranch chromodoris marislae

The major metabolite of Chromodoris marislae, marislin ($\text{1a}$) was identified from spectral data and converted into the sponge metabolite pleraplysillin-2 ($\text{1b}$).     

Action of tert-butyl azidoformate on the conjugate bases of 1,2,3,4-tetrahydro-9H-carbazole and other indole derivatives

tert-Butyl azidoformate ($\text{2}$) reacts with the conjugate bases of $\text{3a}$, $\text{7a}$, $\text{9}$ (R¹ = R² = CH₃), and $\text{9}$ (R¹ = CH₃, R² = H) to give products [$\text{4}$, $\text{8}$, $\text{12}$, and $\text{14}$, respectively] in addition to the expected N-(tert-butoxycarbonyl)indole derivatives.     

Stereochemical consequence in the elimination of β-hydroxyalkylsilanes: Stereoselective formation of (Z)- and (E)-alkylidene-γ-butyrolactones

Titanium(IV) chloride-mediated reaction of 4,5-dihydro-2-(trimethylsiloxy)-3-(trimethylsilyl)furan (1a) with acetaldehyde gave $\text{diastereomerically pure}$ (3S^*, 1′R^*)-4,5-dihydro-3-(1′hydroxyethyl)-3-(trimethylsilyl)-2(3$\text{H}$)furanone (2a), which afforded selectively either (Z)- or (E)-α-ethylidene-γ-butyrolactone (3a) under proper conditions. Facile isomerization of 2a into $\text{diastereomerically pure}$ (3S^*, 1′R^*)-4,5-dihydro-3-&{1′-(trimethylsiloxy)ethyl}-2(3$\text{H}$)furanone (4) suggests an intriguing stereochemical outcome from 2a to (E)-3a via an enolate of 4.     

Chiral synthesis of (2s,3s,7s)-3,7-dimethylpentadecan-2-yl acetate and propionate,potential sex pheromone components of the pine saw-fly neodiprion sertifer (geoff.)

A synthesis of (2S,3S,7S)-3,7-dimethylpentadecan-2-yl acetate ($\text{2}$) and propionate ($\text{3}$) is described. (2S)-2-Methyldecan-1-yl lithium ($\text{5}$) was reacted with (3S,4S)-3,4-dimethyl-γ-butyrolactone ($\text{6}$) to yield the ketoalcohol $\text{19}$ which upon Huang-Minlon reduction furnished (2S,3S,7S)-3,7-dimethylpentadecan-2-ol ($\text{1}$). Acylations gave the esters $\text{2}$ and $\text{3}$. The (2S)-2-methyldecan-1-yl lithium was obtained via asymmetric synthesis. The chiral lactone $\text{6}$ was obtained from (2S,3S)-trans-2,3-epoxybutane and dimethyl malonate.     

New pseudo-one-dimensional metals: M2Mo6Se6 (M = Na,In, K,TI), M2Mo6S6 (M = K,Rb, Cs), M2Mo6Te6 (M = In,TI)

We present a new series of ternary chalcogenides, derived from divalent molybdenum: M₂Mo₆X₆. These compounds crystallize in a hexagonal lattice with a ≈ 9 Å, c ≈ 4.5 Å, and space group $\text{P6}{}_3\text{m}$. The compounds are characterized by clusters (Mo₃)¹_∞ in the form of linear chains, resulting from a linear condensation of Mo₆ octahedral clusters. The (Mo₃)¹_∞ clusters are well separated from each other, with the shortest MoMo intercluster distance larger than 6 Å. The resulting pseudo-one-dimensional structures show remarkable anisotropy of physical properties.     

2-cyano Δ3 piperidines vi1 : a general method for the stereoselective synthesis of cis and trans 2,6-dialkylpiperidine alkaloids

The cis 2,6-dialkylpiperidine alkaloid (±) dihydro-pinidine $\text{7b}$ and the trans alkaloid (±) solenopsin A $\text{5a}$ were synthesized from a common α-aminonitrile synthon $\text{1}$. The key step in this synthesis was the stereoselective reductive decyanation of the 1-benzyl-2cyano-2′, 6-dialkylpiperidines $\text{3a}$ and $\text{3b}$.     

Structure elucidation of AK-toxins,host-specific phytotoxic metabolites produced by alternaria kikuchiana tanaka

The structures of two host-specific phytotoxic metabolites, AK-toxin I and II, isolated from culture broth of Alternaria kikuchiana Tanaka (the fungus causing black spot disease of Japanese pear) were determined to be the ester consisting of N-acetyl-β-methyl-phenylalanine and 9,10-epoxy-8-hydroxy-9-methyl-2E, 4Z, 6E-decatrienoic acid ($\text{1}$) and its β-demethyl derivative ($\text{2}$).     

Ichthyotoxic sesterterpenoids from the neo guinean sponge carteriospongia foliascens

Six 20,24-dimethylscalarane derivatives ($\text{5}$, $\text{12}$, $\text{15}$, $\text{17}$, $\text{19}$, and $\text{21}$) have been isolated from the Neo Guinean sponge Carteriospongia foliascens. Compound $\text{12}$ is identical with a C₂₇ tetracyclic terpene previously isolated from an Australian specimen of the same sponge. The five other derivatives are new and their structures have been established on the basis of their spectral data. The structure of $\text{5}$ was confirmed by single-crystal X-ray diffraction and that of $\text{15}$ by chemical correlation with $\text{12}$. The configuration at C-4 for all these compounds has been determined through ¹³C NMR data. Evidence leading to reverse the configuration at this centre in previously reported C₂₇ tetracyclic terpenes is discussed. An ecological function is suggested for these molecules.     

A reinvestigation of asymmetric induction in diels-alder reactions to chiral acrylates.

The chiral induction in the Diels-Alder addition $\text{1}$ → $\text{2}$, assessed reliably by ¹⁹F-NMR-spectroscopy of the endo-esters $\text{4}$, varied between 47 - 93% in favor of the 2-(R)-adducts $\text{2}$ depending on the auxiliary chiral group and the Lewis-acid catalyst.     

The facile (<−50°C) formation of cis-bicyclo[6.1.0]nona-2,4,6-trienes from cyclonona-1,3,5,7-tetraenes: A symmetry - forbidden reaction

The formation of the $\text{cis}$-bicyclo [6.1.0] nona-2,4,6-trienes $\text{4a}$-$\text{c}$ is not due to the sequence $\text{1}$ → $\text{2}$ → $\text{4}$, which would involve the symmetry-forbidden reaction $\text{2}$ → $\text{4}$ even at ?50°C. Rather, reaction of RX at C^4–7 of $\text{5}$, which is formed together with $\text{1}$, leads (probably via $\text{6a}$-$\text{c}$ and $\text{7a}$-$\text{c}$ to $\text{4a}$-$\text{c}$.     

Plectranthoic acid A & B, two new triterpenoids from Plectranthus rugosus

Two new triterpenoid acids, designated as plectranthoic acid A and plectranthoic acid B, have been isolated from P. rugosus and are characterised as (20-S)-3α-hydroxy-18α,19α-$\text{H}\text{-}$-urs-12-en-30β-oic acid and (14-S)-3α-hydroxy-18α, 19α $\text{H}\text{-}$-urs-12-en-27α-oic acid.     

Studies on the La2−xSrxNiO4 (0 ⩽ x ⩽ 1) system

A new series of solid solutions of composition La_2?xSr_xNiO₄ (0 ? x ? 1) in which the oxidation state of nickel varies from +2 at x = 0 to +3 at x = 1 has been prepared. All the members of the system crystallize in the tetragonal K₂NiF₄ structure. The tetragonality ratio $\text{c}\text{a}$ shows a maximum at x = 0.5 which is interpreted as arising from a weak cooperative Jahn-Teller distortion due to octahedral site low-spin Ni³⁺ ions. The variation of electrical properties in the system is attributed to changes in electronic configuration of Ni³⁺.     

Structures of simarinolide and guanepolide (x-ray analysis), new quassinoids from Simaba cf orinocensis

Simarinolide $\text{4a}$ and Guanepolide $\text{5a}$ are new quassinoids with a C₂₅ basic skeleton isolated from a member of the French Guyanan Simaroubaceae, Simaba cf orinocensis H.B.K. The structure $\text{4a}$ was established by spectral means and that of $\text{5a}$ by X-ray diffraction analysis. The previously known simarolide $\text{1}$ was also isolated.     

Cavernicolin-1 and cavernicolin-2, epimeric dibromolactams from the mediterranean sponge aplysina (venongia) cavernicola

Cavernicolin-1 and Cavernicolin-2, two epimeric compounds having a γ-lactam ring fused to a dibromocyclohexenone ring, have been isolated from the Mediterranean sponge $\text{Aplysina}$$\text{(Verongia)}$$\text{cavernicola}$.     

Structure of plumbazeylanone: a novel trimer of plumbagin from plumbago zeylanica

Plumbazeylanone, a quinone from Plumbago zeylanica is probably 5b,11a,12,12a-tetrahydro-1,7-dihydroxy-5b-(8-hydroxy-3-methyl-1,4-naphthoquinon-2-yl)-5a,12a-dimethyl-5a$\text{H}$-dibenzo[$\text{b}$,$\text{h}$]fluorene-5,13:6,11-diquinone, a novel trimer of plumbagin with an additional methyl group.     

The crystal structures of α- and β-CdUO4

The structural parameters of α- and β-CdUO₄ crystals are determined by X-ray powder diffraction technique. α-CdUO₄ is rhombohedral and cell parameters are a = 6.233(3) Å and α = 36.12(5)°. β-CdUO₄ crystallizes in a C-centered orthorhombic cell with a = 7.023(4), b = 6.849(3), c = 3.514 (2) Å. The space groups are $\text{R}\text{3}\text{m}$ for α-CdUO₄ and Cmmm for β-CdUO₄. α-CdUO₄: 1U in (000), 1Cd in ($\text{1}\text{2}\text{1}\text{2}\text{1}\text{2}$), 2O(1) in ±(uuu), 2O(2) in ±(vvv); u = 0.113, v = 0.350, Z = 1. β-CdUO₄: 2U in ($\text{000;}\text{1}\text{2}\text{1}\text{2}\text{0}$), 2Cd in ($\text{1}\text{2}\text{0}\text{1}\text{2}\text{; 0}\text{1}\text{2}\text{,}\text{1}\text{2}$), 4O(1) in ($\text{0, ±y, 0;}\text{1}\text{2}\text{,}\text{1}\text{2}\text{±y, 0}$), 4O(2) in ($\text{±x, 0,}\text{1}\text{2}\text{;}\text{1}\text{2}\text{±x,}\text{1}\text{2}\text{,}\text{1}\text{2}$); x = 0.159, y = 0.278, Z = 2. β-CdUO₄ contains collinear uranyl UO²⁺₂ groups with a UO(1) distance of 1.91 Å, located either along or parallel to the c axis whereas the UO(1) bond length in α-CdUO₄ is 1.98 Å which is longer than the usual uranyl bond length.     

Botrydienal,a new prytotoxin,and its related metabolites,dehydrobotrydienal and deacetyldihydrobotrydial produced by botryotiniasquamosa

A new phytotoxin, botrydienal, and its two related metabolites, dehydrobotrydienal and deacetyldihydrobotrydial, were isolated from $\text{Botryotinia}$$\text{squamosa}$, and their structures were elucidated as $\text{1}$, $\text{2}$ and $\text{3}$, respectively, on the basis of spectral analysis.     

Ln(GaM2+)O4 and Ln(AlMn2+)O4 compounds having a layer structure [Ln = Lu,Yb, Tm,Er, Ho,and Y,and M = Mg,Mn, Co,Cu, and Zn]

A series of new compounds Ln(GaM²⁺)O₄ and Ln(AlMn²⁺)O₄ having a layer structure were successfully prepared [Ln = Lu, Yb, Tm, Er, Ho, and Y, and M = Mg, Mn, Co, Cu, and Zn]. The synthesis conditions and the unit cell parameters for 23 compounds have been determined. These compounds are isostructural with YbFe₂O₄ (space group $\text{R}\text{3}\text{m, a = 3.455(1)}$ Å, and c = 25.109(2) Å).     

Solid solution formation in chalcopyrite systems of the type AgInX2AgMIIIX2 where M = Al,Ga, and X = S,Se

Previous (1) work on ternary chalcopyrite solid solution formation has shown that the difference in end point axial ratios ($\text{Δc}\text{a}$) is an important factor in determining the extent of mutual solubility. It was concluded that when $\text{Δc}\text{a}\text{> 0.13}$ complete solid solubility will not occur. In this work it is shown that complete solid solution formation in the systems AgAlS₂AgInS₂ ($\text{Δc}\text{a}\text{= 0.111}$), AgGaS₂AgInS₂ ($\text{Δc}\text{a}\text{= 0.11}$) and AgAlSe₂AgInSe₂ ($\text{Δc}\text{a}\text{= 0.112}$) does occur. This shows that the value of $\text{Δc}\text{a}\text{= 0.13}$ as an upper limit for solid solution formation can be approached closely.     

New polyacetylenes from the sponge Siphonochalina sp.

Six new compounds, characterized by a long unsaturated alkyl chain (nC₂₂), were isolated from a marine sponge. All compounds except for one, possess an enyne terminus on one side of the molecule and either a terminal acetylene (in four) or a propargyl alcohol on the other end. Four of the compounds were unequivocally identified mainly by spectroscopic methods.Acetylenic compounds are well-known constituents of plants: only few, however, are known from marine organisms and to our knowledge only one group of compounds contains more than a single triple bond. Among the acetylene containing marine natural products are: A group of halogenated ethers, characterized by a straight-chain C-15 carbon skeleton and a terminal enyne function which has been isolated from algae¹ and a sea hare², carotenoids³, two steroids⁴, a sesquiterpene⁵ and polyketids^6,7.A diacetylene was found in a group of several n C-22 straight-chain compounds isolated from a marine sponge⁸. One of the compounds found in the latter sponge contains, again, the enyne terminus - an end group which turns out to be quite abundant in the above and the herewith discussed compounds.In our continuing search for bioactive compounds from marine organisms we have isolated from the sponge $\text{Siphonochalina sp}$.⁹ collected at several places in the southern part of the Gulf of Eilat (the Red Sea) six n C-22 straight-chain acetylenic compounds.Extraction of the freeze-dryed sponge (petrol ether, 4% dry weight) and subsequent repeated chromatographies (LH-20 and Silica gel)^10,11 gave six closely related new compounds, named in order of polarity, Δ¹⁵-docos-1-yne ($\text{1}$; RF^12a=0.65; 0.2% based on the dry weight of the animal), octahydrosiphonochalyne ($\text{2}$; Rf^12a=0.55; 0.4%), dihydrosiphonochalyne ($\text{4}$; Rf^12a=0.44; 0.1%) siphonochalyne ($\text{3}$; Rf^12b=0.34; 0.2%), dehydrosiphonochalynol ($\text{6}$; Rf^12b=0.55; 0.1%) and siphonochalynol ($\text{5}$; Rf^12b=0.43; 0.3%).