Stereo‐Inversion in the (4R)‐γ‐Decanolactone Synthesis by Saccharomyces cerevisiae: (2E,4S)‐4‐Hydroxydec‐2‐enoic Acid Acts as a Key Intermediate

Methyl (2E,4R)‐4‐hydroxydec‐2‐enoate, methyl (2E,4S)‐4‐hydroxydec‐2‐enoate, and ethyl (±)‐(2E)‐4‐hydroxy[4‐²H]dec‐2‐enoate were chemically synthesized and incubated in the yeast Saccharomyces cerevisiae. Initial C‐chain elongation of these substrates to C₁₂ and, to a lesser extent, C₁₄ fatty acids was observed, followed by γ‐decanolactone formation. Metabolic conversion of methyl (2E,4R)‐4‐hydroxydec‐2‐enoate and methyl (2E,4S)‐4‐hydroxydec‐2‐enoate both led to (4R)‐γ‐decanolactone with >99% ee and 80% ee, respectively. Biotransformation of ethyl (±)‐(2E)‐4‐hydroxy(4‐²H)dec‐2‐enoate yielded (4R)‐γ‐[²H]decanolactone with 61% of the ²H label maintained and in 90% ee indicating a stereoinversion pathway. Electron‐impact mass spectrometry analysis (Fig. 4) of 4‐hydroxydecanoic acid indicated a partial C(4)→C(2) ²H shift. The formation of erythro‐3,4‐dihydroxydecanoic acid and erythro‐3‐hydroxy‐γ‐decanolactone from methyl (2E,4S)‐4‐hydroxydec‐2‐enoate supports a net inversion to (4R)‐γ‐decanolactone via 4‐oxodecanoic acid. As postulated in a previous work, (2E,4S)‐4‐hydroxydec‐2‐enoic acid was shown to be a key intermediate during (4R)‐γ‐decanolactone formation via degradation of (3S,4S)‐dihydroxy fatty acids and precursors by Saccharomyces cerevisiae.     

Synthesis of the (2<Emphasis Type="Italic">S</Emphasis>,4<Emphasis Type="Italic">S</Emphasis>)-stereoisomers of 4-(indol-1-yl) and 4-arylamino derivatives of 5-oxoproline,proline, and 2-hydroxymethylpyrrolidine

Nucleophilic substitution of the halogen atom in dimethyl (S)-4-bromoglutamate followed by removal of the protecting groups and closure of a lactam ring afforded (2S,4S)-4-(indolin-1-yl)-5-oxoproline. The indoline fragment was oxidized into the indole fragment to give (2S,4S)-4-(indol-1-yl)-5-oxoproline; reduction of the carbonyl groups with BH3 yielded (2S,4S)-4-(indol-1-yl)prolines and (2S,4S)-2-hydroxymethyl-4-(indol-1-yl)pyrrolidines. Reduction of (2S,4S)-4-arylamino-5-oxoprolines with BH3 to the corresponding (2S,4S)-4-arylaminoprolines and (2S,4S)-4-arylamino-2-hydroxymethylpyrrolidines was studied.     

Straightforward Preparation of (2E,4Z)-2,4-Heptadien-1-ol and (2E,4Z)-2,4-Heptadienal

Abstract

A concise synthesis of (2E,4Z)-2,4-heptadien-1-ol and (2E,4Z)-2,4-heptadienal is presented. Commercially available (Z)-2-penten-1-ol was converted to ethyl-(2E,4Z)-2,4-heptadienoate by reaction with activated MnO₂ and (carboethoxymethylene)triphenylphosphorane in the presence of benzoic acid as a catalyst. Ethyl-(2E,4Z)-2,4-heptadienoate was converted to (2E,4Z)-2,4-heptadien-1-ol with LiAlH₄. The alcohol was partially oxidized to (2E,4Z)-2,4-heptadienal with MnO₂. The title compounds are male-specific, antennally active volatile compounds from the Saltcedar leaf beetle, Diorhabda elongata Brulle (Coleoptera: Chrysomelidae) and have potential use in the biological control of the invasive weed saltcedar (Tamarix spp).     

Metabolism of Deuterated threo‐Dihydroxy Fatty Acids in Saccharomyces cerevisiae: Enantioselective Formation and Characterization of Hydroxylactones and γ‐Lactones

Biotransformation of (±)‐threo‐7,8‐dihydroxy(7,8‐²H₂)tetradecanoic acids (threo‐(7,8‐²H₂)‐ 3 ) in Saccharomyces cerevisiae afforded 5,6‐dihydroxy(5,6‐²H₂)dodecanoic acids (threo‐(5,6‐²H₂)‐ 4 ), which were converted to (5S,6S)‐6‐hydroxy(5,6‐²H₂)dodecano‐5‐lactone ((5S,6S)‐(5,6‐²H₂)‐ 7 ) with 80% e.e. and (5S,6S)‐5‐hydroxy(5,6‐²H₂)dodecano‐6‐lactone ((5S,6S)‐5,6‐²H₂)‐ 8 ). Further β‐oxidation of threo‐(5,6‐²H₂)‐ 4 yielded 3,4‐dihydroxy(3,4‐²H₂)decanoic acids (threo‐(3,4‐²H₂)‐ 5 ), which were converted to (3R,4R)‐3‐hydroxy(3,4‐²H₂)decano‐4‐lactone ((3R,4R)‐ 9 ) with 44% e.e. and converted to ²H‐labeled decano‐4‐lactones ((4R)‐(3‐²H₁)‐ and (4R)‐(2,3‐²H₂)‐ 6 ) with 96% e.e. These results were confirmed by experiments in which (±)‐threo‐3,4‐dihydroxy(3,4‐²H₂)decanoic acids (threo‐(3,4‐²H₂)‐ 5 ) were incubated with yeast. From incubations of methyl (5S,6S)‐ and (5R,6R)‐5,6‐dihydroxy(5,6‐²H₂)dodecanoates ((5S,6S)‐ and (5R,6R)‐(5,6‐²H₂)‐ 4a ), the (5S,6S)‐enantiomer was identified as the precursor of (4R)‐(3‐²H₁)‐ and (2,3‐²H₂)‐ 6 ). Therefore, (4R)‐ 6 is synthesized from (3S,4S)‐ 5 by an oxidation/keto acid reduction pathway involving hydrogen transfer from C(4) to C(2). In an analogous experiment, methyl (9S,10S)‐9,10‐dihydroxyoctadecanoate ((9S,10S)‐ 10a ) was metabolized to (3S,4S)‐3,4‐dihydroxydodecanoic acid ((3S,4S)‐ 15 ) and converted to (4R)‐dodecano‐4‐lactone ((4R)‐ 18 ).     

Syntheses,Crystal Structures and Properties of the Tetrametaphosphimates MII2(PO2NH)4 · 8 H2O with MII = Mg,Mn, Co and Zn

Mg₂(PO₂NH)₄ · 8 H₂O ( 1 ), Mn₂(PO₂NH)₄ · 8 H₂O ( 2 ), Co₂(PO₂NH)₄ · 8 H₂O ( 3 ) and Zn₂(PO₂NH)₄ · 8 H₂O ( 4 ) were obtained as microcrystalline powders by combining aqueous solutions of K₄(PO₂NH)₄ · 4 H₂O and MX₂ · y H₂O (M = Mg, Mn, Co, Zn; X = Cl, NO₃). Single crystals were obtained by crystallization in gelatine gels in U‐tubes or test‐tubes. 2 and 4 were characterized by thermogravimetry and 4 was additionally characterized by temperature dependend in situ powder diffractometry. The structures of 1 , 2 , 3 and 4 were found to be isotypic and were solved by single‐crystal X‐ray methods: P 2₁/c, Z = 2 ( 1 : a = 645.4(2), b = 1050.1(2), c = 1283.3(3) pm, β = 104.66(3)°; 2 : a = 648.7(2), b = 1063.1(2), c = 1310.8(3) pm, β = 103.93(3)°; 3 : a = 643.3(2), b = 1049.0(2), c = 1286.7(3) pm, β = 104.28(3)°; 4 : a = 644.18(5), b = 1049.22(7), c = 1282.43(8) pm, β = 104.122(6)°). The structure is composed of MO₆ octahedra and (PO₂NH)₄^4— anions. The P₄N₄ rings of the (PO₂NH)₄^4— anions exhibit a slightly distorted chair conformation, which is supported by IR data and has been described by torsion angles, Displacement Asymmetry Parameters and Puckering Parameters. Via M²⁺ ions and hydrogen bonds, the tetrametaphosphimate anions are connected forming layers perpendicular to [100]. These layers are connected by hydrogen bonds.     

Trifluoromethyl Sulfones and Perfluoroalkanesulfonamides of the Azole Series

2-Phenyl-4-trifluoromethylsulfonylmethyl-2H-1,2,3-triazole was synthesized from 4-bromo-methyl-2-phenyl-2H-1,2,3-triazole and sodium trifluoromethanesulfinate CF₃SO₂Na. 1(2)-Ethyl-4-nitro-1(2)H-1,2,3-triazoles and 4-nitro-2-phenyl-2H-1,2,3-triazole were reduced to the corresponding amines. Intermediate 1,2-bis(1-ethyl-1H-1,2,3-triazol-4-yl)diazene 1-oxide exists as a mixture of syn and anti isomers, the former being stabilized via formation of a strong intramolecular hydrogen bond. The reduction of 2-ethyl-4-nitro-2H-1,2,3-triazole in the presence of HCl afforded the target 4-amino-2-ethyl-2H-1,2,3-triazole and also 4-amino-5-chloro-2-ethyl-2H-1,2,3-triazole. Treatment of alkyl-substituted 4-amino-1,2,3-triazoles with trifluoromethanesulfonyl chloride and pentafluoroethanesulfonyl chloride gave N-triazolyl-substituted trifluoromethane- and pentafluoroethanesulfonamides and -imides.     

Tetrameric indium trichloride,a new modification of a widely used compound

The title compound, hexa‐μ‐chloro‐1:2κ⁴Cl;2:3κ⁴Cl;3:4κ⁴Cl‐hexachloro‐1κ²Cl,2κCl,3κCl,4κ²Cl‐hexakis­(diethyl­amine)‐1κ²N,2κN,3κN,4κ²N‐tetraindium(III), [(InCl₃)₄(Et₂NH)₆] or [In₄Cl₁₂(C₄H₁₁N)₆], lies about an inversion centre and consists of four octahedrally coordinated In centres linked by bridging Cl atoms to form three four‐membered In₂Cl₂ rings.     

Monomer-isomerization polymerization. XVIII. Monomer-isomerization copolymerizations of 4-phenyl-2-butene with 4-methyl-2-pentene and 3-heptene with Ziegler-Natta catalyst

4-Phenyl-2-butene (4Ph2B) undergoes monomer-isomerization copolymerization with 4-methyl-2-pentene (4M2P) and 2-and 3-heptene (2H and 3H) with TiCl₃–(C₂H₅)₃Al catalyst at 80°C to produce copolymer consisting exclusively of 1-olefin units. For comparison the copolymerization of 4-phenyl-1-butene (4Ph1B) with 4-methyl-1-pentene (4M1P) and 1-heptene (1H) was carried out under similar conditions. The composition of the copolymers obtained from these copolymerizations was determined from the ratios of optical densities D₁₃₈₀ and D₁₆₀₀ of infrared (IR) spectra of their thin films. The apparent monomer reactivity ratios for the monomer-isomerization copolymerization of 4Ph2B with 4M2P, 2H, and 3H in which the concentration of olefin monomer in the feed was used as internal olefin and those for the copolymerization of 4Ph1B with 4M1P and 1H were determined as follows: 4Ph2B(M₁)-4M2P(M₂); r₁ = 0.90, r₂ = 0.20, 4Ph1B(M₁)-4M1P (M₂); r₁ = 0.40, r₂ = 0.70, 4Ph2B(M₁)-2H(M₂); r₁, = 0.45, r₂ = 1.85, 4Ph2B(M₁)-3H(M₂); r₁ = 0.50, r₂ = 1.20, 4Ph1B(M₁)-1H(M₂); r₁ = 0.55, r₂ = 0.75. The difference in monomer reactivity ratios seemed to originate from the rate of isomerization from 2- or 3-olefins to 1-oletins in these monomer-isomerization copolymerizations.     

Influence of the Coordination of Donor Solvent Molecules to 1,4,7,10-Tetramethyl-1,4,7,10- tetraazacyclododecanenickel(II) and Analogous Nickel(II) Complexes on Their Steric Factors

Coordination equilibrium constants (K _NiS) of some donor solvent molecules to 1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecanenickel(II) ([Ni(Me₄[12]aneN₄)]²⁺) were determined in nitrobenzene (a noncoordinating bulk solvent). The first (K _NiS1) and second stepwise coordination equilibrium constants (K _NiS2) for 1,4,7,10-tetraazacyclododecanenickel(II) ([Ni([12]aneN₄)]²⁺), 1,4,8,11-tetraazac yclotetradecane- nickel(II) ([Ni([14] aneN₄)]²⁺), 1,4,8,11-tetrathiacyclotetra-decanenickel(II) ([Ni([14]aneS₄)]²⁺) were also reinvestigated. The K _NiS values for [Ni(Me₄[12]aneN₄)]²⁺ were compared to those of [Ni([12]aneN₄)]²⁺, (1R,4S, 8R,11S)-1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecanenickel(II) (R,S,R,S-[Ni(Me₄[14]aneN₄)]²⁺), R,R,S,S-[Ni(Me₄[14]aneN₄)]²⁺, [Ni([14]aneN₄)]²⁺, and [Ni([14]aneS₄)]²⁺. Coordination of pyridine (Py), N,N,N′,N′-tetramethylurea (TMU), and N,N-dimethylacetamide (DMA) to [Ni(Me₄[12]aneN₄)]²⁺ was observed, although these donor solvent molecules did not coordinate to R,S,R,S-[Ni(Me₄[14]aneN₄)]²⁺. The K _NiS values for Py, TMU, and DMA are 7.9, 2.8, and 9.0 dm³⋅mol⁻¹, respectively. Some hydrogen-bonding waters were coordinated to R,S,R,S-[Ni(Me₄[14]aneN₄)]²⁺, but such waters did not coordinate to [Ni(Me₄[12] aneN₄)]²⁺. Also, the K _NiS2 values were larger than the corresponding K _NiS1 values for [Ni([14]aneS₄)]²⁺. Furthermore, the K _NiS1 values for [Ni([12]aneN₄)]²⁺ were the largest among these nickel(II) complex cations. The K _NiS, K _NiS1, and K _NiS2 values are discussed in terms of properties of the donor solvents and steric strains of these nickel(II) complex cations.     

4-Acyl-2H-thiopyran-3,5(4H,6H)-diones: Synthesis,Oxidation, and Reaction with Amines

Acylation of 2H-thiopyran-3,5(4H,6H)-dione and 2-methyl-2H-thiopyran-3,5(4H,6H)-dione with acetyl chloride or propionyl chloride afforded the corresponding 4-acyl-2H-thiopyran-3,5(4H,6H)-diones. Oxidation of 4-acetyl-2H-thiopyran-3,5(4H,6H)-dione with m-chloroperoxybenzoic acid gave 4-acetyl-2H-thiopyran-3,5(4H,6H)-dione 1-oxide. 4-Acyl-2H-thiopyran-3,5(4H,6H)-diones and 4-acetyl-2H-thiopyran-3,5(4H,6H)-dione 1-oxide reacted with pyrrolidine, allylamine, and p-anisidine, resulting in formation of the corresponding 4-aminomethylene derivatives.     

Epimerization at C-2 of 2-substituted thiazolidine-4-carboxylic acids

2(R,S)-5,5-Trimethylthiazolidine-4-(S)-carboxylic acid ( 1a ), with a 3.3 to 1 predominance of the 2S (cis) isomer, was shown to epimerize at the C-2 position in neutral, protic solvents. This was manifested by mutarotation concomitant to changes in the ratios of the C-4 methine proton resonances in the nmr spectrum. Compound 1a was stable in dilute sodium carbonate solution, but underwent rapid equilibration in 1N hydrochloric acid. Acetylation of 1a gave an acetyl derivative ( 2a ) with exclusively 2S,4S stereochemistry. Chiral integrity at C-2 was proved by conversion of both 2a and its enantiomer 2b via their munchnone derivatives to enantiomeric dimethyl 1,1,3,5-tetramethyl-1H,2H-pyrrolo[1,2-c]thiazole-6,7-dicarboxylates ( 4a and 4b ). Acetylation of 2-(R,S)-phenyl-5,5-dimethylthiazolidine-4(S)-carboxylic acid, afforded both the 2 S ,4S ( 6a ) and 2R,4S ( 6b ) epimers. Epimerization of 6a at C-4 gave the 2S,4R isomer ( 6c ) which was enantiomeric with 6b .     

Syntheses for 2-amino and 2-mercapto-2H-1,4-benzoxazin-3(4H)-one and 2H-1,4-benzothiazin-3(4H)-one as aza and thio analogues of the natural product blepharigenin

2-Amino-2H-1,4-benzoxazin-3(4H)-one 3 , 2-amino-2H-1,4-benzothiazin-3(4H)-one 4 , 2-mercapto-2H-1,4-benzoxazin-3(4H)-one 7 , and 2-mercapto-2H-1,4-benzothiazin-3(4H)-one 8 representing aza and thio analogues of the natural product's aglucone Blepharigenin (2-hydroxy-2H-1,4-benzoxazin-3(4H)-one) from Gramineae and Acantnaceae species have been synthesized for the first time from their 2-bromo precursors 1 and 2 . Attempts to similarly prepare the 4-hydroxy derivatives of 7 and 8 , which would represent new thio analogues of the naturally occurring cyclic hydroxamic acid, 2,4-dihydroxy-2H-1,4-benzoxazin-3(4H)-one, have failed.     

Multigram Solution‐Phase Synthesis of Three Diastereomeric Tripeptidic Second‐Generation Dendrons Based on (2S,4S)‐, (2S,4R)‐, and (2R,4S)‐4‐Aminoprolines

Three diastereomeric second‐generation (G2) dendrons were prepared by using (2S,4S)‐, (2S,4R)‐, and (2R,4S)‐4‐aminoprolines on the multigram scale with highly optimized and fully reproducible solution‐phase methods. The peripheral 4‐aminoproline branching units of all the dendrons have the 2S,4S configuration throughout, whereas those units at the focal point have the 2S,4S, 2S,4R, and 2R,4S configurations. These latter configurations led to the dendrons being named (2S,4S)‐ 1 , (2S,4R)‐ 1 , and (2R,4S)‐ 1 , respectively. The 4‐aminoproline derivatives used in this study are new, although many closely related compounds exist. Their syntheses were optimized. The dendron assembly involved amide coupling, the efficiency of which was also optimized by employing the following well‐known reagents: EDC/HOBt, DCC/HOSu, TBTA/HOBt, TBTU/HOBt, BOP/HOBt, pentafluorophenol, and PyBOP/HOBt. It was found that the use of PyBOP is by far the best for dendrons (2S,4S)‐ 1 and (2R,4S)‐ 1 , and pentafluorophenol active ester is best for (2S,4R)‐ 1 . Because of their multigram scale, all couplings were done in solution instead of by solid‐phase procedures. Purifications were, nevertheless, easy. The optical purities of the key intermediates as well as the three G2 dendrons were analyzed by chiral HPLC analysis. These novel, diastereomeric second‐generation dendrons have a rather compact and conformationally highly rigid structure that makes them interesting candidates for applications, for example, in the field of dendronized polymers and in organocatalysis.     

A Novel 2H‐Azirin‐3‐amine as a Dipeptide (Aib‐Hyp) Synthon

The synthesis of methyl (2S,4R)‐4‐(benzyloxy)‐N‐(2,2‐dimethyl‐2H‐azirin‐3‐yl)prolinate ( 10 ), a novel 2H‐azirin‐3‐amine (`3‐amino‐2H‐azirine'), is described (Scheme 1). The reaction of methyl (2S,4R)‐N‐(2‐methylpropanoyl)‐4‐(benzyloxy)prolinate ( 7 ) with Lawesson reagent gave methyl (2S,4R)‐4‐(benzyloxy)‐N‐[2‐(methylthio)propanoyl]prolinate ( 8 ) and consecutive treatment with COCl₂, 1,4‐diazabicyclo[2.2.2]octane (DABCO), and NaN₃ led to 10 . The use of 10 as a building block of the dipeptide Aib‐Hyp (Aib=2‐aminoisobutyric acid, Hyp=(2S,4R)‐4‐hydroxyproline) is demonstrated by the syntheses of several model peptides (Scheme 2 and Table). The benzyl protecting group of the 4‐OH function in Hyp in the model peptides has been removed in good yields.     

2-Trif luoromethyl-4H-thiochromen-4-one and 2-trif luoromethyl-4H-thiochromene-4-thione: Synthesis and reactivities

2-Trifluoromethyl-4H-thiochromene-4-thione obtained from 2-trifluoromethyl-4H-thiochromen-4-one and P₂S₅ reacts with aromatic amines, hydrazine hydrate, phenylhydrazine, and hydroxylamine at the C(4) atom of the chromene ring to give the corresponding anils, azine, hydrazones, and oxime of thiochromone. 2-Trifluoromethyl-4H-thiochromen-4-one is oxidized by hydrogen peroxide in AcOH into 4-oxo-2-trifluoromethyl-4H-thiochromene 1,1-dioxide and reduced by NaBH₄ to 2-trifluoromethyl-4H-thiochromen-4-ol or cis-2-(trifluoromethyl)thiochroman-4-ol. When treated with hydrazine hydrate, thiochromen-4-one gives 3(5)-(2-mercaptophenyl)-5(3)-trifluoromethylpyrazole. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 504–509, March, 2006.     

Stereochemistry of [4 + 2] Cycloadditions of Perfluorinated Selenocarbonyls to 1, 3‐Dienes

In completely stereospecific [4+2] cycloadditions, the perfluorinated selenocarbonyls 1 and 2 react both with trans‐trans‐2, 4‐hexadiene and cis‐trans‐2, 4‐hexadiene to yield 3, 6‐dihydro‐cis‐3, 6‐dimethyl‐2H‐selenapyrans 3 , 4a and 4b . The observed stereoselectivity leads to the conclusion, that the [4+2] cycloaddition of perfluorinated selenocarbonyls follows a concerted pathway. An identical mixture of isomers was isolated when using the precursor for 2 , trimethylstannyl (pentafluoroethyl)selane, which reacts with both 1, 3‐dienes over several weeks to form a mixture of syn‐2‐fluoro‐3, 6‐dihydro‐cis‐3, 6‐dimethyl‐2‐trifluoromethyl‐2H‐selenapyran ( 4a ) and anti‐2‐fluoro‐3, 6‐dihydro‐cis‐3, 6‐dimethyl‐2‐trifluoromethyl‐2H‐selenapyran ( 4b ) in the same ratio as found for 2 , thus proving the intermediate formation of Se=C(F)CF₃ ( 2 ). Complex 2D NMR experiments were used to distinguish the isomers 4a and 4b and to assign the ¹H, ¹³C and ¹⁹F NMR data of the selenaheterocycles.     

Breaking the Mirror: pH‐Controlled Chirality Generation from a meso Ligand to a Racemic Ligand

To study the conversion from a meso form to a racemic form of tetrahydrofurantetracarboxylic acid (H₄L), seven novel coordination polymers were synthesized by the hydrothermal reaction of Zn(NO₃)₂ ? 6 H₂O with (2S,3S,4R,5R)‐H₄L in the presence of 1,10‐phenanthroline (phen), 2,2′‐bipyridine (2,2′‐bpy), or 4,4′‐bipyridine (4,4′‐bpy): [Zn₂{(2S,3S,4R,5R)‐L}(phen)₂(H₂O)] ? 2 H₂O ( 1 ), [Zn₄{(2S,3R,4R,5R)‐L}{(2S,3S,4S,5R)‐L}(phen)₂(H₂O)₂] ( 2 ), [Zn₂{(2S,3S,4R,5R)‐L}(H₂O)₂] ? H₂O ( 3 ), [Zn₄{(2S,3R,4R,5R)‐L}{(2S,3S,4S,5R)‐L} (2,2′‐bpy)₂(H₂O)₂] ? 2 H₂O ( 4 ), [Zn₂ {(2S,3S,4R,5R)‐L}(2,2′‐bpy)(H₂O)] ( 5 ), [Zn₄{(2S,3R,4R,5R)‐L}{(2S,3S,4S,5R)‐L} (4,4′‐bpy)₂(H₂O)₂] ( 6 ), and [Zn₂ {(2S,3S,4R,5R)‐L}(4,4′‐bpy)(H₂O)] ? 2 H₂O ( 7 ). These complexes were obtained by control of the pH values of reaction mixtures, with an initial of pH 2.0 for 1 , 2.5 for 2 , 4 , and 6 , and 4.5 for 3 , 5 , and 7 , respectively. The expected configuration conversion has been successfully realized during the formation of 2 , 4 , and 6 , and the enantiomers of L, (2S,3R,4R,5R)‐L and (2S,3S,4S,5R)‐L, are trapped in them, whereas L ligands in the other four complexes retain the original meso form, which indicates that such a conversion is possibly pH controlled. Acid‐catalyzed enol–keto tautomerism has been introduced to explain the mechanism of this conversion. Complex 1 features a simple 1D metal–L chain that is extended into a 3D supramolecular structure by π–π packing interactions between phen ligands and hydrogen bonds. Complex 2 has 2D racemic layers that consist of centrosymmetric bimetallic units, and a final 3D supramolecular framework is formed by the interlinking of these layers through π–π packing interactions of phen. Complex 3 is a 3D metal–organic framework (MOF) involving meso‐L ligands, which can be regarded as (4,6)‐connected nets with vertex symbol (4⁵.6)(4⁷.6⁸). Complexes 4 and 5 contain 2D racemic layers and (6,3)‐honeycomb layers, respectively, both of which are combined into 3D supramolecular structures through π–π packing interactions of 2,2′‐bpy. The structure of complex 6 is a 2D network formed by 4,4′‐bpy bridging 1D tubes, which consist of metal atoms and enantiomers of L. These layers are connected through hydrogen bonds to give the final 3D porous supramolecular framework of 6 . Complex 7 is a 3D MOF with novel (3,4,5)‐connected (6³)(4².6⁴)(4².6⁶.8²) topology. The thermal stability of these compounds was also investigated.     

Generation and reactivity of 3‐carbethoxy‐5‐phenyl‐5H,7H‐thiazolo[3,4‐c]oxazol‐4‐ium‐1‐olate

3‐Carbethoxy‐5‐phenyl‐5H,7H‐thiazolo[3,4‐c]oxazol‐4‐ium‐1‐olate was generated from (2R,4R)‐N‐ethoxyoxalyl‐2‐phenylthiazolidine‐4‐carboxylic acid and its reactivity studied. This münchnone showed low reactivity as dipole although from the reaction with dimethyl acetylenedicarboxylate the corresponding (3R)‐3‐phenyl‐17H,3H‐pyrrolo[1,2‐c]thiazole‐5,6,7‐tricarboxylate could be isolated. The thermolysis of (2R,4R)‐N‐ethoxyoxalyl‐2‐phenylthiazolidine‐4‐carboxylic acid in refluxing acetic anhydride led to the synthesis of N‐(1‐ethoxycarbonyl‐2‐phenylvinyl)‐2‐phenyl‐4‐thioxo‐1,3‐thiazolidine. The structure of methyl (2R,4R)‐N‐ethoxyoxalyl‐2‐phenylthiazoliddine‐4‐carboxylate was determined by X‐ray crystallography.     

Synthesis of 4H-pyrazolo- and 4H-pyrrolophenothiazin-4-one derivatives

5-Methyl- and 6-methyl-2-phenyl-2H-indazole-4,7-diones were condensed with 2-aminobenzenethiol or 6-substituted-3-aminopyridine-2(1H)thiones 4 to produce a new type of 5-methyl-2-phenyl-4H-pyrazolophenothiazin-4-ones or 8-substituted-7-aza-5-methyl-2-phenyl-4H-pyrazolophenothiazin-4-one derivatives. From 6-bromo-2,5-dimethyl-1,3-diphenyl-2H-isoindole-4,7-dione and 4 8-substituted-7-aza-2,5-dimethyl-1,3-diphenyl-4H-pyrrolophenothiazin-4-one derivatives were also prepared.     

Synthesis of 3-aminothiophene-2-thioamides

Summary 4-Dimethylamino-5,6-dihydro-2H-thiopyran-2-thiones (1) were alkylated to N,N-dimethyl-6-methylthio-2H-thiopyran-4(3H)-iminiumiodides (2). Aminolysis of the latter with ammonia led to 6-dimethylamino-2H-thiopyran-4(3H)-iminiumiodides (3) which were hydrolyzed to 3-amino-N,N-dimethyl-2,4-pentadienthioamides (4). Ring closure with sulfur gave 3-aminothiophene-2-thioamides (5). The configurations of the pentadienthioamides (4) have been investigated by NOE experiments. The structures of the thiophene-2-thioamides (5) were established by means of two-dimensional NMR techniques.

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Synthese von 3-Aminothiophen-2-thiocarboxamiden

Zusammenfassung 4-Dimethylamino-5,6-dihydro-2H-thiopyran-2-thione (1) wurden zu N,N-Dimethyl-6-methylthio-2H-thiopyran-4(3H)-iminiumiodiden(2) alkyliert. Die Umsetzung mit Ammoniak führte zur Bildung von 6-Dimethylamino-2H-thiopyran-4(3H)-iminiumiodiden (3). Diese wurden zu 3-Amino-N,N-dimethyl-2,4-pentadienthioamiden (4) hydrolysiert. Beim Erhitzen mit Schwefel erfolgte Cyclisierung zu 3-Aminothiophen-2-thiocarboxamiden (5). Die Konfiguration der Pentadienthioamide (4) wurde mit NOE-Messungen untersucht, die der Thiophen-2-thiocarboxamide (5) mit Hilfe zweidimensionaler NMR-Methoden aufgeklärt.