Studien über äther‐artige Verbindungen, III.: Polyäther‐säuren vom Typus R. O. [CH
 2
 . CH
 2
 . O]
 n
 . CH
 2
 . COOH

Palomaa, M. H.; Siitonen, T. A.

doi:10.1002/cber.19300631127

Cited by 18 publications

(3 citation statements)

References 4 publications

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“…3,6,9-Trioxadecanoyl chloride (from the reaction of 3.7 g 3,6,9-trioxadecanoic acid [22] and thionyl chloride) was added dropwise over 15 min to a stirred solution of 2,3,6,7,10,11 -hexa-hydroxytriphenylene l b (972 mg) in pyridine under an atmosphere of nitrogen. A mildly exothermic reaction occurred and a white precipitate formed.…”

Section: Synthesis Of Discoid Amphiphilesmentioning

confidence: 99%

Designing new lyotropic amphiphilic mesogens to optimize the stability of nematic phases

et al. 1986

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Section: Synthesis Of Discoid Amphiphilesmentioning

confidence: 99%

Designing new lyotropic amphiphilic mesogens to optimize the stability of nematic phases

et al. 1986

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“…C 73.93 H 7.12 N 2.59 . 5) (3R,4R)-3,4-Bis(diphenylphosphino)-l-[(bmethoxyethoxy)acetyl]pyrrolidin (6g): Zu einer Losung von 1.005 g (2.28 mmol) 6a und 0.19 ml(2.33 mmol) Pyridin in 10 ml CH2C12 werden bei -20°C 0.360 g (2.33 mmol) (2-Methoxyethoxy)acetylchlorid 12) gegeben. Die Losung wird bei Raumtemp.…”

Section: Experimenteller Teilunclassified

Enantioselektive Katalyse, 4. Synthese N‐substituierter (R,R)‐3,4‐Bis(diphenylphosphino)‐pyrrolidine und Anwendung ihrer Rhodiumkomplexe zur asymmetrischen Hydrierung von α‐(Acylamino)acrylsäure‐Derivaten

et al. 1986

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Eine einfache Synthese von (R.R)-3,4-Bis(diphenylphosphino)pyrrolidin (6a)und Rhodium Complexes for the Asymmetric Hydrogenation of a-(Acy1arnino)acrylic Acid DerivativesA simple synthesis of (R,R)-3,4-bis(diphenylphosphino)pyrrolidine (6a) and some N-substituted derivatives 6b-m is described. 61 and 6m are optically active tetraphosphanes, composed of two (R,R)-3,4-bis(diphenylphosphino)pyrrolidine units and a dicarboxylic residue. The structure of the parent compound 6a was determined by X-ray diffraction. From the phosphanes 6a -m the cationic 1,5-cyclooctadiene-bisphosphane-rhodium complexes 7a-rn were prepared. The complexes 71 and 7m are ligand bridged bis(rhodium) dications. The complexes 7a-m were used for the asymmetric catalytic hydrogenation of the a-(acy1amino)acrylic acid derivatives 9a -I. Enantiomeric excesses up to 100% were achieved. Between 1 and 70 at the optical yields do not depend on the hydrogen pressure. The substrateJcatalyst ratio can be as high as 5ooOoJ1. *) Zusammenarbeit bei der Verkiirzung der urspriinglich langeren Synthese von 6b.

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“…Methoxy-acetylated galactal 1b showed a similar behaviour. Acceptable results in regioselective removal of the 2-methoxyethoxyacetyl group, 11 resembling the 2methoxyethoxyethyl (MEE) esters, 12 were obtained by reacting 1c with protease P (Aspergillus melleus). 10a A mixture of the 6-O-(2c) and prevailing (1:3) 3-O-deprotected product 3c was isolated.…”

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Selectively Deprotectable Carbohydrates Based on Regioselective Enzymatic Reactions

Pfau¹,

Kunz²

1999

Synlett

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Galactals and 2-azido-2-deoxy-galactopyranosides equipped with a set of selectively removable hydroxy protecting groups are synthesized on the basis of lipase-catalyzed regioselective deacylation and acylation reactions.Selective deprotection of one out of a number of hydroxy groups is a prerequisite of carbohydrate chemistry. 1 This holds true, in particular, for the synthesis of complex oligosaccharides 2 and for the application of carbohydrate scaffolds in combinatorial syntheses. 3 Enzyme-catalyzed reactions have the general advantage of mild reaction conditions and high efficiency while their application is limited by substrate specificity. Ester hydrolysis catalyzed by lipases, esterases and proteases received increasing interest in protecting group chemistry during the past decade. 4 It was shown for the synthesis of glycosyl amino acids and glycopeptides that alternative selective deprotection either of the peptide carboxylic function or the carbohydrate hydroxy groups can be accomplished using lipases of different origin. 5 However, a sufficiently regioselective differentiation of the O-acetylated carbohydrate functionalities has not been achieved. 5,6 A few exceptions concern the selective hydrolysis at the primary 6-position of octanoyl-and pentanoyl glucopyranosides, 7 at the allylic 3-position of O-acetylated glycals, 8 and deacetylations of nucleotides. 9Aiming at a reliably regioselective deprotection of O-acylated hydroxy groups, we subjected galactals 1 carrying various acyl protecting groups to enzymatic hydrolysis using 25 lipases, 5 proteases and one esterase. The reactions (Scheme 1) were carried out in aq. 0.2 M phosphate buffer of pH 7 at various temperatures.The best results of regioselective enzymatic hydrolysis of esters 1 obtained in this systematic investigation are quoted in Table 1. Treatment of tri-O-acetyl-galactal with lipase A6 (Aspergillus niger) 10a produced a mixture of the 6-O-(2a) and 3-O-deblocked (3a) diacetyl-galactals in a ratio of 3:2. Hydrolysis of 1a catalyzed either by lipase WG (wheat germ) 10b or pig liver esterase (PLE-A) 10a for 2 h gave mixtures of the 6-O-(2a) and 3,6-O-deacylated (4a) compounds which could be separated (Table 1). Application of PLE-A for only 30 min resulted in a sufficiently selective formation of the 6-O-deblocked galactal 2a, however, with incomplete conversion of 1a. Methoxyacetylated galactal 1b showed a similar behaviour. Acceptable results in regioselective removal of the 2-methoxyethoxyacetyl group, 11 resembling the 2-methoxyethoxyethyl (MEE) esters, 12 were obtained by reacting 1c with protease P (Aspergillus melleus). 10a A mixture of the 6-O-(2c) and prevailing (1:3) 3-O-deprotected product 3c was isolated.Optimal regioselective deprotections were achieved with O-isobutyryl ( i But) protected galactal 1d. Hydrolysis catalyzed by lipase CCL from Candida rugosa (Sigma Type Enzyme-catalyzed regioselective hydrolysis of galactals bearing different acyl protecting groups Scheme 1Downloaded by: University of British Columbia. Copyrighted...

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Studien über äther‐artige Verbindungen, III.: Polyäther‐säuren vom Typus R. O. [CH ₂ . CH ₂ . O] _n . CH ₂ . COOH

Cited by 18 publications

References 4 publications

Designing new lyotropic amphiphilic mesogens to optimize the stability of nematic phases

Designing new lyotropic amphiphilic mesogens to optimize the stability of nematic phases

Enantioselektive Katalyse, 4. Synthese N‐substituierter (R,R)‐3,4‐Bis(diphenylphosphino)‐pyrrolidine und Anwendung ihrer Rhodiumkomplexe zur asymmetrischen Hydrierung von α‐(Acylamino)acrylsäure‐Derivaten

Selectively Deprotectable Carbohydrates Based on Regioselective Enzymatic Reactions

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Studien über äther‐artige Verbindungen, III.: Polyäther‐säuren vom Typus R. O. [CH 2 . CH 2 . O] n . CH 2 . COOH

Cited by 18 publications

References 4 publications

Designing new lyotropic amphiphilic mesogens to optimize the stability of nematic phases

Designing new lyotropic amphiphilic mesogens to optimize the stability of nematic phases

Enantioselektive Katalyse, 4. Synthese N‐substituierter (R,R)‐3,4‐Bis(diphenylphosphino)‐pyrrolidine und Anwendung ihrer Rhodiumkomplexe zur asymmetrischen Hydrierung von α‐(Acylamino)acrylsäure‐Derivaten

Selectively Deprotectable Carbohydrates Based on Regioselective Enzymatic Reactions

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Studien über äther‐artige Verbindungen, III.: Polyäther‐säuren vom Typus R. O. [CH ₂ . CH ₂ . O] _n . CH ₂ . COOH