3-exo,3′-exo-(1R,1′R)-Bithiocamphor — a versatile source for functionally different 3,3′-bibornane derivatives, II. 1 An access to 3-exo,3′-exo-(1r,1′r)-bicamphor and related compounds

3-exo,3′-exo-(1R,1′R)-bicamphor (12) is obtained from 3-exo,3′-exo-(1R,1′R)-bithtiocamphor (3) by condensation with hydrazine hydrate followed by hydrolysis of the resulting dihydropyridazine 11. Deprotonation of 12 with NaH and subsequent treatment with potassium hexacyanoferrate (III) furnishes the 2,2′-dioxo-3,3′-bibornanylidene 13, whilst reduction of 12 with L1AlH₄ affords the 3,3′-biisoborneol 16. Further related transformations to various 2,2′-difunctional 3,3′-bibornane derivatives are described, which are could be of interest as chiral ligands     

Synthesis of 1,1′-methylenedi[(1R,1′R,3R,3′R,5R,5′R)-8-oxabicyclo[3.2.1]oct-6-en-3-ol] and derivatives: precursors of long-chain polyketides

Racemic 1,1′-methylene[(1RS,1′RS,3RS,3′RS,5RS,5′RS)-8-oxabicyclo[3.2.1]oct-6-en-3-ol] ((±)-6) derived from 2,2′-methylenedifuran has been resolved kinetically with Candida cyclindracea lipase-catalysed transesterification giving 1,1′-methylenedi[(1R,1′R,3R,3′R,5R,5′R)-8-oxabicyclo[3.2.1]oct-6-en-3-ol] (−)-6 (30% yield, 98% ee) and 1,1′-methylenedi[(1S,1′S,3S,3′S,5S,5′S)-8-oxabicyclo[3.2.1]oct-6-en-3-yl] diacetate (+)-8, (40% yield, 98% ee). These compounds have been converted into 1,1′-methylenedi[(4S,4′S,6S,6′S)- and (4R,4′R,6R,6′R)-cyclohept-1-en-4,6-diyl] derivatives.     

New heterocyclic derivatives of 1′- and 3′-amino-5′,6′,7′,8′-tetrahydro-2′-acetonaphthones

The preparation of 1′-and 3′-amino-5′,6′,7′,8′-tetrahydro-2′-acetonaphthones (IIIa and IIIb) is described, by reduction of the low temperature nitration products of 5′,6′,7′,8′-tetrahydro-2′-acetonaphtone (I). The structures of the nitro isomers (IIa and IIb), and the reduction products, IIIa and IIIb, were elucidated spectroscopically. By known reactions, a series of new heterocyclic compounds prepared from the o-aminoketones, IIIa and IIIb, resulted in two series of new heterocyclic compounds.     

1-Boraadamantane: reactivity towards mono-1-alkynyltin, -germanium and -silicon compounds — synthesis of 4-methylene-3-borahomoadamantanes

The reaction of 1-boraadamantane 1 with 1-alkynyltin (3), -germanium (4), and -silicon compounds (5) leads to enlargement of the tricyclic system by formation of 4-methylene-3-borahomoadamantanes (6–9). These are 1,1-organoboration reactions which proceed by cleavage of the M---C bond (M=Sn, Ge, Si). There is evidence for 1,1-deorganoboration which apparently take place much more readily than for non-cyclic analogues, most likely as the result of the strained tricyclic system. When 2-ethyl-1-boraadamantane (2) is used, again 3-borahomoadamantanes are formed, the isomers 15–18. The product distribution is sensitive to steric effects. However, it appears that the B---C(H)Et bond in 2 is slightly more reactive than the B---CH₂ bonds. All products were characterised by ¹H-, ¹¹B-, ¹³C-, ²⁹Si- and ¹¹⁹Sn-NMR.     

DNA with 3′‐5′‐Disulfide Links—Rapid Chemical Ligation through Isosteric Replacement

Efforts to chemically ligate oligonucleotides, without resorting to biochemical enzymes, have led to a multitude of synthetic analogues, and have extended oligomer ligation to reactions of novel oligonucleotides, peptides, and hybrids such as PNA. 1 Key requirements for potential diagnostic tools not based on PCR include a fast templated chemical DNA ligation method that exhibits high pairing selectivity, and a sensitive detection method. Here we report on a solid‐phase synthesis of oligonucleotides containing 5′‐ or 3′‐mercapto‐dideoxynucleotides and their chemical ligations, yielding 3′‐5′‐disulfide bonds as a replacement for 3′‐5′‐phosphodiester units. Employing a system designed for fluorescence monitoring, we demonstrate one of the fastest ligation reactions with half‐lives on the order of seconds. The nontemplated ligation reaction is efficiently suppressed by the choice of DNA modification and the 3′‐5′ orientation of the activation site. The influence of temperature on the templated reaction is shown.     

Bis[(dihydrogen pyrophosphato‐κ2O,O′)(2,2′:6′,2′′‐terpyridine‐κ3N,N′,N′′)copper(II)] 4.5‐hydrate

The title copper complex, [Cu(H₂P₂O₇)(C₁₅H₁₁N₃)]₂·4.5H₂O, consists of two very similar independent Cu(Tpy)H₂P₂O₇ monomeric units (Tpy is 2,2′:6′,2′′‐terpyridine) plus four and a half water molecules of hydration, some of which are disordered. Tpy units bind through the usual triple bite via their N atoms, and the H₂P₂O₇²⁻ anions coordinate through two O atoms from two different phosphate units. Each independent CuN₃O₂ chromophore can be described as a slightly deformed square pyramid, with one of them having a sixth, semicoordinated, O atom from a centrosymmetrically related CuN₃O₂ unit in a weakly bound second apical position suggesting an octahedral environment for the cation and weak dimerization of the molecule. The two independent complex molecules are connected via two strong O—H...O interactions between the phosphate groups to form hydrogen‐bonded dinuclear units, further linked into [111] columns, resulting in a very complex three‐dimensional supramolecular structure through a variety of classical and nonclassical hydrogen bonds, as well as π–π interactions.     

Stereoselective total synthesis of (+)-(6R,2′S)-cryptocaryalactone and (−)-(6S,2′S)-epi cryptocaryalactone

The total synthesis of (+)-(6R,2′S)-cryptocaryalactone and (−)-(6S,2′S)-epi cryptocaryalactone is reported based on stereoselective reduction of δ-hydroxy β-keto ester to install 1,3-polyol system, cis Wittig olefination, and lactonization as the key steps. The synthesis of (−)-(6S,2′S)-epi cryptocaryalactone is also reported using syn-benzylidene acetal formation and a preferential Z-Wittig olefination reaction and lactonization as the key steps.     

The chemistry of phenalenium system—II 7,8,2′,3′,4′,5′-Hexachloro-11-methoxy-6H-cyclopenta[a]pyrene-6-spiro-1′-cyclopenta-2′,4′-diene

7,8,2′,3′,4′,5′-Hexachloro-11-methoxy-6H-cyclopenta[a]pyrene-6-spiro-1′-cyclopenta-2′,4′-diene 5 has been obtained by the reaction of phenalenone and 1,2,3,4-tetrachlorocyclopentadiene. The gross structure of 5 has been determined by the X-ray analysis. The ground-state properties of 5were discussed from the spectroscopic data, dipole moment and bond lengths.     

The study and characterization of nucleosides by mass spectrometry—II: Comparisons between the mass spectra of 3′,5′-substituted,isomeric pairs of 2,2′-anhydrouridines

The mass spectra of 2,2′-anhydrouridines substituted in the 3′ and 5′ positions were studied. When the substituents were acetyl, pivaloyl, trifluoroacetyl or trimethylsilyl, it was found that specific fragmentations occured which could identify the position of the substituent. The specific fragmentations often resolve earlier ambiguities in the interpretation of mass spectra of 2,2′-anhydropyrimidine derivatives. Mono-acetyl and mono-pivaloyl 2,2′-anhydrouridines are not easily distinguished because of thermal reactions in the sample probe. They may be readily distinguished, however, by acetylation (with acetic anhydride-d₆ for the mono-acetyl isomers), trifluoroacetylation or trimethylsilylation, followed by mass spectral analysis of the reaction product.     

Dibromo(pyridoxal semicarbazone‐κ3N1,O3,O3′)copper(II)

The title compound, di­bromo(3‐hydroxy‐5‐hydroxy­methyl‐2‐methyl‐4‐pyridine­carbox­aldehyde semicarbazone‐κ³N¹,O³,O^3′)copper(II), [CuBr₂(C₉H₁₂N₄O₃)], consists of discrete complex units with the tridentate pyridoxal semicarbazone ligand as a zwitterion in an almost planar configuration. The Cu^II ions are in a distorted square‐pyramidal coordination, with the equatorial Br atom at a distance of 2.4017 (6) Å and the apical Br atom at a distance of 2.6860 (6) Å.     

Zur Kenntnis der Indolreaktion nach Fischer. II. Thermische und säurekatalysierte Indolisierung von 1′-Alkenyl-2′-methyl-2′-phenylacetohydraziden

On the Fischer-Indole Reaction. II. Thermal and Acid Catalysed Indolization of 1′-Alkenyl-2′-methyl-2′-phenylacetohydrazides Seven different 1′-alkenyl-2′-methyl-2′-phenylacetohydrazides, 6a-g , have been prepared by treatment of the methylphenylhydrazones 7 of appropriate ketones and aldehydes with acetyl chloride in pyridine. At 170° 6a-g are transformed into the N-methylindoles 3a-g and acetamide in moderate yield. N-Methylaniline is the other major reaction product indicating that homolytic cleavage of the weak N, N-bond in 6 is a major primary reaction step. It is likely but not proven that the N-methylindoles 3 are formed in a reaction sequence initiated by an uncatalysed concerted [3, 3]-sigmatropic rearrangement. Upon treatment of 6 with 0.5N dichloroacetic acid in anhydrous acetonitrile at room temperature a quantitative conversion to 3 is observed, interpreted as proceeding by a charge induced [3, 3]-sigmatropic rearrangement of protonated 6 in the rate determining step. The ketone derivatives 6a-e (R¹ = alkyl) react 40-1000 times faster with acid than the aldehyde derivatives 6f and 6g (R¹ = H). This is rationalized as a consequence of the increased basicity of 6a-e relative to 6f and 6g caused by a steric effect.     

Diaqua(oxydiacetato‐κ3O,O′,O′′)(pyridine‐3‐carboxamide‐κN1)copper(II)

In the mononuclear title compound, [Cu(C₄H₄O₅)(C₆H₆N₂O)(H₂O)₂], the Cu^II centre is bound to a chelating oxydiacetate ligand, a monodentate pyridine‐3‐carboxamide unit and two water molecules, defining an octahedral coordination where the first two ligands form the equatorial plane and the last two occupy the apical sites. The planar oxydiacetate ligand is slightly disordered at its central ether O atom. The availability of efficient donors and acceptors for hydrogen bonding results in a complex interaction scheme where each monomer links to six similar units to define a well connected three‐dimensional structure. A comparison is made with related structures in the literature, and the reasons for their differences are discussed.     

Carotinoide mit 7-Oxabicyclo[2.2.1]heptyl-Endgruppen. Teil I. Versuch einer Synthese von Cycloviolaxanthin (= (3S,5R,6R,3′S,5′R,6′R)-3,6:3′,6′-Diepoxy-5,6,5′,6′-tetrahydro-β,β-carotin-5,5′-diol)

Carotenoids with 7-Oxabicyclo[2,2.1]heptyl End Groups. Attempted Synthesis of Cycloviolaxanthin ( = (3S,5R,6S,3′S,5′R,6′R)-3,6:3′,6′- Diepoxy-5,6,5′,6′-tetrahydro-β,β-carotin-5,5′-diol) Starting from our recently described synthon (+)- 24 , the enantiomerically pure 3,6:4,5:3′,6′:4′,5′-tetraepoxy-4,5,4′,5′-tetrahydro-ε,ε-carotene ( 34 ) and its 15,15′-didehydro analogue 32 were synthesized in eleven and nine steps, respectively (Scheme 4). Chiroptical data show, in contrast to the parent ε,ε-carotene, a very weak interaction between the chiral centers at C(5), C(5′), C(6), C(6′), and the polyene system. Diisobutylaluminium hydride reduction of 32 lead rather than to the expected 15,15′-didehydro analogue 35 of Cycloviolaxanthin ( 8 ), to the polyenyne 36 (Scheme 5). We explain this reaction by an oxirane rearrangement leading to a cyclopropyl ether followed by a fragmentation to an aldehyd on the one side and an enol ether on the other (Scheme 6). This complex rearrangement includes a shift of the whole polyenyne chain from C(6), C(6′) to C(5), C(5′) of the original molecule.     

Studies on the synthesis of biphenylneolignans. Part 1: Enantioselective synthesis of (S,S)- and (R,R)-2,2′-dimethoxy-4-(3-hydroxy-1-propenyl)-4′-(1,2,3-trihydroxypropyl)diphenyl ether

Two erythro-isomers of 2,2′-dimethoxy-4-(3-hydroxy-1-propenyl)-4′-(1,2,3-trihydroxypropyl)diphenyl ether, (7′S, 8′S)-9 and (7′R, 8′R)-9, were synthesized in seven steps, in which an improved method for the synthesis of the key intermediate 3 was developed. The absolute configuration of the target molecules was also confirmed.     

Angiotensin-II Analogues. I: Synthesis and incorporation of the halogenated amino acids 3-(4′-iodophenyl)alanine, 3-(3′,5′-dibromo-4′-chlorophenyl)alanine, 3-(3′,4′,5′-tribromophenyl)alanine,and 3-(2′,3′,4′,5′,6′-pentabromophenyl)alanine

The synthesis of the polyhalogenated phenylalanines Phe(3′,4′,5′-Br₃) ( 3 ), Phe(3′,5′-Br₂-4′-Cl) ( 4 ) and DL -Phe (2′,3′,4′,5′,6′-Br₅) ( 9 ) is described. The trihalogenated phenylalanines 3 and 4 are obtained stereospecifically from Phe(4′-NH₂) by electrophilic bromination followed by Sandmeyer reaction. The most hydrophobic amino acid 9 is synthesized from pentabromobenzyl bromide and a glycine analogue by phase-transfer catalysis. With the amino acids 4, 9 , Phe(4′-I) and D -Phe, analogues of [1-sarcosin]angiotensin II ([Sar¹]AT) are produced for structure-activity studies and tritium incorporation. The diastereomeric pentabromo peptides L - and D - 13 are separated by HPLC. and identified by catalytic dehalogenation and comparison to [Sar¹]AT ( 10 ) and [Sar¹, D -Phe⁸]AT ( 14 ).     

Some reactions of 4-[(2′,3′-diphenyl-6′-methoxy-5′-benzofuranyl)-methylene]- and 4-[(2′,3′-diphenyl-5′-methoxy-6′-benzofuranyl)-methylene]-2-phenyloxazolin-5-one

2,3-Diphenyl-5-formyl-6-methoxybenzofuran was reacted with hippuric acid to give 4-[(2′,3′-diphenyl-6′-methoxy-5′-benzofuranyl)methylene]-2-phenyloxazolin-5-one. The above mentioned oxazolone yielded 2,3-diphenyl-6-methoxybenzofuranylacetic acid by reaction with hydrazine hydrate, nitrous acid, benzene followed by acid hydrolysis. The reactions of the oxazolone with hydroxylamine hydrochloride and primary or secondary amines were also investigated.     

5-(α-Fluorovinyl)tryptamines and 5-(α-Fluorovinyl)-3-(N-methyl-1′,2′,5′,6′,-tetrahydropyridin-3′- and -4′-yl)indoles—5-(α-Fluorovinyl)tryptamines

5-(α-Fluorovinyl)tryptamines 4a, 4b and 5-(α-fluorovinyl)-3-(N-methyl-1′,2′,5′,6′-tetrahydropyridin-3′- and -4′-yl) indoles 5a, 5b were synthesized using 5-(α-fluorovinyl)indole ( 7 ). The target compounds are bioisosteres of 5-carboxyamido substituted tryptamines and their tetrahydropyridyl analogs.     

Photochemical reactions of electron-deficient olefins with N,N,N′,N′-tetramethylbenzidine via photoinduced electron-transfer

Photoinduced electron transfer reactions of several electron-deficient olefins with N,N,N′,N′-tetramethylbenzidine (TMB) in acetonitrile solution have been studied by using laser flash photolysis technique and steady-state fluorescence quenching method. Laser pulse excitation of TMB yields ³TMB* after rapid intersystem crossing from ¹TMB*. The triplet which located at 480 nm is found to undergo fast quenching with the electron acceptors fumaronitrile (FN), dimethyl fumarate (DMF), diethyl fumarate (DEF), cinnamonitrile (CN), -acetoxyacrylonitrile (AAN), crotononitrile (CrN) and 3-methoxyacrylonitrile (MAN). Substituents binding to olefin molecule own different electron-donating/withdrawing powers, which determine the electron-deficient property (π-cloud density) of olefin molecule as well as control the electron transfer rate constant directly. The detection of ion radical intermediates in the photolysis reactions confirms the proposed electron transfer mechanism, as expected from thermodynamics. The quenching rate constants of triplet TMB by these olefins have been determined at 510 nm to avoid the disturbance of formed TMB cation radical around 475 nm. All the values approach or reach to the diffusion-controlled limit. In addition, fluorescence quenching rate constants have been also obtained by calculating with Stern–Volmer equation. A correlation between experimental electron transfer rate constants and free energy changes has been explained by Marcus theory of adiabatic outer-sphere electron transfer. Disharmonic k_q values for CN and CrN in endergonic region may be the disturbance of exciplexs formation.     

Saturated heterocycles. 242. Synthesis of 2-substituted-6-(6′,7′-dimethoxy-3′,4′-dihydro-1′-isoquinolyl)-5,6,7,8-tetrahydro- quinazolin-4(3H)-one Derivatives

In the reactions of the recently synthesized β-ketoesters 1-[(3′-methoxycarbonyl- and 1-[(3′-ethoxycarbonyl-4′-oxo)-1′-cyclohexyl]-3,4-dihydroisoquinoline 4, 5 with amidines or cyclic guanidines, a number of 2-substituted-6-(6′,7′-dimethoxy-3′,4′-dihydro-1′-isoquinolyl)-5,6,7,8-tetrahydroquinazolin-4(3H)-one derivatives 6–8 were prepared. The new compounds possess various pharmacological actions.