ISSN:0362-4803    

DOI:10.1002/jlcr.2580360502

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

Abstract3,5,6,7,8,8a‐Hexahydro‐7,7,8a‐trimethyl‐[6S‐(6α,8α,8αβ)]‐6,8‐methano‐2H‐1,4‐benzoxazino‐2‐one (2) was investigated as chiral auxiliary for asymmetric NCA nucleophilic synthesis of 6‐[18F]Fluoro‐L‐DOPA. Direct condensation of 3,4‐dimethoxy‐2‐[18F]fluorobenzaldehyde (1a) or 6‐[18F]fluoropiperonal (1b) in the presence of NaH with2gave the corresponding [18F]‐3‐[(2‐fluorophenyl)methylene]‐3,5,6,7,8,8a‐hexahydro‐7,7,8a‐trimethyl‐[6S‐(3Z,3α,6α,8α,8αβ)]‐6,8‐methano‐2H‐1,4‐benzoxazin‐2‐one derivative3aor3bas a single stereoisomer. L‐Selectride® promoted hydrogenation of the olefinic double bond of these derivatives, in presence of tertbutyl alcohol, afforded the corresponding [18F]‐3‐[(2‐fluorophenyl)methyl]‐3,5,6,7,8,8a‐hexahydro‐7,7,8a‐trimethyl‐[3S‐(3α,6α,8α,8αβ)]‐6,8‐methano‐2H‐ 1,4‐benzoxazin‐2‐one derivatives (4a,b) without affecting the orientation of diastereofacial discrimination. Deprotection of the derivatives4a,byielded 6‐[18F]fluoro‐L‐DOPA (e.e.>90%, 3% radiochemical yield (EOB), total synthesis time 125 min, specific activity>2000 mCi/μmol). Direct deprotection/reduction of the compounds3a,bprovides the enantiomeric mixture of 6‐[18F]fluoro‐D,L‐DOPA (10–12% radiochemical yield) and, after chiral separation, 6‐[18F]fluoro‐L‐DOPA (e.e. 98%, 4

ISSN:0362-4803    

DOI:10.1002/jlcr.2580360503

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractVigabatrin‐[6‐14C] ((R,S)‐4‐amino‐5‐hexenoic‐[6‐14C] acid) was synthesized by employing Wittig condensation of 1‐(1‐butenyl)‐2‐oxo‐5‐pyrrolidinecarboxaldehyde with methyl‐[14C]‐triphenylphosphonium iodide as the key step. The synthetic sequence involved 3 steps and produced the title compound in 70% overall yield with

ISSN:0362-4803    

DOI:10.1002/jlcr.2580360504

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractSynthetic methods for the preparation of β‐deuterium labeled 2‐keto‐4‐methylbutyric acid were investigated. Vinyl chloride was first reacted with the ethyl oxalyl chloride moiety using aluminum chloride as condensing agent and the addition of methyl mercaptan followed. Deuterium labeling was achieved by using NaBD4reduction in

ISSN:0362-4803    

DOI:10.1002/jlcr.2580360505

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractProtein structure determination by modern NMR techniques is greatly facilitated using15N‐ and13C‐labeled proteins. Labeling of proteins that are overexpressed in mammalian cells is a difficult task that requires a growth medium consisting of algal hydrolysates supplemented with labeled amino acids. Although most of the amino acids can be obtained to prepare an isotopically labeled growth medium for mammalian cells,[U‐13C,15N]‐cysteine is not available, hampering the backbone and cysteine side‐chain assignments and structure determination in the vicinity of the cysteine residues. A synthesis of D,L‐[U‐13C,15N]‐cysteine hydrochloride in good overall yield is described which makes use of readily available15N‐ and13C‐labeled starting materials and will facilitate heteronuclear multidimensional NMR studies of proteins that are overexpressed

ISSN:0362-4803    

DOI:10.1002/jlcr.2580360506

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

Abstract14C‐Labelled 6‐hydroxy‐5,7‐dimethyl‐2‐(methylamino)‐4‐(3‐pyridylmethyl)‐benzothiazole dihydrochloride (14C‐E3040 dihydrochloride), required for a study of the phrmacokinetic profile of E3040, a novel dual inhibitor of 5‐lipoxygenase and thromboxane A2synthetase, was synthesized in one step using [2‐14C]‐1‐methyl‐2‐thiourea as the labelled starting material.14C‐E3040 dihydrochloride with a specific activity of 58.0mCi/mmol was prepared in 60%

ISSN:0362-4803    

DOI:10.1002/jlcr.2580360507

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractSynthesis of the potent immunosuppressive agent, mycophenolate mofetil (1) labelled with carbon‐14 is described. Methoxyethoxymethyl (MEM) protected mycophenolate norbromide (9) was prepared from unlabelled mycophenolic acid (2) using a modified Hunsdiecker reaction. A three step synthesis furnished the title compound, having a specific activity of 53.8 mCi/mmol, in 49.5% overall yield from K14C

ISSN:0362-4803    

DOI:10.1002/jlcr.2580360508

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe synthesis of [8‐14C]‐2,6‐dichloro‐9H‐purine (2), a radiolabelled precursor for preparing14C‐labelled nucleosides, is described. Triethyl[14C]orthoformate was reacted with 4,5‐diamino‐2,6‐dichloropyrimidine (1) in acetonitrile at 90°C with methanesulfonic acid as catalyst to generate2in 84% radiochemical yield. Reaction of2with 1‐O‐acetyl‐2,3,5‐tri‐O‐benzoyl‐D‐ribofuranose produced [8‐14C]‐9‐(2,3,5‐tri‐O‐benzoyl‐β‐D‐ribofuranosyl)‐2,6‐dichloropurine (3) in 86% yield. The radiochemical purity of 3 was higher than 98% with a specific activity of 36 mCi/mmol. This method has general a

ISSN:0362-4803    

DOI:10.1002/jlcr.2580360509

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

Abstract6,6,6‐2H3‐3Z‐Hexenal (3b) has been prepared in 89% yield and in greater than 94% purity by the oxidation of 6,6,6‐2H3‐3Z‐Hexen‐1‐ol (2b) with the Dess/Martin periodinane (1) in fluorotrichloromethane (freon 11). Use of the freon solvent greatly improved the recovery of this volatile aldehyde. Similarly the oxidation of 3,4‐2H2‐3Z‐hexen‐1‐ol (5) yielded 3,4‐2H2‐3Z‐hexenal (6) in a 92% isolated yield with a purity of greater than 99%. 3,4‐2H2‐3Z‐Hexen‐1‐ol (5) was prepared in 87% by the catalytic deuterogenation of 3‐hexyn

ISSN:0362-4803    

DOI:10.1002/jlcr.2580360510

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

Abstract4‐Hydroxy‐2(E)‐nonen‐1‐al‐diethylacetal3(HNE‐DEA) was prepared by condensation of the Grignard compound derived from propiolaldehyde diethylacetal and n‐hexanal followed by reduction of the resulting 4‐hydroxy‐2‐nonyn‐1‐al‐diethylacetal2with LiAlH4according to the literature procedure with minor modifications. Swern oxidation [DMSO + (COCl2)] of3gave 30% yield of 4‐oxo‐2(E)‐nonen‐1‐al‐diethylacetal5. [3H]NaBH4and [2H]NaBH4reduction of5gave rise respectively to [4‐3H]HNE‐DEA (specif

ISSN:0362-4803    

DOI:10.1002/jlcr.2580360511

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY