Statistical aspects of chemical analysis

Following a brief statement of certain fundamental principles, methods of sampling are dicussed which enable the informaiton sought by the analyst to be obtained as economically as possible. The need for proper randomisation both in sampling and in performing analyses is stressed and a short account is given of the use of 'quality control' charts in analytical work. Attention is drawn to the possibility of estimating the standard error from the range. A method of extracting the maximum information from analytical investigation involving the estimation of a ratio is described. The advantages of the 'factorial' as opposed to the 'classical' type of experimental design are demonstrated and reference is made to the value of carrying out an analysis of variance when examining the experimental data.     

Some metallofluorescent derivatives of 2,2'-diamino-diphenyl-n,n,n',n'-tetraacetic acid

The N,N,N',N'-tetraacetic acid derivatives of five 4,4'-disubstituted 2,2'-diaminodiphenyls have been prepared and their fluorescent properties examined. 2,2'-Diaminodiphenyl-4,4'-dicarboxylic acid-N,N,N',N'-tetraacetic acid exhibits intense fluorescence in aqueous solution above pH 4, and forms stable non-fluorescent l:1 complexes with copper(II) and nickel(II) ions at pH 7.5. The quenching of the fluorescence of the compound by nickel(II) may be used in the fluorimetric determination of nickel.     

Laser-induced low-temperature fluorescence spectroscopy

The absorption and fluorescence spectra of molecules are often very sharp under cryogenic sampling conditions. When a tunable laser is used to excite fluorescence, selective determinations of individual constituents of very complex samples are possible, and the highly resolved fluorescence spectra can serve as 'molecular fingerprints'     

2'-deoxyribonucleoside 3'-aryl phosphoranilidates: Key intermediates in the stereospecific synthesis of 2'-deoxyribonucleoside cyclic 3',5'-phosphorothioates and dinucleoside(3'→5')-phosphoranilidates

Phosphorylation of the 5'-O-monomethoxytrityl-2'-deoxyribonucleosides by means of aryl phosphoranilidochloridates gives the diastereoisomers of 5'-O-monomethoxytrityl-2'-deoxyribonucleoside 3'-aryl phosphoranilidates. Their separation can be performed by means of chromatographic techniques. They can be further converted to the 2'-deoxyribonucleoside cyclic 3'-5' phosphoranilidates, which are intermediates in the stereospecific synthesis of 2'-deoxyribonucleoside cyclic (3'-5')phosphorothioates of known absolute configuration at phosphorus.     

Comment on the energy variation method

It is pointed out that the classical minmax principle plays a significant role in the derivation of Hendekovi?'s results. Secondly, we conjecture that Hendekovi?'s results may be generalized.     

5'-Substituted 2,2'-anhydrouridines

3',5'-Di-O-acetyl-2'-halogenouridines (1a, 1c and 1d) can be partially deacetylated at C-5' by transesterification with methanol-HCl, providing the 3'-O-acetyl derivatives 2a–2c. These can be converted into the 5'-O-mesyl derivatives 3a–3c, and latter into the 5'-chloro compounds 3d-3f. All 5'-substituted 2'-halogeno compounds give the corresponding 2,2'-anhydrouridine derivatives 4a–4c on treatment with NaOMe. Structures were proved by IR and ¹H-NMR.     

Electrostatic methods of zone location for paper chromatographs : A chromatograph humidiser

This paper describes a “humidiser” or conditioner employed to sensitise chroimatographic spots of weakly conductive solute It may be used with BLAKL'S R Rf. or his Es D, methods Special reference is made to its use in conjunction with automatic zone location. A photograph of this apparatus is reproduced 'The spot edge effect' is rcordcd (A phenomenon observcd during spot localization)     

Structure of amauromine,a new hypotensive vasodilator produced by amauroascus sp.

The structure of amauromine, a novel alkaloid with potent vasodilating activity was determined chemically and spectroscopically to be (5aS, 7aS, 8aR, 13aS, 15aS, 16aR)-8a, 16a-bis-(1,l-dimethyl-2-propenyl)-5a, 8,8a,13,13a,15a,16,16a-octahydropyrazino [1',2':1, 5;4', 5':1',5']dipyrrolo[2,3-b:2',3'-b']- diindole-7, 15(5H,7aH)-dione.     

Lithiation of 3',5'-O-(tetraisopropyldisiloxane-1,3-diyl)-2'-deoxyuridine: synthesis of 6-substituted 2'-deoxyuridines

Synthesis of 6-substituted 2'-deoxyuridines can be effected by lithiation of 3',5'-$\text{O}$-(tetraisopropyldisiloxane-1,3-diyl)-2'-deoxyuridine with LDA followed by the reaction of its lithio derivative with electrophiles. This method provides a general, regiospecific and simple route to various types of 6-substituted 2'-deoxyuridines which have, so far, been known to be difficult to prepare.     

Electrophoric release tags: Ultrasensitive molecular labels providing multiplicity

Electrophoric release tags are a new class of analytical reagents which function as molecular labels. These tags can be more sensitive than radioisotopes and their potential for multiplicity allows release-tagged reagents to be used as 'teams' in chemical analysis. Monoclonal antibodies, nucleic acid probes, receptor ligands and enzyme substrates may all benefit from this approach.     

Microbiological transformations—XII: Microbiological reduction of racemic 1-(2',2',3'-trimethyl-cyclopent-3'-en-1'-yl)propan-2-one and 1-(2',2',3'-trimethyl-cyclopent-3'-en-1'-yl)butan-2-one by rhodotorula mucilaginosa

The microbiological reduction of (±)-l-(2',2',3'-trimethylcyclopent-3'-en-l'-yl)-propan-2-one (4) and (±)-1-(2',2',3'-trimethylcyclopent-3'-en-l'-yl)-butan-2-one (5) by Rhodotorula mucilaginosa was investigated. Both enantiomers of 4 are reduced stereospecifically to corresponding alcohols; (+)-(2S, l'R)-(2',2',3'-trimethylcyclopent-3'-en-l'-yl)-propan-2-ol (6) and (-)-(2S,l'S)-(2',2',3'-trimethylcyclopent-3'-en-l'-yl)-propan-2-ol (7). p ]The substrate selectivity in the reduction of 5 was observed: R enantiomer of 5 yields stereospecifically (+)-(2S,1'R)-(2',2',3'-trimethylcyclopent-3'-en-l'-yl)-butan-2-ol (8) while S(-)5 remains unchanged.     

Synthesis of carbon-bridged 8,5'-cyclopurine nucleosides: Nucleosides and nucleotides—XXIV1

Treatment of 2',3'-O-isopropylidene-5'-deoxy-8,5'-cycloadenosine with selenium oxide afforded the 5'-oxo-compound. Reduction of the product with sodium borohydride proceeded stereoselectively to give the 8,5'(S)-cycloadenosine. The 5'-R-isomer was obtained by the inversion of the 5'-OH group of the S-epimer via the mesyloxy derivative. Hydrolytic deamination of 8,5'-cycloadenosines gave the inosine counterparts. Photo-irradiation of 2',3'-O-isopropylidene-5'-deoxy-5'-phenylthio-N²-benzoylguanosine afforded the 8,5'-cyclo-5'-deoxyguanosine, which was also converted to the 5'-oxo-derivative. Reduction of the product also afforded to give the 8,5'-(S)-cycloguanosine. The CD spectra of these cyclonucleosides reflect the chiralities at the 5'-position.     

Synthesis of the natural enantiomers of ascochlorin,ascofuranone and ascofuranol

Three fungal metabolites with a common structural feature as prenylated phenols were synthesized in their naturally occurring and optically active forms: ascochlorin [(2'$\text{E}$,4'$\text{E}$,1'$\text{R}$,2'$\text{R}$,6'$\text{R}$)-(-)-5-chloro-2,4-dihydroxy-6-methyl-3-[5'-(1',2',6'-trimethyl-3'-oxo-cyclohexyl)-3'-methyl-2', 4'-pentadienyl] benzaldehyde], ascofuranone [(2'$\text{E}$,6'$\text{E}$,1'$\text{S}$)-(-)-5-chloro-2, 4-dihydroxy-6-methyl-3-[7'-(3',3'-dimethyl-4'-oxo-2'-oxacyclopentyl)-3',7'-dimethyl -2', 6'-heptadienyl] benzaldehyde] and ascofuranol [(2'$\text{E}$,6'$\text{E}$,1'$\text{S}$,4'$\text{S}$)-(-)-5-chloro-2,4-dihydroxy-6-methyl-3-[7'-(3', 3'-dimethyl-4'-hydroxy-2'-oxacyclopentyl)-3', 7'-dimethyl-2',6'-hepta-dienyl]benzaldehyde ]. (+)-Ascofuranone and (+)-ascofuranol were also synthesized. By the present synthesis the absolute configuration of the natural (-)-ascofuranol was established as (1'$\text{S}$,4'$\text{S}$).     

Synthesis of (±)-ascochlorin, (±)-ascofuranone and LL-Z1272

Three antibiotics with a common structural feature as prenylated phenols were synthesized: (±)-ascochlorin (5 - chloro-2,4 - dihydroxy - 6 - methyl - 3 - [(2E',4/E') - 5' - (1′,2′,6′ - trimethyl - 3′-oxocyclohexyl) - 3' - methyl - 2',4' - p benzaldehyde), (±)-ascofuranone (5 - chloro - 2,4 - dihydroxy - 6 - methyl - 3 - [(2'E,6'E) - 7' - (3′,3′ - dimethyl - 4′ - oxo - 2′ - oxacyclopentyl) - 3',7 -dimethyl - 2',6' - heptadienyl] benzaldehyde) and LL-Z1272α (5 - chloro - 2,4 - dihydroxy - 6 - methyl -3 - [(2'E,6'E) - 3',7',11' - trimethyl - 2',6', 10' - dodecatrienyl] benzaldehyde)     

Polybrominated oxydiphenol derivatives from the sponge dysidea herbacea: Structure determination by analysis of 13C spin-lattice relaxation data for quaternary carbons and 13C-1H coupling constants

Five polybrominated oxydiphenol derivatives have been isolated from various Great Barrier Reef collections and one Fijian collection of the sponge Dysidea herbacea: 3,4',5,6,6'-hexabromo-2, 2'-oxydiphenol (11), 3,4',5,6,6'-pentabromo-2,2'-oxydiphenol (12), 3.4',5,6,6'-pentabromo-2,2'-oxydiphenol 1-methyl ether (13), 3,4,4',5,6'-pentabromo-2,2'-oxydiphenol 1,1'-dimethyl ether (14) and 3,4',5,6'-tetrabromo-2,2'-oxydiphenol 1'-methyl ether (15).The structure of the first member of this series is determined by a new method involving ¹³C spin-lattice relaxation data. The contributions of nearby hydrogens to quaternary carbon spin-lattice relaxation times are calculated for various possible structures and compared with the experimental data, leading to an unequivocal proof of structure. The structures of the remaining compounds in the series are established principally by analysis of ¹³C chemical shifts and ¹³C-¹H coupling constants.     

Six new metabolites from the brown alga halidrys siliquosa (phaeophyta,fucales)

Six monomethyl hydroquinols with oxygenated diterpene side chains have been isolated from the brown alga Halidrys siliquosa. We have isolated 5',12'-dioxohalidrol (1), 5',12'-dioxoisohalidrol (2), 12'α-hydroxy-5',13'- dioxohalidrol (3), 12'α-hydroxy-5',13'-dioxoisohalidrol (4), 12'β-hydroxy-5',13'-dioxoisohalidrol (5) and 5'-hydroxy-12-oxohalidrol (6).     

Studies of nucleosides and nucleotides—LXXIV: Purine cyclonucleosides—34 a new method for the synthesis of 2'-substituted 2'-deoxyadenosines

8,2'-O-Cycloadenosine was protected at 3' and 5'-OHs with acetyl groups and cleaved using liq. H₂S. Subsequent dethiolation and mesylation gave 2'-O-mesyl-3',5'-di-O-acetyl-arabinosyladenine (6). When 6 or its deacetylated parent compound (7) was heated with sodium azide in DMF, 3'-azido-3'-deoxyxylofuranosyladenine (9) was the only product. The cyclonucleoside was then protected with tetrahydropyranyl groups and subjected to a similar series of reactions as above to give 2'-O-mesyl-3',5'-di-O-tetrahydropyranylarabinosyladenine (14). The compound 14 was heated with sodium azide after which acidic deprotection afforded 2'-azido-2'-deoxyadenosine (16). Hydrogenation of 16 gave 2'-amino-2'-deoxyadenosine (18). 2'-Chloro-2'-deoxyadenosine (19) was also obtained by treatment of 14 with lithium chloride and subsequent deprotection. UV, IR and NMR spectral data of these compounds are described.     

Polybrominated diphenyl ethers from Dysidea herbacea,Dysidea chlorea and Phyllospongia foliascens

The marine sponges Dysidea herbacea, D. chlorea and Phyllospongia foliascens were differentiated with difficulty in the field. D. herbacea contained 2-(2',4'-dibromophenoxy)-3,4,5-tribromophenol (1), 2-(2',4'-dibromophenoxy)-4,5,6-tribromophenol (2) and 2-(2',4'-dibromophenoxy)-3,5-dibromophenol (6). D. chlorea contained only 2-(2',4'-dibromophenoxy)-4,6-dibromophenol(3), a compound previously reported as a metabolite of D. herbacea. Phyllospongia foliascens contained 2-(3',5'-dibromo-2'-methoxy-phenoxy)-3,5-dibromoanisole (7) and a 1:2 mixture of 2-(3',5'-dibromo-2'-hydroxyphenoxy)-3,5,6-tribromophenol (8) and 2-(3',5'-dibromo-2'-hydroxyphenoxy)-3,4,5,6-tetrabromophenol (9).     

An in vitro comparison of microdialysis relative recovery of Met- and Leu-enkephalin using cyclodextrins and antibodies as affinity agents

Cyclodextrins and antibodies have been used as affinity agents to improve relative recovery during microdialysis sampling. Two neuropeptides, methionine-enkephalin (ME) and leucine-enkephalin (LE), were chosen to compare the use of cyclodextrins and antibodies as possible affinity agents for improving their relative recovery across polycarbonate and polyethersulfone membranes during in vitro sampling. Cyclodextrins (CD) including β-CD, 2-hydroxypropyl-β-cyclodextrin (2HPβ-CD), and γ-CD gave improvements of relative recovery for both peptides of less than 2-fold as compared to controls. Comparisons of relative recovery between tyrosine–glycine–glycine, tyrosine, and phenylalanine using different cyclodextrins in the perfusion fluid were also obtained. Inclusion of an antibody against met-enkephalin in the microdialysis perfusion fluid resulted in relative recovery increases of up to 2.5-fold. These results show that using antibodies as affinity agents during microdialysis sampling may be more effective agents to improve the relative recovery of these opioid neuropeptides.     

Synthese de la cyclo-5'-8 desoxy-5' adenosine: stereochimie et mecanisme de la cyclisation d'un derive de l'iodo-5' adenosine par le zinc

N,N'-Dibenzoyl 2', 3'-O-isopropylidene 5'-deoxy 5'-iodo adenosine can efficiently transformed into the corresponding 5',8-cyclo-7,8-dihydronucleoside by zinc in pyridine. Only one diastereoisomer is obtained. By spin decoupling and NOE techniques at 250 MHz, the R-configuration at C-8 was established. This compound showed typical dihedral angles of about 90° for the vicinal protons H-1', H-2' and H-3', H-4'. Using adenosine derivatives stereospecifically labelled at C-5', it was demonstrated that the cyclisation occurs with racemisation at that position.