bluuebunny/crossref_metadata_2025_split huggingface dataset:
Use of 2‐cyano‐1,1‐dimethylethyl as a protecting group in the synthesis of DNA VIA phosphite intermediates
Authors: Marugg J. E. , Dreef C. E. , van der Marel G. A. , van Boom J. H. 
Published: September 2010

AbstractThe phosphitylating agent 2‐cyano January ‐dimethylethoxy dichlorophosphine and its mono‐N‐morpholino derivative proved to be suitable for the synthesis of DNA in solution and on a solid support. The 2‐cyano‐l,l‐dimethylethyl for protecting P‐0 could be removed selectively under mildly basic conditions.
Convenient conversions of codeine into 6‐demethoxythebaine via bond rearrangement (Chemistry of Opium Alkaloids, Part XVIII)
Authors: Beyerman H. C. , Crabbendam P. R. , Lie T. S. , Maat L. 
Published: September 2010

AbstractTwo syntheses are described of (‐)‐6‐demethoxythebaine (4), both starting from the 6‐O‐mesyl**** derivative 2 of (‐)‐codeine. Treatment with sodium hydride in toluene gives (‐)‐6‐demethoxythebaine in 60% yield. The preparation via 8β‐bromo‐6,7‐didehydro‐4,5‐epoxy‐3‐methoxy‐17‐methylmorphinan (3), which is obtained from the mesyl derivative with the aid of lithium bromide, has an overall yield of 80%.
Synthesis of the mirror image of β‐D‐riboguanosine 5′‐phosphate a substrate to study chiral selection in non‐enzymatic RNA synthesis
Authors: Visser C. M. , van Westrenen J. , van Boom J. H. , van Boeckel C. A. A. 
Published: September 2010

Abstractβ‐L‐Riboguanosine 5′‐phosphate (5′pLG) was prepared by transglycosidation of properly protected L‐ribose and guanine derivatives followed by phosphorylation and removal of all protecting groups. Experiments indicated that 5′pDG was selected from a mixture of L and D isomers in template directed oligomerization of RNA.
Photochemical reaction of some aromatic thiones with aryl‐ and alkyl‐substituted (methylthio)acetylenes. The (2+2)‐cycloaddition products and the occurrence of the equilibrium thiete ⇋ α, β‐unsaturated thioxo compound
Authors: Brouwer A. C. , Bos H. J. T. 
Published: September 2010

AbstractUpon irradiation (λ > 525 nm), xanthenethione2oand thioxanthenethione2sreact in a non‐regiospecific manner with the triple bond of the acetylenes6a(Ph‐C≡C‐SCH3) and6b[(2‐thienyl)–C≡C‐SCH3] to produce in each case the two possible (2 + 2)‐cycloaddition products, which were isolated as thietes or α,β‐unsaturated thioxo compounds. In a solution of each of these reaction products, spectroscopic results confirmed the occurrence of the equilibrium thiete ⇋ α, β‐unsaturated thioxo compound. With acetylene6c(t‐Bu‐C≡C‐SCH3), the photochemically excited thiones2oand2sgave, in each case, only the (2 + 2)‐cycloaddition product8. In solution these thietes8do not equilibrate with the corresponding α, β‐unsaturated thiones. Surprisingly, no products could be isolated or detected after irradiation of thiobenzophenone2hin the presence of acetylenes6aor6b.
A Copper(I)‐catalyzed photochemical cyclodimerization of 1, 3, 5‐hexatriene
Authors: Bos H. J. T. , Elferink V. H. M. , van der Ploeg D. 
Published: September 2010

AbstractIrradiation of neat 1, 3, 5‐hexatriene with light (λ > 334 nm) in the presence of 0.2 mol% of copper(I) trifluoromethanesulfonate affords a mixture of three dimerization products in an overall yield of 80%, consisting of 86% 4‐(E‐1, 3‐butadienyl‐3‐vinyl‐1‐cyclohexene 2˜(cis 2˜/trans2˜∼ 1˜) and 14% 1Z, 3E, 7E, 9Z‐1, 3, 7, 9 ‐cyclododecatetraene 3˜.
The synthesis of α‐amino‐substituted diphenylphosphine oxides
Authors: Broekhof N. L. J. M. , van Elburg P. , van der Gen A. 
Published: September 2010

AbstractFour methods with differing but overlapping specificity are described for the synthesis of α‐unsubstituted as well as α‐substituted (aminomethyl)diphenylphosphine oxides. The first method is based on the Arbusov reaction, the second on a Mannich‐type condensation of diphenylphosphine oxide [Ph2P(O)H] with aldehydes and secondary amines, the third on the addition of Ph2P(O)H to enamines and the fourth on the reaction of anions derived from α‐unsubstituted (aminomethyl)diphenylphosphine oxides with various electrophiles.
Studies on polypeptides XLI1H NMR studies of non‐covalent, semi‐synthetic ribonuclease A analogues in which histidine‐119 has been replaced by L‐homohistidine, Nτ‐methyl‐L‐histidine, Nπ‐methyl‐L‐histidine and 3‐(3‐pyrazolyl)‐L‐alanine, respectively
Authors: Serdijn J. , Bloemhoff W. , Kerling K. E. T. , Havinga E. 
Published: September 2010

Abstract1H NMR titration studies carried out at 300 or 360 MHz are described for RNase 1–120, RNase 1‐118 and five non‐covalent complexes of RNase 1‐118/RNase 111‐124, having L‐histidine, L‐homohistidine, L‐Nπ‐methylhistidine, L‐τ‐methyl‐histidine and 3‐(3‐pyrazolyl‐L‐alanine, respectively, as the active‐site amino acid in position 119. The pH titrations were performed both in the absence and in the presence of a RNase A inhibitor (3′‐CMP). From least‐squares analysis of the titration data, the most probable pKa values and intrinsic chemical shifts of the histidine side‐chain in position 12 and 105 and of the amino acid residue in position 119 were obtained. On the basis of these results, the effects of replacing the amino acid residue in position 119 and of inhibitor binding are discussed.
A convenient synthesis of fecapentaene‐12 by the Horner‐Wittig reaction
Authors: de Wit P. P. , van Schaik T. A. M. , van der Gen A. 
Published: September 2010

AbstractA synthesis of racemic fecapentaene‐12 and other glyceryl enol ethers has been developed based on the Horner‐Wittig reaction. Coupling of the anion of the glyceryl substituted phosphine oxide 7˜ with unsaturated aldehydes 9a˜‐c˜ provided, after treatment with base, the silyl protected glyceryl enol ethers 11a˜‐c˜. The silyl groups were easily removed and mixtures of E and Z isomers of glyceryl enol ethers 12a˜‐c˜ were obtained. The isomers could be separated upon washing with ether/hexane.
Synthesis of the glycotripeptide alanyl‐(O‐β‐D‐galactopyranosylseryl)‐alanine using (9‐fluorenylmethoxy)carbonyl and esters of 2‐(hydroxymethyl)‐9,10‐anthraquinone as temporary protecting groups
Authors: Hoogerhout P. , Guis C. P. , Erkelens C. , Bloemhoff W. , Kerling K. E. T. , van Boom J. H. 
Published: September 2010

AbstractThe cesium salts of N‐[(9‐fluorenylmethoxy)carbonyl]‐L‐serine (Fmoc‐Ser, 1a)*** and ‐L‐threonine (Fmoc‐Thr, 1b) were treated with 2‐(bromomethyl)‐9,10‐anthraquinone (Maq‐Br), yielding Fmoc‐Ser‐OMaq (2a, 79%) and Fmoc‐Thr‐OMaq (2b, 74%). HgBr2‐catalyzed glycosylation with 2,3,4,6‐tetra‐O‐acetyl‐α‐D‐galactopyranosyl bromide gave Fmoc‐Ser(Ac4βGal)‐OMaq (3a, 89%) and Fmoc‐Thr(Ac4βGal)‐OMaq 13b, 53%). Fmoc‐Ser(Ac4βGal)‐OH (4), obtained by reaction of 1a with Na2S2O4 (88%), was condensed with H‐Ala‐OMaq using the DCC/HOBt method (83%). The Fmoc‐Ser(Ac4βGal)‐Ala‐OMaq(5), thus obtained, was Nα‐deprotected with morpholine and coupled with Fmoc‐Ala using water soluble carbodiimide in the presence of HOBt to yield Fmoc‐Ala‐Ser(Ac4βGal)‐Ala‐OMaq (6, 59%). The fully deprotected glycotripeptide (8) was obtained from 6 by successive treatment with Na2S2O4, morpholine and hydrazine hydrate (81%).The compounds 3a, 6 and 8 were characterized using correlated 300 MHz 1H NMR spectroscopy (2D‐COSY).
Biomimetic total synthesis of steroids, IX. Stereospecific synthesis of C‐homo‐19‐norsteroids
Authors: Groen M. B. , Hindriksen B. , Zeelen F. J. 
Published: September 2010

AbstractCationic cyclization of 2‐[7‐(3‐methoxyphenyl)‐(E)‐4‐heptenyl]‐3‐methyl‐2‐cyclopentenol (1c) produced 3‐methoxy‐17‐methyl‐C‐homo‐1,3,5(10),13(17)‐gonatetraene (3c) and its 1‐methoxy isomer 2c. Epoxidation of 3c with tert‐butyl hydroperoxide in the presence of molybdenum hexacarbonyl produced the corresponding 13α, 17α‐epoxide 14 as the major product, which, in three steps, was converted into C‐homo‐1,3,5(10)‐estratriene‐3,17β‐diol (18).
1,6‐Anhydro‐2,3‐O‐(4‐methoxybenzylidene)‐β‐D‐mannopyranose: A useful synthon for the preparation of valuable disaccharides
Authors: Kloosterman M. , de Nijs M. P. , van Boom J. H. 
Published: September 2010

AbstractSubstitution of the 2‐O‐triflyl function in 4‐O‐acetyl‐1,6‐anhydro‐3‐O‐anisoyl‐β‐D‐mannopyranose with the Cs‐salt of levulinic or benzoic acid affords 4‐O‐acetyl‐1, 6‐anhydro‐3‐O‐anisoyl‐2‐O‐levulinoyl(benzoyl)‐β‐D‐glucopyranoses. Coupling of 1,6‐anhydro‐2,3‐O‐(4‐methoxybenzylidene)‐β‐D‐mannopyranose with β‐D‐galactose pentaacetate in the presence of trimethylsilyl triflate affords a β(1→4) linked disaccharide the mannose unit of which can be converted into the 3‐O‐anisoyl‐2‐O‐levulinoyl‐(benzoyl) protected glucose moiety.
Investigations into the total synthesis of momilactones. Stereoselective preparation of (±)‐4,4‐dinor‐9βH‐pimara‐7,19‐diene
Authors: Sicherer‐Roetman Annemarie , Jansen Ben J. M. , de Groot Aede 
Published: September 2010

AbstractThe stereoselective synthesis of (±)‐4,4‐dinor‐9βH‐pimara‐7,19‐diene, 6, is described. This compound represents the B,C‐ring system of the momilactones, fungitoxic diterpenes having a 9βH‐pimarane skeleton. The trans‐syn‐cis tricyclic system was formed via a Diels‐Alder reaction of formyl enone 9 with 2‐(tert‐butyldimethylsilyloxy)‐3‐methyl‐1,3‐butadiene. The resulting regiospecific silyl enol ether was deformylated and stereoselectively reduced to alcohol 26. This alcohol was dehydrated to alkene 22 and acylated to acetate 23, respectively. Alkylation of 22 gave the α‐dithiolanyl compound 27. Alkylation of 23 gave the β‐dithiolanyl compound 35. Compound 27, containing an α‐oriented dithiolanyl group, could be converted into model compound 6, which possesses a β‐oriented vinyl substituent as a result of an equilibrium during the Wittig reaction. Compound 35 was converted into model compound 6 in a straightforward series of transformations.
Electrochemistry of the 9‐phenyl‐10‐methyl‐acridan/acridinium redox system; a high‐potential NADH/NAD+ analogue
Authors: Koper N. W. , Jonker S. A. , Verhoeven J. W. , van Dijk C. 
Published: September 2010

AbstractCyclic voltammetry and preparative controlled potential electrolysis show that the 9‐phenyl‐10‐methyl‐acridinium/acridan (AcPh+/AcPhH) redox couple can be cycled electrochemically between the oxidized (AcPh+) and reduced states (AcPhH) without any apparent side‐reaction. The 9‐phenyl‐10‐methyl‐acridanyl radical (AcPh•) was identified as a first intermediate in the electrochemical reduction of AcPh+ by cyclic voltammetry as well as by electronic absorption and ESR spectroscopy. In contrast to other acridanyl and related dihydropyridyl radicals, AcPh• shows no tendency to undergo dimerization. In aprotic media, AcPh• is shown to undergo a second reversible one‐electron reduction to yield AcPh−, which is, even in these media readily protonated to give AcPhH. The stability of these intermediates seems to be the major factor responsible for the clean electrochemical interconversion of the AcPh+/AcPhH redox couple. The implementation of this redox couple as part of photo‐electrochemical energy conversion systems is discussed.
Potential‐controlled catalytic hydrogenation. Effect of palladium catalyst potential on the selectivity of hydrogenation of polyunsaturated fatty acid esters
Authors: Fröling A. , Hornung F. , de Jongh R. O. 
Published: September 2010

AbstractHydrogenation of methyl linoleate on palladium catalysts in solution with tetraalkylammonium perchlorate as electrolyte, leads mainly to the saturated product methyl stearate. At negative potentials of the catalyst electrode controlled at about − 1 Volt versus a saturated calomel electrode (SCE) with negligible current passage, the monoenic intermediate is the end product, with the double bond found mainly in the Z configuration at the starting 9‐ and 12‐positions. As expected it was found that methyl oleate was not hydrogenated by the catalyst held at − 1.1 Volt, while smooth hydrogenation occurs under identical conditions when the catalyst potential is not controlled. Methyl linolenate leads mainly to dienoic esters at − 1.8 V catalyst potential. The effect was applied on a synthetic scale in the hydrogenation of soya bean oil with palladium catalysts, resulting in a considerable increase of selectivity at negative catalyst potentials.
Analysis of multinuclear lanthanide induced shifts. 3. The structure of 1:3 lanthanide (III)‐glycolate complexes in aqueous solution
Authors: Nieuwenhuizen M. S. , Peters J. A. , Kieboom A. P. G. , Raber D. J. 
Published: September 2010

AbstractLanthanide induced shifts for the 17O, 13C and 1H nuclei of an aqueous solution of glycolate show that the Ln(glycolate)3(D2O)3 complex contains 9 coordinating oxygens situated on a distorted tricapped trigonal prism. The three capping positions are occupied by carboxylate oxygens, the prismatic triangles by either D2O or α‐OH.
Pentacoordinated phosphorus as the internucleoside linkage. Synthesis and 31P NMR study of the pseudorotational dynamics
Authors: Koole Leo H. , Moody Harold M. , Buck Herik M. 
Published: September 2010

AbstractThe synthesis of the first dinucleotide with a pentacoordinated phosphorus as the internucleoside linkage is described. 31P‐NMR measurements revealed that the phosphorus pseudorotation proceeds with rapid stereomutation.
Propellanes. Part LXXXIV. Reduction of [20.3.3]propellane‐24,27‐dione: The three isomeric [20.3.3]propellane‐24,27‐diols
Authors: Ashkenazi Pnina , Weinberg Olga , Zlota Andrei , Ginsburg David 
Published: September 2010

AbstractReduction of [20.3.3]propellane‐24,27‐dione afforded only two of the three expected diols.
I. Photochemical nitration of methoxybenzenes from charge‐transfer complexes with tetranitromethane
Authors: Sankararaman S. , Kochi J. K. 
Published: September 2010

AbstractThe direct irradiation of the charge‐transfer (CT) absorption band of the 1/1 electron donor‐acceptor complexes of dimethoxybenzenes with tetranitromethane leads to aromatic nitration with a high quantum yield. The analogous methoxytoluenes under the same photochemical conditions are converted in equally high yields to products of aromatic trinitromethylation. This dichotomy with different methoxybenzenes (ArH) is discussed within the context of the common reactive intermediates derived from the CT excitation of the complex. The subsequent interactions of the geminate fragments, i.e., \documentclass{article}\usepackage{amsmath}\pagestyle{empty}\begin{document}$[{\rm ArH}^{\underset{{{\scriptscriptstyle\cdot}}}{+}}, {\rm C}({\rm NO}_2)_3 ^ -,\, {\rm \dot NO}_2] $ \end{document} by radical and ion‐pair annihilation represent a unifying mechanism for the CT photochemistry leading to aromatic nitration and trinitromethylation.
Solvent polarity and solvation effects in highly aqueous mixed solvents. Application of the Dimroth‐Reichardt ET(30) parameter
Authors: Haak Jan R. , Engberts Jan B. F. N. 
Published: September 2010

AbstractThe Dimroth‐Reichardt solvent parameter ET(30) and its temperature dependence (25‐50°C) have been measured in water‐rich mixtures of water with acetonitrile (MeCN), 1,4‐dioxane (1,4‐D), dimethyl sulfoxide (DMSO), tert‐butanol (TBA) and 2‐n‐butoxyethanol (2‐BE). Thermodynamically nonideal behavior of the solutions is indicative for preferential solvation of the probe molecule by all organic cosolvents used. However, the effects are most pronounced for TBA and 2‐BE. This leads to ambiguities in the use of the ET(30) value as an indicator of “solvent polarity” for these aqueous binary mixtures. The temperature dependence of ET(30) in TBA‐H2O and 2‐BE‐H2O above the critical hydrophobic interaction concentration is interpreted in terms of binding of the probe to small, temperature‐sensitive aggregates of the cosolvent.
Synthesis and 119Sn NMR of η1‐O‐coordinated sulphine‐dimethyltin dichloride complexes and thermal CS and SO bond cleavage reactions: X‐Ray structure (130 K) of Me2SnCl2[η‐O‐(Me(Ph)NC(Ph)SO)]
Authors: Jans Robert J. F. , van Koten Gerard , Andréa Ronald R. , Vrieze Kees , Spek Anthony L. , Kojić‐Prodić Biserka , de Boer Jan L. 
Published: September 2010

AbstractAminosulphines (R1R2N)(R3)CSO coordinate via the oxygen atom to dimethyltin dichloride. This η1‐O coordination was established by the X‐ray structure of Me2SnCl2[η1‐O‐(Me(Ph)NC(Ph)SO)] which consists of monomers connected to dimers with unequal Sn‐Cl bridges of 2.544(1) and 3.307(1) Å. The tin centres have a distorted octahedral arrangement. The Sn‐O distance is 2.269(3) Å and the Sn‐O‐S angle is 129.1(2)°.Theoretical calculations showed that the negative charge on the sulphine oxygen atom is enhanced by conjugation of the πCS bond with the amino lone pair of the NR1R2 group. Of the other sulphines tested, only 9‐fluorenethione S‐oxide was found to coordinate to Me2SnCl2, likewise in the η1‐O coordination mode. The η1‐O coordination to tin destabilizes the sulphine fragment as was shown by the stoichiometric decomposition of the sulphine into the corresponding ketones and thioketones. A possible route for the decomposition process is proposed involving the formation of an oxathiiran intermediate.
Synthesis of the optical antipodes of 4‐alkyl‐γ‐lactones
Authors: Thijs Lambertus , Waanders Peter P. , Stokkingreef Edwin H. M. , Zwanenburg Binne 
Published: September 2010

AbstractOptical antipodes of 4‐alkyl‐γ‐lactones 3 have been prepared by photochemical rearrangement of optically active α,β‐epoxy diazomethyl ketones 1 in ethanol to give 4‐hydroxy‐alkenoates 2, followed by reduction of the alkene bond and subsequent lactonization. The required epoxy diazomethyl ketones 1 were obtained via the following sequence of reactions: alkylation of 2‐propyn‐l‐ol, subsequent reduction to the alkenols 6, Sharpless epoxidation to 2,3‐epoxy alcohols 7, oxidation to glycidic esters 8 and finally conversion to diazo ketones 1. The enantiomeric purities range from 84 to 100%.
Reactions of enamines of cyclodecanone and cyclododecanone with dimethyl acetylenedicarboxylate in apolar and in polar solvents
Authors: Vos G. J. M. , Benders P. H. , Egberink R. J. M. , Reinhoudt D. N. , Harkema S. , van Hummel G. J. , van der Weerdt A. J. A. 
Published: September 2010

AbstractEnamines of cyclodecanone and cyclododecanone (1a‐d) react with dimethyl acetylenedicarboxylate (DMAD) in an apolar solvent via (2 + 2) cycloaddition and conrotatory opening of the cyclobutene ring in 3 to give the cis,trans‐cycloalkadienes 5a‐d in yields of 44–85%. The compounds 5 do not undergo further thermal or photochemical transformation of the cis,trans moiety. In methanol, the enamines react with DMAD to give bicyclo[7.2.1]dodecene (8a) or bicyclo[9.2.1]tetradecene (8b and 8c) derivatives. These reactions take place via intramolecular nucleophilic addition of the enamine moiety to the α‐methoxycarbonyl group in 10, which is formed from the intermediate Michael adduct 9. The structure of 8b was determined by single‐crystal X‐ray analysis.
Some reactions of an o‐quinone monoimide with derivatives of furan and styrene
Authors: Heine Harold W. , Williams Elizabeth A. 
Published: September 2010

AbstractDiels‐Alder‐type cycloaddition reactions occur across the heterodiene system of the o‐quinone monoimide 1 when 1 is treated with the furans visnagin and 8‐methoxypsoralen. Derivatives of a new heterocyclic system are formed. Similar cycloadditions take place between the heterodiene moiety of 1 and the olefinic linkages present in 7‐methoxy‐2,4‐dimethyl‐3‐chromene (precocene I) and indene. In the former case another ring system previously uncharacterized was produced. Precocene I also reacted with o‐chloranil and an o‐quinone diimide to yield a benzopyrano[3,4‐b] [1,4]benzodioxin and a benzopyrano[3,4‐b]quinoxaline respectively.
Characteristic odoriferous compounds of brown algae: Syntheses of possible oxidation products of (6Z, 9Z, 12Z, 15Z)‐1,6,9,12,15‐heneicosapentaene and (6Z, 9Z, 12Z, 15Z, 18Z)‐1,6,9,12,15,18‐heneicosahexaene
Authors: Broekhof Nico L. J. M. , Witteveen Jan G. , van der Weerdt Anton J. A. 
Published: September 2010

AbstractThe unsaturated aldehydes (3Z, 6Z)‐3,6,11‐dodecatrienal (9), (2E, 4Z, 7Z)‐2,4,7,12‐tridecatetraenal (10) and (3Z, 6Z, 9Z)‐3,6,9,14‐pentadecatetraenal (11) are expected to be products of the air oxidation of heneicosapentaene 1 and heneicosahexaene 2.The first attempts to synthesize aldehydes 9 and 11 (which failed) were based upon repeated Horner‐Wittig reactions with phosphine oxide 12. In a second attempt, acetylene chemistry was applied to prepare aldehydes 9, 10 and 11. Their olfactive properties are described.
Thermolysis of vinyl chloride in nitrogen; rates and products between 601‐681°C
Authors: Manion Jeffrey A. , Louw Robert 
Published: September 2010

AbstractIn a 10‐15‐fold excess of nitrogen, at normal pressure and with τ ca. 3 s, decomposition of vinyl chloride (VC) sets in at about 550°C. At 680°C about 35% decomposition takes place. Major products in this region are HCl, acetylene, 2‐chlorobutadiene and vinylacetylene (1‐buten‐3‐yne). At higher temperatures formation of tar and soot becomes increasingly important. A reaction mechanism in accord with the experimental facts is proposed and analyzed via thermo‐chemical kinetics. Free‐radical chain processes play a major part, with Cl· atoms as important carriers. H abstraction from VC by Cl· leads to ·CH = CHCl and CH2=CCl radicals, respectively. Their relative rate of formation on a per‐H basis is ca. 1/5 around 620°C. The former lose Cl· to give acetylene. The latter add to VC which leads to 2‐chlorobutadiene irrespective of the site of addition (Scheme 1). Various routes to vinylacetylene are discussed. The formation of other (minor) products such as ethylene and methyl chloride is also rationalized. Added HCl is seen to increase the acetylene/2‐chlorobutadiene product ratio with little effect on the rate of conversion of VC. This is due to reversal of the reaction leading to CH2=CCl radicals, through H‐atom transfer from HCl.
Biomimetic total synthesis of steroids X. Synthesis of 7‐(methoxymethyl)‐ and 7‐(phenylmethoxymethyl)‐19‐norsteroids
Authors: Groen M. B. , Zeelen F. J. 
Published: September 2010

AbstractCationic cyclization of 2‐[6‐(m‐methoxyphenyl)‐5‐(methoxymethyl)‐(E)‐3‐hexenyl]‐3‐ methyl‐2‐cyclopentenol 23a and of the phenylmethoxymethyl analogue 23b has been studied. Although oxygen participation with the cyclization by the ether group is possible, and was observed, cyclization to steroids remains the major pathway.The decreased stereoselectivity, when compared with the cyclization of the 7‐methyl analogues, may be due to the occurrence of boat‐like transition states.
Spectroscopic and photochemical properties of mononitropyrenes
Authors: van den Braken—van Leersum A. M. , Tintel C. , van 't Zelfde M. , Cornelisse J. , Lugtenburg J. 
Published: September 2010

AbstractThe influence of the nitro group on the aromatic π‐system of pyrene has been studied by comparing the spectroscopic and photochemical properties of the three mononitropyrenes. Whereas the UV and mass spectra of 1‐ and 4‐nitropyrene show an interaction normal for nitro‐aromatic compounds, this is not observed for 2‐nitropyrene. The lack of interaction is reflected in a UV spectrum very similar to that of pyrene and a mass spectrum with a very low abundance of M ‐ NO. The photochemical behaviour of the three compounds is governed by the degree of interaction. 1‐Nitropyrene shows the nitro‐nitrite rearrangement leading to 1‐hydroxypyrene (88%) and 1‐hydroxy‐2‐nitropyrene (7%). The photoproducts of 4‐nitropyrene are pyrene (9%) and unstable products which react with the solvent. 2‐Nitropyrene is very stable under photochemical conditions due to lack of interaction. Similarly, the sterically hindered 1‐methyl‐2‐nitropyrene is also very stable towards light. The photochemical nitro‐nitrite rearrangement observed for nitro‐aromatic compounds was found to be governed by electronic effects.
Synthesis of a cell‐wall component of Aspergillus niger containing four β (1‐5)‐interlinked D‐galactofuranosyl residues
Authors: Veeneman G. H. , Hoogerhout P. , Westerduin P. , van Boom J. H. , Notermans S. 
Published: September 2010

AbstractThe derivative 2,3‐di‐O‐benzoyl‐5‐O‐chloroacetyl‐6‐O‐pivaloyl‐β‐D‐galactofuranosyl chloride proved to be very suitable for the introduction, via the Helferich procedure, of three β(1–5) interlinked D‐galactofuranosyl residues and a β‐orientated spacer.