bluuebunny/crossref_metadata_2025 huggingface dataset:
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

Cationic 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.
An improved procedure for the synthesis of sugar chloroacetates and some substitution reactions thereof
Authors: Chittenden Gordon J. F. , Regeling Henk
Published: September 2010

An improved and simplified procedure for the preparation of some sugar chloroacetates is described. Nucleophilic substitution of the chlorine atom in some of the products yields the corresponding α‐substituted acetate esters.
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

The 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

The 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.
Stereoselective addition of benzophenone to (C5Me5) Hf (2, 3‐dimethyl‐1, 3‐butadiene)Cl
Authors: Ausema Johannes B. , Hessen Bart , Teuben Jan H.
Published: September 2010

The reaction of (C5Me5) Hf (s‐cis‐C6H10)Cl with benzophenone results in sequential insertion of two ketone molecules in the Hf‐diene bond through adduct intermediates. The final 1,3‐dioxa‐2‐hafnacyclonon‐6‐ene has a cis‐configuration around the double bond, in contrast with related products from (C5H5)2 Zr (diene).
Studies on Borate Esters, Part VII Borate esters of some 1,3‐diones
Authors: van Duin M. , Peters J. A. , Sinnema A. , Kieboom A. P. G. , van Bekkum H.
Published: September 2010

An NMR study of 1,3‐dione‐boric acid systems in DMSO is presented. Formation of borate diesters is preferred over that of borate monoesters. The 1,3‐dione moiety of the borate diester closely resembles that of the free enol tautomer. Addition of proton acids favours borate ester formation.
Electrical conductivity in hexaalkoxytriphenylenes
Authors: van Keulen J. , Warmerdam T. W. , Nolte R. J. M. , Drenth W.
Published: September 2010

Triphenylenes containing six side‐chains O(CH2)nCH3, n  3‐5, have been prepared and doped with iodine. The compounds show mesophases which have been characterised by differential‐scanning calorimetry and small‐angle X‐ray scattering. Samples doped with iodine show an electrical conductivity of 10−4‐10−3Ω−1·m−1, which is slightly higher in the columnar mesophase than in the other phases.
Novel ringtransformations of pyrimidines and pyridines by intramolecular inverse electron demand Diels‐Alder reactions
Authors: Frissen A. E. , Marcelis A. T. M. , Geurtsen G. , de Bie D. A. , van der Plas H. C.
Published: September 2010

2‐(1,1‐Dicyanopent‐4‐yn‐1‐yl)pyrimidines (1) and 2‐(1,1‐dicyanopent‐4‐yn‐1‐yl)nitropyridines (4) undergo intramolecular inverse electron demand Diels‐Alder cycloaddition across the C2‐C5 positions; these adducts lose hydrogen cyanide instantaneously, yielding 7,7‐dicyano‐6,7‐dihydro‐5H‐1‐pyrindines (3) and 1,1‐dicyano‐2,3‐dihydronitroindenes (6), respectively. The intramolecular cyclo‐additions of the pyridine derivatives represent the first examples of inverse electron demand reactions in pyridines.
The chemistry of small‐ring compounds. Part 51. Electron‐transfer‐initiated oxidation of some cyclopropylidene compounds
Authors: Hofland A. , de Boer Th. J.
Published: September 2010

Cyclopropylidene compounds of type 1 are found to quench the fluorescence of 9,10‐dicyanoanthracene (DCA). Nevertheless photo‐oxygenation, in the presence of DCA, leads under no circumstances to dioxetanes but (in ethanol) to a methoxy hydroperoxide 5, as tentatively shown in Scheme 2. This hydroperoxide undergoes acid rearrangement either to a lactone or to a cyclobutanone, depending on the reaction conditions (Scheme 3).
Synthesis, purification and spectral analysis of mononitrocyclopenta[cd]pyrenes
Authors: van den Braken‐van Leersum A. M. , Spijker N. M. , Lugtenburg J. , Cornelisse J.
Published: September 2010

The synthesis, purification and characterization of seven isomeric nitrocyclopenta[cd]‐pyrenes (nitroCPPs) are described. Nitration of partially hydrogenated CPPs affords mixtures of nitro derivatives, which, after separation, are aromatized with DDQ. The resulting nitroCPPs are characterized by their 1H NMR, 13C NMR, UV‐vis, IR and mass spectra. The interaction between the nitro group and the aromatic system of CPP is discussed.
Synthesis of phosphopeptides: A simple phosphorylation procedure for serine and threonine
Authors: de Bont H. B. A. , Veeneman G. H. , van Boom J. H. , Liskamp R. M. J.
Published: September 2010

Treatment of suitably protected serine and threonine derivatives with N,N‐diethylaminodibenzylphosphoramidite, followed by subsequent treatment with tert‐butyl hydroperoxide affords the phosphorylated amino acids in good yields. After deprotection and coupling with the hydroxybenzotriazole ester from Boc‐Ala the protected phosphopeptides are obtained in good yields.
Reactivity of pyrene dianion and some of its 2‐substituted derivatives
Authors: Rodenburg L. , de Block R. , Bieze T. W. N. , Cornelisse J. , Lugtenburg J.
Published: September 2010

A simple technique for the preparation of anions of polycyclic aromatic hydrocarbons is described. 1H and 13C NMR spectra of dianions of pyrene and derivatives of pyrene are reported and discussed. The electron density is greatest at the carbon atoms in the perimeter of the dianions. The presence of an electron‐donating substituent at position 2 causes an increase in the charge at positions 1 and 3.
An improved synthesis of tetraarylporphyrins
Authors: van der Made A. W. , Hoppenbrouwer E. J. H. , Nolte R. J. M. , Drenth W.
Published: September 2010

An improved synthesis for 5,10,15,20‐tetrakis(pentafluorophenyl)porphyrin, 5,10,15,20–tetrakis(2,4,6‐trimethylphenyl)porphyrin and 5,10,15,20‐tetrakis(2,6‐dichlorophenyl)porphyrin by an acid‐catalysed condensation of pyrrole and properly substituted aldehyde, followed by oxidation, is reported, with yields of up to 30% being obtained.
An ESR spin‐probe study of didodecyldimethylammonium bromide vesicles
Authors: Buhre Louise M. D. , Rupert Leo A. M. , Engberts Jan B. F. N.
Published: September 2010

The ESR spin‐probe technique has been used to investigate structural changes in didodecyldimethylammonium bromide (DDAB) bilayer vesicles (average diameter of 2000 and 3000 Å, respectively) around the phase transition temperature and in the presence of a fusogenic agent. Among several popular nitroxide spin‐probes, TEMPON‐DNPH is the only probe which binds effectively to the DDAB vesicles. Analysis of nitrogen hyperfine splitting constants (AN) revealed two different binding sites for TEMPON‐DNPH. At binding site I, the spin‐probe floats on the bilayer surface. At binding site II, the nitroxide moiety penetrates into the bilayer and experiences a more apolar microenvironment. The temperature dependence of AN indicates an increase in micropolarity at binding site II during the phase transition from a gel‐like to a liquid‐crystalline state of the bilayer. This effect is more pronounced for the larger vesicles. Estimates of the effective rotational correlation times suggest that the molecular tumbling of the probe increases with increasing temperature. No ESR spectral evidence was obtained for structural alterations in the vesicle bilayer under conditions of aggregation or fusion. This result is rationalized by assuming that binding site II is located too deeply in the vesicle bilayer to be affected by changes at the bilayer surface as they occur upon interaction with the fusogenic agent.
5‐Demethylretinal and its 5‐2H, 7‐2H2 and 5,7‐2H2 isotopomers. Synthesis, photochemistry and spectroscopy
Authors: Spijker‐Assink M. B. , Winkel C. , Baldwin G. S. , Lugtenburg J.
Published: September 2010

All‐trans‐5‐demethylretinal and its 5‐2H, 7‐2H and 5,7‐2H2 isotopomers have been synthesized by means of a new and simple scheme. Using photochemistry, the 9‐, 11‐ and 13‐cis, as well as the 9,13‐ and 11,13‐di‐cis isomers, were obtained. The structures were established by means of 1H NMR spectroscopy.
Halogénocyclogermazanes: Influence des substituants halogènes sur l'existence d'un équilibre cyclogermazane⇄germa‐imine
Authors: Rivière‐Baudet M. , Khallaayoun A. , Satgé J.
Published: September 2010

Studies of ring opening of chlorocyclotrigermazanes in cycloaddition reactions with the nitrones phenyl‐ and tert‐butylbenzylideneamine N‐oxide, catalysed by Lewis bases (HMPA) or Lewis acids (ZnCl2; M(CO)6; M(CO)5·THF, M = Cr, W), show that hexachlorocyclotrigermazanes are much less reactive than the corresponding methylcyclogermazane. The decreased reactivity is attributed to the tendency of the electron‐attracting chlorine atoms to promote the “back‐donation” of electrons from nitrogen to germanium, thereby rendering the Ge‐N bond less polar and therefore less susceptible to coordination (either with Lewis acids or Lewis bases) and attack by polar reagents such as carbonyl compounds.
The formation of 1,3‐di‐Grignard reagents from small‐ring 1,3‐dibromides
Authors: Seetz J. W. F. L. , Ent H. , Rookhuizen R. Boer , Akkerman O. S. , Bickelhaupt F.
Published: September 2010

The reaction of 1,3‐dibromocyclobutane (5) and of 1,3‐dibromocyclopentane (6) with magnesium in diethyl ether has been investigated. The corresponding 1,3‐di‐Grignard reagents7(<9%) and12(〉〉45%), respectively, were obtained. Compound12decomposes to (2‐cyclopentenyl)magnesium bromide (13) with a half‐life of 5 h. The yields and stabilities of7and12are briefly discussed.
The structure of 1,1‐dichloro‐1‐methyl‐1λ5‐stibacyclopentane
Authors: Meinema H. A. , Noltes J. G. , Spek A. L. , Duisenberg A. J. M.
Published: September 2010

Crystals of 1,1‐dichloro‐1‐methyl‐1λ5‐stibacyclopentane are tetragonal, space group I***4, with a = b = 15.645(7), c = 7.103(7) Å. The structure was solved using standard Patterson and Fourier methods and refined by full‐matrix least‐squares techniques to a final R = 0.047 for 841 observed reflections. The crystal structure contains tetrameric clusters of 1,1‐dichloro‐1‐methyl‐1λ5‐stibacyclopentane with short (3.613(6) Å) intermolecular Sb…Cl contacts. The coordination geometry about Sb is found to be significantly distorted from the trigonal bipyramidal 5‐coordination, observed in non‐cyclic dichlorotriorganoantimony(V) compounds, R3SbCl2, into the direction of octahedral 6‐coordination. The five‐membered C4Sb ring has a twisted conformation with a CH2‐Sb‐CH2 bond angle of 90.4(8)°.
Synthesis and characterization of novel tri‐ and tetra metallic isopropoxides of later “3d” metals
Authors: Dubey R. K. , Shah A. , Singh A. , Mehrotra R. C.
Published: September 2010

A novel series of monomeric and generally volatile polymetallic isopropoxides of the types [Al(O‐i‐Pr)4]M[Ga(O‐i‐Pr)4], [M'(O‐i‐Pr)4]M[Zr2(O‐i‐Pr)9], [M”(O‐i‐Pr)6]M[Zr2(O‐i‐Pr)9], [M'(O‐i‐Pr)4]M[M”(O‐i‐pr)6], [Al(O‐i‐Pr)4]Fe[Zr2(O‐i‐Pr)9], [[Al(O‐i‐Pr)4]Fe[Zr2(O‐i‐Pr)9]2], [FeCl[Al(O‐i‐Pr)4][Zr2(O‐i‐Pr)9]] and [Fe[Al(O‐i‐Pr)4][Zr2(O‐i‐Pr)9][M”(O‐i‐Pr)6]] [where M = Mn(II), Fe(II), Co(II), Ni(II); M' = Al(III) or Ga(III); M” = Nb(V) or Ta(V)] has been synthesized by the reaction of bi‐ or tri‐metallic chloride isopropoxides with a potassium isopropoxy‐metallate derivative in an appropriate molar ratio. All these complexes have been characterized by elemental analysis, spectroscopic, magnetic and molecular weight measurements.
Less common modes of coordination in α,ω‐bis(di‐tert‐butylphosphino)alkane and α,ω‐bis(di‐tert‐butylphosphino) (poly)ether complexes of rhodium(I)
Authors: Timmer Klaas , Thewissen D. Harry M. W. , Marsman Jan W.
Published: September 2010

α,ω‐Bis(di‐tert‐butylphosphino)alkane and α,ω‐bis(di‐tert‐butylphosphino) (poly)ether ligands are prepared in appreciable yields via reaction of the appropriate dihalide with two equivalents of Lip‐t‐Bu2. Reaction of [Rh(COD)(acetone)2][OTf] with the former ligands yields bridged complexes of the type [Rh(COD)(OTf)]2[μ‐t‐Bu2P(CH2)n,P‐t‐Bu2] (n = 5 and 8), containing coordinated triflate. With the ligand t‐Bu2PCH2CH2OCH2CH2P‐t‐Bu2 the monomeric complex [Rh(COD)(P∩P)][OTf] is isolated, in which the diphosphine ligand is coordinated through oxygen and one phosphorus atom. In the case of the ligand t‐Bu2P(CH2CH2O)2CH2CH2P‐t‐Bu2, the bridged complex [[Rh2(COD)2(OTf)](μ‐P∩P)][OTf] is formed, containing both coordinating and non‐coordinating triflate. In solution this complex rearranges to [[Rh(COD)]2(μ‐P∩P)][OTf]2, in which the ligand is coordinated to both rhodium nuclei via one phosphorus and one oxygen atom. With Cl−, CO and SO2, [Rh(COD)(t‐Bu2PCH2CH2OCH2CH2P‐t‐Bu2)][OTf] reacts to [Rh(COD)(Cl)]2‐(μ‐P∩P), [Rh(CO)(P∩P)][OTf] and [Rh(SO2)(P∩P)][OTf], respectively. In the reaction of [Rh(COD)(OTf)]2[μ‐t‐Bu2P(CH2),P‐t‐Bu2] with CO2 one of the reaction products is most probably [Rh(CO)3(P∩P)][OTf] with cis‐coordinated diphosphine. [Rh(COD)(Cl)]2(μ‐t–Bu2PCH2CH2OCH2CH2P‐t‐Bu2) reacts with CO to [Rh(CO)(P∩P)][Rh(CO)2(Cl)2].
Ab initio calculation on oxomanganese porphine chloride; relevance to its oxidizing capacity
Authors: den Boer D. H. W. , van Lenthe J. H. , van der Made A. W.
Published: September 2010

The minimal basis‐set gradient‐SCF calculations on the title molecule are reported with a view to elucidating its electronic structure and contributing towards a better understanding of its catalytic capacity in epoxidation reactions. It has been found, within C4v symmetry, that the oxygen is predominantly π‐bonded to the metal atom in a closed‐shell spin state of the complex. The availability of low‐lying unoccupied Mn d π‐O pπ molecular orbitals provides a plausible explanation for the oxygen insertion in epoxidation reactions.
Vapour‐pressure measurements and thermodynamic properties; 1,3,5‐tribromobenzene
Authors: Huinink J. , van Miltenburg J. C. , Oonk H. A. J. , Schuijff A.
Published: September 2010

This paper deals with the techniques in use by our group for the experimental determination of vapour pressures. We report the vapour pressures for 1,3,5‐tribromobenzene between 295 and 389 K (solid) and between 397 and 410 K (liquid). The enthalpies of sublimation and vaporization are derived from the dependence of vapour pressures on temperature: ΔH°SUB(334.78 K) = 83.54 ± 2 kJ/mol, ΔH°vap(403.23 K) = 58.68 ± 1.5 kJ/mol.
Synthesis, X ‐ ray crystal structure and reactions of dimethyl(N,N,N′,N′‐ tetramethylethanediamine)palladium
Authors: de Graaf Wim , Boersma Jaap , Grove David , Spek Anthony L. , van Koten Gerard
Published: September 2010

The title compound has been synthesized and characterized by X‐ ray crystallography. Thermolysis in benzene at 80°C affords a 3: 1 mixture of methane and ethane, whereas reaction with benzyl bromide affords solely ethane and [Pd(CH2Ph)(Br)(Me2NCH2CH2NMe2)]; other preparatively useful reactions are described.
Reactions of 11C recoil atoms with benzene. I. Formation of 11C labelled benzaldehyde
Authors: Kuipers P. , van Halteren B. W. , Leurs G. A. J. , Lindner L. , Brinkman G. A.
Published: September 2010

Reactions of 11C recoil atoms with C6H6 in the presence of O2 lead to the formation of high yields of labelled C6H5CHO in the gaseous (6%) and liquid (8‐10%) phase, whereas none was detected in the solid phase. For the liquid phase, 63% of the 11C activity in C6H5CHO is in the ‐CHO group, while 37% is part of the aromatic ring; in the case of gaseous C6H6 with 37% O2, the amount of 11C in the ring is only 11%. The reactions possibly leading to the formation of [11C]C6H5CHO and the 11C distribution over the molecule are discussed.
Synthesis of a trisaccharide‐ribitol‐phosphate analogue of the repeating unit of the complex polysaccharide, C‐substance, from Streptococcus pneumoniae type 1
Authors: Hermans J.P.G. , Noort D. , van der Marel G.A. , Hoogerhout P. , van Boom J.H.
Published: September 2010

The synthesis of analogue 14f (Scheme 2) of a fragment of the S. pneumoniae type 1 C‐substance antigen (Fig. 1, Ia) is presented. The protected disaccharide 5 and trisaccharide 7 (Scheme 1) were prepared by silver trifluoromethanesulfonate‐catalyzed α‐glycosylation of 2c with 4b (54%) and 2d with 6b (59%), respectively. A silver‐silicate‐catalyzed β‐glycosylation of ribitol derivative 9 with trisaccharide bromide 8b gave 10a (55%). The selectively deprotected trisaccharideribitol 10b was coupled with spacer 11 (Scheme 2) using phosphorylating reagent 12 to give the fully protected phosphotriester derivative 14a (98%). The stepwise deprotection of 14a, including conversion of the azide functions into acetamido groups, turned out to be troublesome and afforded 14f in low yield.
Preparation of 1,6‐anhydroglucose from (1→4)‐glucans using microwave technology
Authors: Straathof Adrie J. J. , van Bekkum Herman , Kieboom Antonius P. G.
Published: September 2010

Heating of starch or other (1→4)‐glucans in a conventional microwave oven yields 1,6‐anhydro‐β‐D‐glucopyranose within a few minutes. Preparation of small amounts of this compound is rapid and easy by this method.
Lariat formation in splicing of pre‐messenger RNA. Conformation and base stacking at the lariat branch point studied using 500‐MHz 1H NMR and CD spectroscopy
Authors: Koole Leo H. , Buck Henk M. , Kuijpers Will H. A. , Balgobin Neil , Nyilas Agnes , Remaud Gerald , Vial Jean‐Marc , Chattopadhyaya Jyoti
Published: September 2010

A conformational‐analysis study based on 500‐MHz 1H NMR and circular dichroism (CD) has been performed on the branched trinucleotide U‐5′‐3′‐A‐2′‐5′‐G (1) which models the branch point in the lariat structure of Group‐II excised introns. The NMR and CD results are in agreement with previous work in which it was shown that adenine 2′‐5′ guanine base stacking essentially determines the molecular conformation of compound 1. The ribose ring of the A residue shows a preference for the S conformation, while the riboses of U and G are highly flexible, i.e. no clear preference for N or S is observed. CD spectroscopy of 1 showed that ethylene glycol leads to disruption of adenine 2′‐5′ guanine stacking. Furthermore, we studied the unnatural branched trinucleotide G‐5′‐3′‐A‐2′‐5′‐U (2) in which U and G are reversed in comparison with compound 1. The molecular conformation of 2 is far more rigid in comparison with 1, as a result of very strong adenine 2′‐5′ uracil stacking. Ethylene glycol was apparently unable to facilitate de‐stacking of adenine and uracil in 2. The present results show that guanosine as the 2′linked nucleotide corresponds with a clear molecular flexibility. This may be of relevance in understanding why guanosine, as the 2′‐5′ nucleotide, is a prerequisite for the occurrence of the second step in group‐II splicing.
All E‐10,20‐methanoretinoylopsin, light‐stable rhodopsin. Synthesis and spectroscopy of all E‐10,20‐methano‐ and all‐E‐retinoyl fluoride and their reaction with bovine opsin
Authors: van der Steen R. , Groesbeek M. , van Amsterdam L. J. P. , Lugtenburg J. , van Oostrum J. , de Grip W. J.
Published: September 2010

In order to obtain a light‐stable rhodopsin as a potential candidate for crystallization and structural X‐ray analysis, we synthesized and characterized the novel all E‐10,20‐methano‐retinoyl fluoride (2). This retinal analogue has a locked 11‐cis configuration, preventing the light‐induced 11‐cis → trans isomerization and binds to opsin by a stable peptide bond rather than a Schiff base. 2 reacted with (methylated) bovine opsin, forming a light‐ and thermo‐stable pigment with λmax at 390 nm. Its opsin shift (2500 cm−1) is in the same order of magnitude as that in rhodopsin (2650 cm−1), suggesting that the mechanism for the red shift is not located in the direct vicinity of the chromophore‐protein linkage. We also report the first synthesis and characterization of all‐E‐retinoyl fluoride (10), which failed to give a pigment on reaction with bovine opsin.
Partition coefficients of crown ethers
Authors: Stolwijk Theodoras B. , Vos Lambertus C. , Sudholter Ernst J. R. , Reinhoudt David N.
Published: September 2010

Benzo and dibenzo crown ethers become more water soluble as the number of oxyethylene units increase. Moreover, the solubility in water is larger than expected on the basis of calculations using empirical models, viz., “the fragment model” and “the substituent model”. New hydrophobic fragmental constants of the oxyethylene fragment, f (‐OCH2CH2‐) = −0.17, and of the veratrole fragment, f[C6H4(OCH2‐)2] = 0.99, for the system 1‐octanol/water have been determined experimentally. Using these values, reliable partition coefficients of macrocyclic polyethers can be calculated. Comparison of the benzo crown ethers with the open‐chain model compounds surprisingly did not reveal a macrocyclic effect on the partition coefficient.
Diene systems in N‐formylmorphinans; formation of a dibenz[d,f]azonine: A new example of molecular acrobatics in morphinans1 (chemistry of opium alkaloids, part XXVII)
Authors: Linders J. T. M. , Booth R. J. , Lie T. S. , Kieboom A. P. G. , Maat L.
Published: September 2010

A new synthesis of 6‐demethoxy‐N‐formyl‐N‐northebaine (1) and its spectacular rearrangement to dibenzazonine 8 are described.

N‐Demethylation of codeine (2) gave N‐norcodeine (3) which was converted into the mesyl compound 5 by N‐formylation with ethyl formate, followed by reaction with mesyl chloride in pyridine. A short treatment of 5 with lithium bromide afforded 7 which, upon reaction with potassium tert‐butoxide, yielded 1. Reaction of 7 with zinc in ethanol gave morphinan‐5,7‐diene 9. Prolonged treatment of morphinan 5 with lithium bromide gave dibenzazonine 8, which could also be obtained by reaction of 1 with hydrogen bromide. A mechanism for this rearrangement is proposed.

The 1H and 13C NMR spectra of the new compounds are discussed.
Synthesis of cyclogentiotriose and cyclogentiotetrose peracetates
Authors: Bonas Georges , Excoffier Gerard , Paillet Michel , Vignon Michel
Published: September 2010

The syntheses of cyclogentiotriose and cyclogentiotetrose peracetates by intramolecular cyclization of corresponding linear activated oligosaccharides are described.

The optimization of cyclization of linear glucotetrose has been performed according to two different routes, (a) and (b). Route (b), which corresponds to activation of the anomeric carbon with dichloromethyl methyl ether/boron trifluoride etherate reagent, prior to removal of the O‐6 trichloroacetyl ester group with ammonia, proved to be superior, in terms of yield, to route (a).
The use of zeolites in organic reactions
Authors: van Bekkum H. , Kouwenhoven H. W.
Published: September 2010

The use of zeolites as selective catalysts and adsorbents in organic syntheses is a field of growing importance. A brief discussion of the structure, modification and catalytic properties of zeolites relevant to the topic is presented. Some non‐ and semi‐catalytic applications of zeolites in fine‐chemical preparation are mentioned and examples are given of zeolite catalysis in oil refining and petrochemicals production. Further examples of the use of zeolites as catalysts in organic reactions are chosen from the fields of isomerization, aromatic substitution, oxidation, cyclization and heterocyclic ring formation.
Synthesis of indoles and L‐tryptophans specifically 2H‐ or 13C‐labelled in the six‐membered ring
Authors: van den Berg Ellen M. M. , van Liemt Willem B. S. , Heemskerk Bram , Lugtenburg Johan
Published: September 2010

(4‐2H)‐, (5‐2H)‐, (6‐2H)‐, (7‐2H)‐, (4‐13C)‐ and (5‐13C)‐1H‐indole and the corresponding six L‐tryptophans [(4‐2H)‐, (5‐2H)‐, (6‐2H)‐, (7‐2H)‐, (4‐13C)‐ and (5‐13C)‐] have been synthesized from simple labelled starting materials via a single reaction scheme. The L‐tryptophans were prepared from the indoles via a quantitative one‐step biosynthetic conversion. A scheme leading to the synthesis of three other indoles, mono‐13C‐enriched in the six‐membered ring, has been developed and optimized. Indole and L‐tryptophan, 13C‐ or 2H‐enriched at the positions 4 or 5, have been synthesized with 99% isotope incorporation without scrambling. (6‐2H)‐1H‐Indole and ‐tryptophan have been synthesized with 95% deuterium incorporation and (7‐2H)‐1H‐indole and ‐tryptophan with 96%. The reactions have been carried out on a gram scale and, in the case of the 4‐13C system, they have been scaled up to the ten‐gram level with no deterioration in yield.
Sialic acid patterns in N‐linked carbohydrate chains. Structural analysis of the N‐acetyl‐/N‐glycolyl‐neuraminic‐acid‐containing N‐linked carbohydrate chains of bovine fibrinogen
Authors: Damm J. B. L. , Bergwerff A. A. , Hård K. , Kamerling J. P. , Vliegenthart J. F. G.
Published: September 2010

The N‐linked carbohydrate chains of bovine fibrinogen have been released by peptide‐N4‐(N‐acetyl‐β‐glucosaminyl)asparagine amidase‐F, fractionated by FPLC and HPLC procedures and characterized by 500/600‐MHz 1H NMR spectroscopy. Evidence is presented for the native sialic acid patterns, involving the occurrence of α2 → 6‐linked N‐acetyl‐ and N‐glycolylneuraminic acid residues in the terminal position of the di‐antennary carbohydrate chains. Details are included of minor oligosaccharides containing Neu5Acα2 → 3Galβ 1→ 4/β1 → 3GlcNAc β1 → structural elements, which have not been previously described in this glycoprotein.
Biosynthesis of blood‐group‐I and ‐i antigens. A specific assay for a developmentally regulated β6‐N‐acetylglucosaminyltransferase. Application to normal and malignant hematopoietic cells
Authors: Koenderman Anky H. L. , Koppen Piet L. , van den Eijnden Dirk H. , Wijermans Pierre W. , Langenhuijsen Mart M. A. C.
Published: September 2010

A specific assay for the activity of UDP‐GlcNAc: β‐galactoside β6‐N‐acetylglucosaminyltransferase B has been developed. The assay is based on the use of the specific acceptor Galβ1 → 3Galβ1 → 4Glc and the analysis and characterization of the product by HPLC. Using this assay, the role of the transferase in the developmentally regulated expression of the GlcNAcβ1 →3(GlcNAcβ1 → 6)Gal branching points in blood‐group‐I‐active polylactosaminogly‐cans, as well as the Galβ1 → 3(GlcNAcβ1 → 6)GalNAc core‐type‐2 structure of O‐linked carbohydrates, has been investigated in normal and malignant hematopoietic cells. In the erythroid, myeloid and the monocytic system, the activity of the transferase appeared to decrease with differentiation and maturation. This decrease is opposite to that which would be expected on the basis of available structural and immunological data, which suggest that branching of polyactosaminoglycans and/or formation of core‐type‐2‐based O‐linked chains, resulting in the expression of I activity, increase with maturation.

It is possible that more than one β6‐N‐acetylglucosaminyltransferase B activity is implicated in the synthesis of β6‐GlcNAc‐containing structures; the alternative is that the enzyme, assayed with Galβ1 → 3Galβ1 → 4Glc, is involved but that the expression of these structures is also dependent on low activities of competing glycosyltransferases. On the other hand, the synthesis of the branching points in polylactosaminoglycans might proceed through an alternative reaction sequence involving β6‐N‐acetylglucosaminyltransferase A.
Syntheses of tri‐ and tetrasaccharide fragments of the capsular polysaccharide of Streptococcus pneumoniae type 23F
Authors: van Steijn A. M. P. , Jetten M. , Kamerling J. P. , Vliegenthart J. F. G.
Published: September 2010

The syntheses of two trisaccharides, being fragments of the capsular polysaccharide of Streptococcus pneumoniae type 23F (3‐OPO2−3)‐β‐D‐Glcp‐(1‐4)‐[α‐L‐Rhap‐(1‐2)]‐β‐D‐Galp‐(1‐OCH3) (1), α‐L‐Rhap‐(1‐2)‐β‐D‐Galp‐(1‐4)‐β‐L‐Rhap‐(1‐OCH3) (2) and the repeating unit (3‐OPO32−)‐β‐D‐Glcp‐(1‐4)‐[α‐L‐Rhap‐(1‐2)]‐β‐D‐Galp‐(1‐4)‐β‐L‐Rhap‐(1‐OCH3) (3), are presented.
The role of axial chirality in schiff bases of pyridoxal phosphate and amino acids in the mechanism of racemase enzymes. A quantum‐chemical study
Authors: van Genderen Marcel H. P. , Buck Henk M.
Published: September 2010

In the enzymatic racemization of L and D amino acids, the coenzyme pyridoxal phosphate (PLP) forms a Schiff base with the amino acid. In the first step of the isomerization reaction, both the L and D PLP‐amino acid compounds are deprotonated by a single basic site in the enzyme, which is normally assumed to occur via large conformational changes of coenzyme or enzyme. We propose a more efficient mechanism in which axial chirality is introduced into the PLP‐amino acid complex by a rotation around the C4C4′ bond, placing the iminium side‐chain in an out‐of‐plane orientation. This allows optimal location of both L and D amino acids for deprotonation by one basic site in the enzyme. A combination of the calculated results with the kinetic data of Farad and Walsh (Biochemistry 27, 3267 (1988)) provides insight into the location of the catalytic base in the enzyme with respect to the coenzyme.
The weak‐overlap bond: An SGF (Simplified Group Function) analysis
Authors: Schipper Pieter E.
Published: September 2010

Substituent and solvent effects in reactivity and spectroscopy, as well as bonding in Van der Waals and/or hydrogen‐bonded dimers, fall within the weak‐to‐zero‐overlap regime. The simplified group function (SGF) approach coupled with a fixed spin (FS) electronic representation is shown to lead to a systematic theoretical development of the wave function in this bonding region in a manner paralleling intuitive chemical thinking; i.e. in terms of labelled electrons of fixed spin “jumping” between specific‐group orbitals (FS activity). The readily visualizable resolution into types of FS activity is shown to also underlie the formal theoretical resolution of the SGF wave function, and thus any observables derived from it. In particular, the energetics of the weak‐overlap bond (the SGF potential) is developed in the perturbative limit of mixing excitation structures, leading to additive long‐range (overlap independent: static, inductive, dispersive) and short‐range (overlap dependent: dative, codative, covalent and Pauli‐induced) contributions. An important feature of SGF methodology in analytic application to substituent and solvent effects is that simplification of the wave function is achieved through systematic suppression of interchange activity, thereby retaining the full form of the Hamiltonian including, e.g., electron‐electron repulsion). This is demonstrated in a range of applications: viz. (i) to a justification for frontier‐orbital theory and the angular‐overlap model; (ii) to a description of substituent effects in aromatic electrophilic substitution; and (iii) to the development of a simple framework for discussing solvent/ligand effects on solute/metal transition energies.
A kinetic study of the alkaline hydrolysis of four‐coordinated phosphorus (PIV) compounds. Impact of conformational transmission in the transiently formed five‐coordinated (PV‐TBP) intermediates on reaction rate and product distribution
Authors: Koole Leo H. , Olders Edith A. T. A. , Opresnik Marko , Buck Henk M.
Published: September 2010

It can be shown that alkaline hydrolysis of four‐coordinated phosphorus (PIV) compounds is substantially accelerated if the trigonal‐bipyramidal (TBP) five‐coordinated phosphorus (PV) intermediate in the reaction can exhibit conformational transmission. With the compounds 5a‐c, it was shown that this acceleration is an entropy effect. Pseudorotation in the PV‐TBP intermediate is facilitated if conformational transmission occurs, and therefore the entropy loss during build‐up of the PV‐TBP is reduced. This evidently results in a lower free energy of activation for the reaction. For the phosphate triester systems 6a and 6b, it was also found that the occurrence of conformational transmission speeds up the hydrolysis reaction, although the effect is less pronounced than for compounds 5a‐c. The cyclopentylmethoxy group (6a) and the tetrahydrofurfuryloxy group (6b) show slight preferences for equatorial and axial positioning in the transient PV‐TBP, respectively. This study shows for the first time that reaction rate and product selectivity of hydrolyses of phosphate esters can be determined in part by the conformational transmission effect.
Study of propene metathesis on MoO3−x/Al2O3 catalysts; effect of diazomethane decomposition
Authors: Ghazi M. , Sachtler W. M. H.
Published: September 2010

Propene metathesis has been studied at 295 K and 1 atm in He or in H2 with MoO3−x/Al2O3 catalysts which were reduced at 673 K. Some catalysts were modified by exposing them to diazomethane vapor prior to testing. The diazomethane was synthesized shortly before use; it was stored by dissolving its vapor in di‐n‐butyl phthalate. Metathesis of the unmodified catalysts revealed an induction period during which the activity increased; this period is markedly shorter in H2 than in He. In He, metathesis is the sole reaction, in H2 it is accompanied by a prevailing hydrogenolysis. No induction period is visible for catalysts modified with diazomethane in accordance with the assumption that surface carbenes are reaction intermediates. The activity is, however, lowered by this treatment, as catalyst deactivation is enhanced by the pretreatment with diazomethane.
Mechanistic studies of the oxidative‐coupling polymerization of 2,6‐dimethylphenol. Part II. Specificity of the reaction and formation of diphenoquinone
Authors: Viersen F. J. , Challa G. , Reedijk J.
Published: September 2010

Copper‐(N,N,N′,N′‐tetramethylethylenediamine) (tmed) complexes as catalysts in the oxidative‐coupling polymerization of 2,6‐dimethylphenol (DMP) give rise to poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) in high yield, although the formation of the undesired 3,5,3′,5′‐tetramethyldiphenoquinone (DPQ) cannot be completely avoided.

At ligand‐to‐copper ratios lower than 10, the specificity for PPO formation can be raised by increasing the N/Cu ratio and by the addition of a strong base (potassium or lithium hydroxide). However, once a fivefold excess of tmed is used, neither further tmed nor hydroxide addition raises the specificity beyond 97% PPO. Using an N/Cu ratio of 10, neither the catalyst concentration nor the DMP concentration has an effect on the product composition.

On the basis of the experimental results included in this paper, together with those published in the literature, it is concluded that the specificity is not affected by the structure of the copper complex, provided that sufficiently high ligand‐to‐copper ratios are used. This results in a product formation which always consists of ca. 3% of DPQ and 97% PPO. The DPQ is formed mainly during the initial stages of the reaction.

However, final DPQ yields of up to 45 % are found for N/Cu < 4. High concentrations of mononuclear copper species Cu(tmed)22+ appear to be present under these conditions as deduced from EPR experiments (in addition to polynuclear CuxCly species). Based on this observation, a radical mechanism for DPQ formation, using Cu(tmed)22+ as oxidation catalyst, is proposed. There are thus two distinct reaction conditions: (1) At high N/Cu ratios, the highly active dinuclear complex yields 97% polymer and ca. 3% DPQ. In this case, however, factors which would influence the structure or concentration of the catalyst do not appear to affect the specificity. (2) At low N/Cu ratios, the presence of high concentrations of mononuclear Cu(tmed)22+ results in high yields of DPQ and in this case, the hydroxide concentration strongly affects the specificity.
pH‐Dependence in the Cu(I)‐mediated oxidation of toluene with oxygen or hydrogen peroxide
Authors: Okunowski J. K. , van Dam H. E. , van Bekkum H.
Published: September 2010

pH is shown to exert a profound effect on the selectivity of the Cu(I)‐mediated oxidation of toluene with oxygen or hydrogen peroxide. At low pH, methyl‐group oxidation predominates, whereas at pH > 3, ring hydroxylation prevails. A common mechanism for oxygen and hydrogen peroxide oxidation is suggested.
The effect of alloying on the adsorption of nitric oxide on platinum and rhodium (100). A TDS study using a Pt‐Rh(100)‐alloy single‐crystal surface
Authors: Siera J. , van Groos M. J. Koster , Nieuwenhuys B. E.
Published: September 2010

The adsorption and dissociation of NO have been studied on a Pt‐Rh(100)‐alloy single‐crystal surface by thermal‐desorption spectroscopy (TDS). It was found that, at low coverages, NO dissociates completely upon heating to form N2 and O2. At higher coverages, NO desorption was observed, in addition to desorption of N2, and two new N2 desorption peaks appeared. Three N2 desorption peaks were distinguished. The results are compared with literature data concerning NO adsorption on Rh(100) and Pt(100). It is concluded that, at low coverages, the Rh sites are responsible for NO bond scission activity.
The cycloaddition reaction of α‐oxo sulfines and 2‐trimethylsilyloxy‐1,3‐butadienes
Authors: Rewinkel J. B. M. , Zwanenburg B.
Published: September 2010

The cycloaddition reaction of α‐oxo sulfines with 2‐(trimethylsiloxy)‐1,3‐dienes, leading ultimately to thiacyclohexanone S‐oxides (alternatively named as thianone S‐oxides or perhydrothiapyranone S‐oxides) is described. 1‐Oxo‐2‐thioxo‐indane S‐oxide 2a, and several α‐oxo sulfines generated in situ have been studied. The cycloaddition reaction is regioselective, and thiacyclohexan–3‐one S‐oxides are the preponderant or the exclusive products. In the case of 1‐ethoxy‐3‐(tri‐methylsiloxy)‐1,3‐butadiene 3c the primary cycloadduct with sulfine 2a can either undergo mild hydrolysis to give a thiacyclohexan‐3‐one S‐oxide 6h or elimination to give thia‐4‐cyclohexen‐3‐one S‐oxide (2,6‐dihydrothiapyran‐3‐one S‐oxide) 6i. The regiochemistry of these cycloadditions is discussed in terms of HOMO/LUMO coefficients.
Synthesis and transport properties of rigid poly(octasubstituted phthalocyaninatosiloxanes)
Authors: van der Pol J. F. , Zwikker J. W. , Warman J. M. , de Haas M. P.
Published: September 2010

Coaxially polymerized, peripherally substituted derivatives of phthalocyanine (‐[SiPc(CnH2n+ 1)8‐O‐]; n = 8, 12) have been synthesized and characterized. They display efficient energy‐migration properties and a dark conductivity at room temperature of 2 × 10−2 S · m−1, even in the absence of dopants. The temperature dependence of the conductivity for the C8 derivative, over the range ‐ 50 to + 200°C, is given, to a good approximation, by σ = 1.5 · exp [‐ Ea/(kB · T)] S · m−1 with an activation energy Ea of 0.11 eV (2.5 kcal/mole). This material could be an example of an intrinsic, one‐dimensional conducting polymer.
Collision‐induced dissociation reactions of o‐, m‐ and p‐methoxyphenyl anions in the gas phase
Authors: Visser Remco , Maas Wilfried P. M. , Nibbering Nico M. M.
Published: September 2010

On the basis of collision‐induced‐dissociation experiments, we show that o‐, m‐ and p‐methoxyphenyl anions, generated under negative‐chemical‐ionization (NCI) conditions from the corresponding ethyl methoxybenzoates, are distinct species.

The main collision‐induced‐dissociation channel for the o‐methoxyphenyl anion is formaldehyde loss. This ion also loses a CH2 moiety, which indicates that it can rearrange to a stable C6H5OCH2− primary carbanion.

Methyl‐radical loss is the major collision‐induced‐dissociation channel for both the m‐ and p‐methoxyphenyl anions. The kinetic energy release accompanying this dissociation is significantly larger for the former anion than for the latter. It is suggested that this is due to a greater stability of the product radical ion, if generated from the m‐methoxyphenyl anion rather than from the p‐methoxyphenyl anion.
Chemo‐enzymatic synthesis and characterization of L‐tryptophans selectively 13C‐enriched or hydroxylated in the six‐membered ring using transformed Escherichia coli cells
Authors: van den Berg E. M. M. , Jansen F. J. H. M. , de Goede A. T. J. W. , Baldew A. U. , Lugtenburg J.
Published: September 2010

L‐(3a‐13C)‐ And L‐(6‐13C)tryptophan have been synthesized from simple labelled compounds via a single reaction scheme based on the conversion of 1,3‐cyclohexanedione into indole. The labelled indoles have been converted in one step into the corresponding L‐tryptophans using transformed Escherichia coli cells with large amounts of the enzyme, tryptophan synthetase. The same reaction scheme has been used for the synthesis of 4‐ and 7‐indolol. These hydroxyindoles together with 5‐indolol have been converted into 4‐, 7‐ and 5‐hydroxy‐L‐tryptophan, respectively, using the Escherichia coli cells. The latter compound is the immediate precursor of the neurotransmitter, serotonin. It appears that 7‐indolol is the only indole derivative which is converted faster than unsubstituted indole by the enzyme, tryptophan synthetase. With the preparation of L‐(3a‐13C)‐ and L‐(6‐13C)tryptophan, we have completed the series of indoles and L‐tryptophans with a stable isotope (13C, 15N or 2H) in the aromatic ring. In this paper, we also discuss the NMR parameters of these mono‐isotopically labelled systems.
Modification of papain with a NAD(P)H analogue. Reactivity towards charged substrates and enhanced stability towards acid catalyzed hydration
Authors: Broos Jaap , Kellogg Richard M.
Published: September 2010

An N‐alkylnicotinamidium salt has been linked covalently to Cys 25 of papain and thereafter reduced to the 1,4‐dihydro form. Reactions of this material have been examined.
Phosphino‐stabilized allyl anions and trimethylenemethane dianions
Authors: van Doom J. A. , van der Heijden H.
Published: September 2010

Phosphino‐stabilized allyl anions are formed by deprotonation of phosphinopropenes with alkyllithium. A double deprotonation of 2‐diphenylphosphinomethyl‐3‐diphenylphosphinopropene leads to interesting phosphino‐stabilized trimethylenemethane dianions. Alkylation with methyl iodide occurs at a carbon atom and not at a phosphorus centre.
Stereoselective reduction of benzoin by the NADH model 3‐(dimethylcarbamoyl)‐1,2,4‐trimethyl‐1,4‐dihydropyridine
Authors: Beijer Nicoline A. , Vekemans Jozef A. J. M. , Buck Henk M.
Published: September 2010

The Mg(ClO4)2‐induced reduction of racemic benzoin by the racemic NADH model compound 3‐(dimethylcarbamoyl)‐1,2,4‐trimethyl‐1,4‐dihydropyridine (1), in accordance to Cram's rule, leads exclusively to meso‐1,2‐diphenyl‐1,2‐ethanediol. However, while R‐1 equally reduces 5‐benzoin to afford meso‐1,2‐diphenyl‐1,2‐ethanediol, S‐1 is reluctant to react with S‐benzoin. The intermediacy of a strictly organized transition state, composed of chelated substrate, dihydropyridine and magnesium ion is involved.
Selective nucleophilic displacement of a methoxy group in 1,2,3‐trimethoxybenzenes
Authors: Budzelaar P. H. M. , van Doorn J. A.
Published: September 2010

A methoxy group in 1,2, 3‐trimethoxybenzenes can be readily displaced by a butyl group via reaction with butyllithium in hexane. The reaction probably proceeds via an addition‐elimination mechanism. There appears to be a qualitative relation between the coefficient of the LUMO at the central C‐O carbon atom and the rate of the reaction.
Synthesis of oligodeoxynucleotides containing thymidines linked via an internucleosidic‐(3′‐5′)‐methylene bond
Authors: Veeneman G. H. , van der Marel G. A. , van den Elst H. , van Boom J. H.
Published: September 2010

Condensation of N3‐benzoyl‐5′‐O‐dimethoxytrityl‐3′‐O‐(4‐penten‐1‐oxymethyl)‐thymidine with N3‐benzoyl‐3′‐O‐methoxyacctyl‐thymidine, in the presence of N‐iodosuccinimide, afforded a fully‐protected thymidine dimer having an internucleosidic‐(3′‐5′)‐methylene linkage. The latter was utilized in the preparation, in solution and on a solid support, of DNA‐fragments containing one or more T‐CH2‐T dimer(s).
Dimetallation of benzene
Authors: Lochmann L. , Fossatelli M. , Brandsma L.
Published: September 2010

Using the combination of n‐butyllithium and soluble potassium t‐alkoxides higher ratios of di‐and mono‐metallated benzene have been attained than with n‐butyllithium and the insoluble t‐BuOK.
A liquid‐crystalline poly(iminomethylene) with cholesterol‐containing pendant groups
Authors: van Walree C. A. , van der Pol J. F. , Zwikker J. W.
Published: September 2010

Two poly(iminomethylenes) with cholesterol‐containing pendant groups were synthesized. Using an aliphatic spacer, a liquid‐crystalline polymer was obtained, with equal amounts of right‐and left‐handed helices. With phenylene as bridging group, only oligomers resulted, probably for steric reasons. Some novel liquid‐crystalline esters of cholesterol are also presented.
Synthesis of plastoquinone derivatives with different structures of the side chain
Authors: Liu Benli , Gu Lianquan , Zhang Jingling
Published: September 2010

Two schemes for the synthesis of plastoquinone derivatives with ω‐substituted alkyl side chains have been developed, based on radical alkylation of 2,3‐dimethyl‐1,4‐benzoquinone with ω‐substituted carboxylic and/or dicarboxylic acids in the presence of S2O2−8 and Ag+. In Scheme 1, radical alkylation of 2,3‐dimethyl‐1,4‐benzoquinone with 11‐bromoundecanoic acid, in the presence of (NH4)2S2O8 and AgNO3, gave 2,3‐dimethyl‐5‐(10‐bromodecyl)‐1,4‐benzoquinone, which, after hydration, gave 2,3‐dimethyl‐5‐(10‐hydroxydecyl)‐1,4‐benzoquinone. Esterification of 2,3‐dimethyl‐5‐(10‐hydroxydecyl)‐1,4‐benzoquinone with different acyl chlorides gave 2,3‐dimethyl‐5‐(10‐acyloxy‐decyl)‐1,4‐benzoquinone. In Scheme 2, radical alkylation of 2,3‐dimethyl‐1,4‐benzoquinone with adipic acid, in the presence of K2S2O8 and AgNO3, gave 2,3‐dimethyl‐5‐(4‐carboxybutyl)‐1,4‐benzo‐quinone, which was converted to 2,3‐dimethyl‐5‐[4‐(alkoxycarbonyl)butyl]‐1,4‐benzoquinone by esterification with different alcohols in the presence of dicyclohexylcarbodiimide. 2,3‐Dimethyl‐5‐(8‐carboxyoctyl)‐1,4‐benzoquinone and 2,3‐dimethyl‐5‐[8‐(alkyloxycarbonyl)octyl]‐1,4‐benzoquinone were similarly synthesized from 2,3‐dimethyl‐1,4‐benzoquinone and sebacic acid. Plastoquinone derivatives having different kinds of double bonds in the side chain with and without a 6‐methyl group were synthesized from 2,3,5‐trimethyl‐1,4‐benzoquinone and 2,3‐dimethyl‐1,4‐benzoquinone by successive reactions with (l)NaBH4; (2)KHSO4, different kinds of allylic alcohols; (3) Ag2O. The allylic alcohols were prepared from their corresponding aldehydes by reduction with NaBH4. 2,3,6‐Trimethyl‐1,4‐benzoquinone was prepared from 2,3‐dimethyl‐1,4‐benzoquinone by radical methylation with acetic acids in the presence of K2S2O8+ AgNO3.