Γ-Lakton-cis-anellierung an Δ2- und Δ3- Cholesten

γ-Lactone-cis-annulation to Δ²- and Δ³- Cholestene. From Δ²- and Δ³- cholestene the γ-lactones 11a , 11b , 12a , and 12b are synthesized through the dibromocarbene adducts 3 and 4 , the bromohydrines 5 and 6 , the oxapiropentanes 7 and 8 , and the cyclobutanones 9a , 9b and 10a , 10b , respectively. The ¹³C-NMR.-spectra of 1–8 and 11 as well as the ORD.-spectra of the cyclobutanones 9 and 10 are reported.     

NMR spectra of Δ3- and Δ4-pyrrolin-2-one

The spectra of Δ³- and Δ⁴-pyrrolin-2-one were analysed and the sign of all the coupling constants determined by tickling and triple resonance experiments. A positive allylic interaction (J_xz in 2 ) is reported and four-bond couplings are discussed in particular. Deuterium exchange affords evidence for the tautomeric equilibrium between 1 and 2 .     

132. The Synthesis of Highly Strained Monocyclic and Bicyclic β-Lactams (Δ1-Carbapenem)

The synthesis of some β-lactams and one Δ¹-carbapenem is described. The electronic activation of monocyclic β-lactams of type 1 is not sufficient to generate a bioactive compound.     

Two pentadehydropeptides with different configurations of the ΔPhe residues

Comparison of the crystal structures of two pentadehydropeptides containing ΔPhe residues, namely (Z,Z)‐N‐(tert‐butoxycarbonyl)glycyl‐α,β‐phenylalanylglycyl‐α,β‐phenylalanylglycine (or Boc⁰–Gly¹–Δ^ZPhe²–Gly³–Δ^ZPhe⁴–Gly⁵–OH) methanol solvate, C₂₉H₃₃N₅O₈·CH₄O, (I), and (E,E)‐N‐(tert‐butoxycarbonyl)glycyl‐α,β‐phenylalanylglycyl‐α,β‐phenylalanylglycine (or Boc⁰–Gly¹–Δ^EPhe²–Gly³–Δ^EPhe⁴–Gly⁵–OH), C₂₉H₃₃N₅O₈, (II), indicates that the Δ^ZPhe residue is a more effective inducer of folded structures than the Δ^EPhe residue. The values of the torsion angles ϕ and ψ show the presence of two type‐III′β‐turns at the Δ^ZPhe residues and one type‐II β‐turn at the Δ^EPhe residue. All amino acids are linked trans to each other in both peptides. β‐Turns present in the peptides are stabilized by intramolecular 4→1 hydrogen bonds. Molecules in both structures form two‐dimensional hydrogen‐bond networks parallel to the (100) plane.     

Are the known Δ2-cephems inactive as antibiotics because of an unfavourable steric orientation of their 4α-carboxylic group? Synthesis and biology of two Δ2-cephem-4β-carboxylic acids

Two representatives of the yet unknown type of Δ²-cephem-4β-carboxylic acids were prepared. Contrarily to the prediction based on the activity model of Cohen, both acids proved inactive as antibiotics. Possible reasons for this discrepancy are briefly discussed.     

Photoinduced hydrogen abstraction‐coupling reaction mechanism of Δ5‐steroids with substituted 1, 4‐benzoquinones via electron transfer pathways

The photochemical reaction between three A⁵‐steroids (1–3) and a series of substituted 1,4‐benzoquinones and their mechanistic study were reported. The reaction in nitrogen atmosphere led to the formation of three products including the steroid‐quinone coupling compound (A), 7‐hydroxy derivatives of Δ⁵‐steroids (B) and substituted 1, 4‐hydroquinone (C). Both chemical and spectrometric evidences such as UV‐Visible spectra, ESR, chemically induced dynamic nuclear polarization (CIDNP) and cyclic voltammetry (CV) verified that the title reaction underwent a predominant photoinduced electron transfer pathway via the triplet quinone.     

Synthesis of Δ1[9]- and/or Δ8[9]-dehydroindolizidines and related compounds

A facile synthesis of Δ^1[9]- and/or Δ^8[9]-dehydroindolizidine and related compounds, consisting of dry distillation of γ-(N-2-piperidinonyl)butyric acid over soda-lime, is described. Reductions of these dehydroindolizidines and stereochemistry of 1-methylindolizidine are also described.     

Δ2‐Isoxazolines from β,γ‐unsaturated oximes

3,5‐Disubstituted Δ²‐isoxazolines can be prepared using the palladium‐mediated nucleometalation / methoxycarbonylation of β,γ‐unsaturated oximes. This novel route to this class of compounds is tolerant of a wide variety of functionality in the starting material, and provides a rapid route to highly functionalized isoxazolines.     

Asymmetric Synthesis of 2,4,5‐Trisubstituted Δ2‐Thiazolines

Δ²‐Thiazolines are interesting heterocycles that display a wide variety of biological characteristics. They are also common in chiral ligands used for asymmetric syntheses and as synthetic intermediates. Herein, we present asymmetric routes to 2,4,5‐trisubstituted Δ²‐thiazolines. These Δ²‐thiazolines were synthesized from readily accessible/commercially available α,β‐unsaturated methyl esters through a Sharpless asymmetric dihydroxylation and an O→N acyl migration reaction as key steps. The final products were obtained in good yields with up to 97 % enantiomeric excess.     

Novel synthesis of (−)-trans-Δ9,11-tetrahydrocannabinol

Addition of hydrogen chloride gas to a solution of Δ⁸-tetrahydrocannabinol in dry dichloromethane at -60° in the presence of zinc chloride results in the formation of a higher concentration of 9-α-chlorohexa-hydrocannabinol (75%) than the thermodynamically more stable 9-β-chlorohexahydrocannabinol (25%). The two isomers can be separated by reverse-phase hplc. Elimination of hydrogen chloride from 9-α-chlorohexa-hydrocannabinol using potassium t-amylate under anhydrous conditions gives exclusively Δ^9,11-tetrahydrocannabinol in overall yield of 65%.     

Chiral Bis(oxazoline) Ruthenium Complexes with Bipyridyl‐Type N‐Heteroaromatics: Comparative Stereochemical and Photochemical Characterization of their Λ‐ and Δ‐Diastereomeric Geminate Isomers

Diastereomeric geminate pairs of chiral bis(2‐oxazoline) ruthenium complexes with bipyridyl‐type N‐heteroaromatics, Λ‐ and Δ‐[Ru(L‐ L)₂(iPr‐biox)]²⁺ (iPr‐biox=(4S,4′S)‐4,4′‐diisopropyl‐2,2′‐bis(2‐oxazoline); L‐ L=2,2′‐bipyridyl (bpy) for 1 Λ and 1 Δ, 4,4′‐dimethyl‐2,2′‐bipyridyl (dmbpy) for 2 Λ and 2 Δ, and 1,10‐phenanthroline (phen) for 3 Λ and 3 Δ), were separated as BF₄ and PF₆ salts and were subjected to the comparative studies of their stereochemical and photochemical characterization. DFT calculations of 1 Λ and 1 Δ electronic configurations for the lowest triplet excited state revealed that their MO‐149 (HOMO) and MO‐150 (lower SOMO) characters are interchanged between them and that the phosphorescence‐emissive states are an admixture of a Ru‐to‐biox charge‐transfer state and an intraligand excited state within the iPr‐biox. Furthermore, photoluminescence properties of the two Λ,Δ‐diastereomeric series are discussed with reference to [Ru(bpy)₃]²⁺.     

Déplacements Chimiques Induits par Complexation à l'Europium en Série Δ1-Pyrazoline

The complex Eu (FOD)₃ is shown to be a convenient shift reagent for Δ¹-pyrazolines. The five examples described here were chosen to illustrate the usefulness of this method in the attribution of the stereochemistry of polycyclic Δ¹-pyrazolines.     

Microbial Transformation of (−)-Δ1-3,4-trans-Tetrahydrocannabinol by Cunninghamella blakesleeana LENDER

Incubation of (?)-Δ¹-3, 4-trans-tetrahydrocannabinol (= Δ¹-THC; 3 ) with stationary cultures of Cunninghamella blakesleeana LENDER (Zygomycetales) (ATCC 8688a) yielded a number of metabolic conversion products. Isolation and structure elucidation of 6α-hydroxy-Δ¹-THC ( 4 ), the potential psychoactive 3″-hydroxy-Δ¹-THC ( 2 ) and 4″-hydroxy-Δ¹-THC ( 1 ), and the hitherto unknown metabolites 4″-hydroxy-6-oxo-Δ¹-THC ( 5 ), 4″, 6α-dihydroxy-Δ¹-THC ( 7 ) and 4″, 7 -dihydroxy-Δ¹-THC ( 6 ) is described.     

Δ3- and Δ4-1,2,4-oxadiazolin-5- and 3-ones

Preparations for 2,3-diphenyl- and 2-benzyI-3-phenyl-Δ³-1,2,4-oxadiazolin-5-ones (3) and (4) and for 2,5-diphenyl-Δ⁴-1,2,4-oxadiazolin-3-one ( 7 ) are reported.     

Studies on Heterocyclic Colouring Matters Part II: Δ2,2′ -Bi (2H-1, 4-benzothiazines)

A novel one-step ‘Inverse Indigo Synthesis’ of the Δ^2,2′-bi(3,4-dihydro-3-oxo-2H-1, 4-benzothiazine) chromophore is described. Structure, substitution reactions, mechanism of formation, colour and other relevant properties of this system have been investigated in relation to known thioindigos. A synthesis of the basic skeleton of one of the ‘Trichosiderins’, the colouring matters of human red hair, is reported.     

Synthesis and Crystal Structure of meso-Δ,Λ-μ-Peroxo-μ-hydroxobis[bis(ethylenediamine)rhodium(III)]trifluoromethane Sulfonate

The reaction of the meso-diol, Δ,Λ-[(en)₂Rh(OH)₂Rh(en)₂]⁴⁺, with aqueous H₂O₂ and 1 equiv. of NaOH at 90° forms the μ-peroxo-μ-hydroxo-bridged species Δ,Λ-[(en)₂Rh(O₂,OH)Rh(en)₂]³⁺ in a yield of ca. 50%. The compound was crystallized as perchlorate and trifluoromethanesulfonate salts. The structure of the latter salt was determined by single-crystal X-ray diffraction. The crystals are triclinic with space group P1 and lattice constants a = 11.895(5), b = 12.491(4), c = 13.053(5) Å, α = 103.98(3), β = 92.59(3), γ = 119.52(6)°. The distances of the metal centres to the bridging peroxo ligand are 1.999(8) and 1.983(6) Å. The O? O distance in the peroxo group is 1.521(14) Å, and the dihedral angle of the Rh? O? O? Rh unit deviates 65° from planarity. The peroxo complex reacts reversibly with acid, and spectrophotometric studies suggest that the reaction involves protonation of the peroxo bridge, with pK_a = 2.70(2) at 25° in 1M NaClO₄.     

Mass spectra of substituted Δ2-1,2,4-oxadiazolines—I

The electron impact fragmentation of four Δ²-1,2,4-oxadiazolines with substituents at positions 3 and 5 has been examined. The direct analysis of daughter ions and high resolution mass measurements provided valuable information regarding certain ions. The present study clearly demonstrates that the substitution of phenyl or a substituted phenyl group for alkyl at C-3 and alkyl in place of a phenyl substituent at C-5 in the oxadiazoline system alters the fragmentation modes considerably.     

Elektrochemische Bildung von Δ1,2-Norbornen

Electrochemical Formation of Δ^1,2-Norbornene The electrochemical reduction of 1,2-dihalogen norbornanes in tetrahydrofuran/furan leads to a mixture of two isomeric cycloadducts 6 and 7. The ratio of these adducts corresponds to those which have been found in reductive bisdehalogenation of 1 and 2 by butyllithium.     

Determination of ΔH≠ and ΔS≠ by simultaneous 1H and 13C dynamic n.m.r. studies: Importance of the accuracy of temperature measurement

From ΔG_Tc^≠ values obtained by ¹H and ¹³C dynamic nuclear magnetic resonance studies of the same dynamic process, it is possible to estimate ΔH^≠ and ΔS^≠. Nevertheless, the accuracy of the temperature measurement is a factor which limits the applicability of this method. A very simple procedure for calibrating the usual temperature sensors is described, which can be applied to all types of n.m.r. probes. By the use of this procedure it is possible to measure coalescence temperatures in ¹H and ¹³C n.m.r. with such an accuracy that ΔS^≠ can be effectively determined from the difference between ΔG_Tc^≠ values.     

(Δ)[Fe(II)(phen)3]2+ Filled in the Chiral Cavitiy Constituted by {(Δ)[Fe(III)(C2O4)3](NH42+)(DMF)(H2O)32−}n

A chiral coordination compound {(Δ)[Fe(II)(phen)₃][(Δ)Fe(III)(C₂O₄)₃](NH₄)(H₂O)₃(DMF)}_n (phen = 1,10‐phenanthroline), (DMF = N,N'‐Dimethylformamide), has been synthesized, and the structure has been revealed by infrared spectroscopy and X‐ray single‐crystal diffraction. The framework consists of two chiral subunits. One subunit (Δ)[(Fe(III)(C₂O₄)₃]^3? which as host anion forms a chiral porous three‐dimensional supermolecular network with lattice water, lattice DMF and lattice ammonium cation through hydrogen bonds. And then the other is Δ[Fe(II)(phen)₃]²⁺ which as guest cation fills in the chiral cavity located in the previously mentioned host porous network.