9‐Ethyl‐1,4‐dimethyl‐6‐(4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolan‐2‐yl)‐9H‐carbazole and 6‐bromo‐9‐ethyl‐1,4‐dimethyl‐9H‐carbazole

The title carbazolyl boronic ester, C₂₂H₂₈BNO₂, (I), is a building block for the synthesis of new carbazole derivatives of potential utility as pharmaceutically active compounds. The crystal structure of (I) and of the title bromocarbazole compound, C₁₆H₁₆BrN, (II), the synthetic precursor of (I), were solved and analysed with the aim of understanding the lack of reactivity of (I) under Suzuki cross‐coupling reaction conditions. In both structures, the methyl groups are coplanar with the carbazole ring system, and the ethyl group lies out of the carbazole plane. The dioxaborolane ring of boronic ester (I) adopts a half‐chair conformation but lies approximately in a planar orientation with respect of the carbazole ring system, whereas the Br atom of (II) is coplanar with the carbazole plane. In (I), the carbazole–boronic ester C—B bond length is 1.5435 (14) Å, which is somewhat shorter than the usual value of 1.57 Å.     

O‐Benzyl‐N‐tert‐butoxy­carbonyl‐N‐methyl‐l‐tyrosine

The crystal structure of the title compound, alternatively called 3‐[4‐(benzyl­oxy)­phenyl]‐2‐(N‐tert‐butoxy­car­bonyl‐N‐methyl­amino)­propi­onic acid, C₂₂H₂₇NO₅, has been studied in order to ex­amine the role of N‐methyl­ation as a determinant of peptide conformation. The conformation of the tert‐butoxy­carbonyl group is trans–trans. The side chain has a folded conformation and the two phenyl rings are effectively perpendicular to one another. The carboxyl­ate hydroxyl group and the urethane carbonyl group form a strong intermolecular O—H?O hydrogen bond.     

The peptide Z‐Aib‐Aib‐Aib‐L‐Ala‐OtBu

The title peptide, N‐benzyloxycarbonyl‐α‐aminoisobutyryl‐α‐aminoisobutyryl‐α‐aminoisobutyryl‐L‐alanine tert‐butyl ester or Z‐Aib‐Aib‐Aib‐L‐Ala‐OtBu (Aib is α‐aminoisobutyric acid, Z is benzyloxycarbonyl and OtBu indicates the tert‐butyl ester), C₂₇H₄₂N₄O₇, is a left‐handed helix with a right‐handed conformation in the fourth residue, which is the only chiral residue. There are two 4→1 intramolecular hydrogen bonds in the structure. In the lattice, molecules are hydrogen bonded to form columns along the c axis.     

4‐Acetonyl­idene‐1‐ethyl‐2,3,4,5‐tetra­hydro‐1H‐1,5‐benzodiazepin‐2‐one

The title compound, C₁₄H₁₆N₂O₂, contains a diazepine ring, which appears in a boat conformation. An intramolecular hydrogen bond is formed between the NH group of the diazepine ring and a carbonyl O atom of one of the side chains.     

4‐Acetyl‐5‐methyl‐2‐phenyl‐1,2‐di­hydro‐3H‐pyrazol‐3‐one hydrate

The title compound, C₁₂H₁₂O₂N₂·H₂O, is described. Although the keto–enol form of the ligand in solution is known, the compound crystallized in the orthorhombic space group P2₁2₁2₁ with only the monohydrated 1,3‐diketo form. The intermolecular hydrogen bond between the imino N—H group of the ligand and O atom of the water mol­ecule recorded an H?O distance of 1.73 (3) Å.     

p‐Cresyl 2,3‐an­hydro‐5‐deoxy‐5‐phthal­imido‐1‐thio‐α‐d‐lyxo­furan­oside

The crystal structure of the title compound, C₂₀H₁₇NO₄S, (I), was determined in order to compare the solution and solid‐state conformations. The mol­ecule was synthesized as a building block for incorporation into oligosaccharides comprised of conformationally restricted furan­ose residues. The furan­ose ring adopts an envelope conformation with the ring O atom displaced above the plane (an ^OE conformation). The pseudorotational phase angle (P) is 88.6° and the puckering amplitude (τ_m) is 31.5°. The C₂—C₁—S—C(Ph) torsion angle is ?163.2 (2)°, which places the aglycone in the exo‐anomeric effect preferred position. The C1—S—C14 bond angle is 99.02 (13)° and the plane of the cresyl moiety is oriented nearly parallel to the four in‐plane atoms of the furan­ose ring envelope. The orientation about the C4—C5 bond is gauche–gauche [Bock & Duus (1994). J. Carbohydr. Chem. 13 , 513–543].     

Methyl (SR)‐10‐chloro‐1,2,3,4,5,6‐hexahydro‐6‐hydroxy‐8‐methoxy‐1‐methyl‐1,9‐phenanthroline‐6‐carboxylate

In the title compound, C₁₆H₁₉ClN₂O₄, the pyridine ring is nearly planar, the piperidine ring is non‐planar and the cyclo­hexane ring adopts a screw‐boat conformation. The carboxyl­ate group makes a dihedral angle of 80.9 (2)° with the least‐squares plane through the cyclo­hexane ring.     

One‐Pot Synthesis of 4‐(2,3‐Dihydro‐2‐hydroxy‐1,3‐dioxo‐1H‐inden‐2‐yl)‐Substituted 1‐Aryl‐1H‐pyrazole‐3‐carboxylates via a Tandem Three‐Component Reaction

The hitherto unreported, highly functionalized 1H‐pyrazole‐3‐carboxylates 3 have been synthesized in good yields via a one‐pot three‐component domino reaction of phenylhydrazines, dialkyl acetylenedicarboxylates, and ninhydrin under mild conditions for the first time. No co‐catalyst or activator is required for this multicomponent reaction, and the reaction is, from an experimental point of view, simple to perform (Scheme 1). The structures of compounds 3 were corroborated spectroscopically (IR, ¹H‐ and ¹³C‐NMR, and EI‐MS) and by elemental analyses. A plausible mechanism for this type of cyclization/addition reaction is proposed (Scheme 2).     

Neue molekulare Indium‐Zinn‐Sauerstoff‐ und Indium‐Zinn‐Natrium‐Sauerstoff‐Chlor‐Cluster

Abstract. The five‐membered heteroelement cluster THF · Cl₂In(O^tBu)₃Sn reacts with the sodium stannate [Na(O^tBu)₃Sn]₂ to produce either the new oxo‐centered alkoxo cluster ClInO[Sn(O^tBu)₂]₃ ( 1 ) (in low yield) or the heteroleptic alkoxo cluster Sn(O^tBu)₃InCl₃Na[Sn(O^tBu)₂]₂ ( 2 ). X‐ray diffraction analyses reveal that in compound 1 the polycyclic entity is made of three tin atoms which together with a central oxygen atom form a trigonal, almost planar triangle, perpendicular to which a further indium atom is connected through the oxygen atom. The metal atoms thus are arranged in a Sn₃In pyramid, the edges of which are all saturated by bridging tert‐butoxy groups. The indium atom has a further chloride ligand. Compound 2 has two trigonal bipyramids as building blocks which are fused together at a six coordinate indium atom. One of the bipyramids is of the type SnO₃In with tert‐butyl groups on the oxygen atoms, while the other has the composition InCl₃Na with chlorine atoms connecting the two metals. The sodium atom in 2 has further contacts to two plus one alkoxide groups which are part of a[Sn(O^tBu)₂]₂ dimer disposing of a Sn₂O₂ central cycle. The hetero element cluster in 2 thus combines three closed entities and its skeleton SnO₃InCl₃NaO₂Sn₂O₂ consists of three different metallic and two different non‐metallic elements.     

1,1,1,1,4,4,4,4‐Octacarbonyl‐2,2,3,3,5,5,6,6‐octamethyl‐cyclo‐2,3,5,6‐tetraantimony‐1,4‐dichromium

The structure of the title compound, alternatively called bis(μ‐tetramethyldistibinediyl)bis(tetracarbonylchromium), [Cr₂Sb₄(CH₃)₈(CO)₈], consists of two Me₄Sb₂ bridging units between Cr(CO)₄ complex fragments. The centre of the molecule is located on a special position of 2/m symmetry. This is the first characterized Sb₄Cr₂ heterocycle.     

Ethyl 3,5‐dimethyl‐4‐phenyl‐1H‐pyrrole‐2‐carboxylate

In the title compound, C₁₅H₁₇NO₂, the ethoxy­carbonyl group is anti with respect to the pyrrole N atom. The angle between the planes of the phenyl and pyrrole rings is 48.26 (9)°. The mol­ecules are joined into dimeric units by a strong hydrogen bonds between pyrrole N—H groups and carbonyl O atoms. The geometry of the isolated mol­ecule was studied by ab initio quantum mechanical calculations, employing both molecular orbital Hartree–Fock (MO–HF) and density functional theory (DFT) methods. The minimum energy was achieved for a conformation where the angle between the planes of the phenyl and pyrrole rings is larger, and that between the ethoxy­carbonyl and pyrrole planes is smaller than in the solid‐state mol­ecule.     

5‐Phen­yl‐1,3,4‐thia­diazol‐2‐yl 2,3,4,6‐tetra­‐O‐acet­yl‐1‐thio‐β‐d‐glucopyran­oside

The structure of the title compound, C₂₂H₂₄N₂O₉S₂, is described. This compound consists of a sugar ring and a heterocyclic base linked unusually by an S atom. The sugar is in a ⁴C₁ chair conformation and forms dihedral angles of 49.54 (4) and 33.42 (5)° with the thia­diazole and phen­yl rings, respectively. The S atom occupies an equatorial position of the sugar ring and lies 1.807 (2) Å out of the corresponding mean plane.     

The achiral tetrapeptide Z‐Aib‐Aib‐Aib‐Gly‐OtBu

The title achiral peptide N‐benzyloxycarbonyl‐α‐aminoisobutyryl‐α‐aminoisobutyryl‐α‐aminoisobutyrylglycine tert‐butyl ester or Z‐Aib‐Aib‐Aib‐Gly‐OtBu (Aib is α‐aminoisobutyric acid, Z is benzyloxycarbonyl, Gly is glycine and OtBu indicates the tert‐butyl ester), C₂₆H₄₀N₄O₇, is partly hydrated (0.075H₂O) and has two different conformations which together constitute the asymmetric unit. Both molecules form incipient 3₁₀‐helices. They differ in the relative orientation of the N‐terminal protection group and at the C‐terminus. There are two 4→1 intramolecular hydrogen bonds.     

N‐Methyl­pyridinium 3‐cyano‐4‐(di­cyano­methyl­ene)‐5‐oxo‐4,5‐di­hydro‐1H‐pyrrol‐2‐olate

The crystal structure of the title compound, C₆H₈N⁺·C₈HN₄O₂⁻, is characterized by three independent ion pairs (A, B and C) in the asymmetric unit. Each ion pair consists of an anion and a cation, and the three ion pairs have similar geometric parameters. All the anions are arranged as dianion dimers via two N—H⋯O hydrogen bonds and the dimers form one‐dimensional columns parallel to the b axis as a result of π–π interactions. The cations are also stacked, in two different ways: one type of stacking consists of alternating A and B cations, while the other type consists of C cations only. Each dianion dimer stack is surrounded by eight stacks of cations and is not connected directly to other dianion stacks.     

4‐Hydroxy‐7‐methoxy‐2‐methyl‐5H‐1‐benzopyrano[4,3‐b]pyridin‐5‐one

The title compound, C₁₄H₁₁NO₄, consists of a methoxy‐substituted coumarin skeleton fused to a 2‐methyl‐4‐pyridone ring. The ring system of the mol­ecule is approximately planar and the methoxy group is roughly coplanar with the ring plane. The 4‐pyridone ring exists in a 4‐hydroxy tautomeric form and is stabilized by an intramolecular hydrogen bond between the O—H and C=O groups. Comparison of the results with those found for other structures containing the 4‐pyridone substructure reveals a substantial effect of the nature of the substituents bonded to the pyridine ring on the keto–enol tautomerism.     

N‐(2‐Acetamido‐3,4,6‐tri‐O‐acetyl‐2‐deoxy‐α‐d‐galactopyranosyloxy)­succinimide

The crystal structure of the title compound, C₁₈H₂₄N₂O₁₁, a GalNAc mimic containing an α‐gly­cosyl­oxy­succin­imide linkage, has been determined. The pyran­ose ring geometry is an almost perfect ⁴C₁ chair. The torsion angle of the exocyclic hydroxy­methyl group is shown to be gauche–trans with respect to O1 and C4, respectively.     

1,4,4‐Tri­methyl‐9‐phenyl‐8‐oxa‐9‐aza­bi­cyclo­[3.2.2]­non‐6‐en‐2‐one

The structure of the adduct of eucarvone with nitro­so­benzene, C₁₆H₁₉NO₂, is reported. The [3.2.2] bicyclic system corresponds to two seven‐membered rings in boat and distorted chair conformations and a six‐membered ring that adopts a distorted boat conformation. No conjugation is observed between the phenyl group and the N—O system. The packing is directed mainly by a C?O hydrogen bond, C—H?O‐(1 ? x, ?y, z) and by intermolecular C—H?π interactions.     

5‐Amino‐4‐(4‐diethyl­amino­phenyl)‐2‐(4‐hydroxy­phenyl)‐7‐(pyrrolidin‐1‐yl)‐1,6‐naphthyridine‐8‐carbo­nitrile

In the title compound, C₂₉H₃₀N₆O, the naphthyridine moiety is planar with a dihedral angle between the fused rings of 1.9 (1)°. The phenol ring is nearly coplanar, while the diethyl­amino­phenyl substituent is orthogonal to the central naphthyridine ring and the pyrrolidine ring makes an angle of 11.2 (1)° with it. The O atom of the hydroxy substituent is coplanar with the phenyl ring to which it is attached. The molecular structure is stabilized by a C—H?N‐type intramolecular hydrogen bond and the packing is stabilized by intermolecular C—H?π, O—H?N and N—H?O hydrogen bonds.     

From the Lithium‐2‐anilide‐2‐fluoro‐1,3‐diaza‐2‐sila‐cyclopentene‐GaCl3 Adduct to 1,4,6‐Triaza‐5‐gallium‐7‐sila‐cyclo‐3‐heptene ‐ Experimental and Quantum‐chemical Results

The lithium salt (HC–NCMe₃)₂SiFNLiR ( 1 ) R = C₆H₃(2,6‐CHMe₂)₂ reacts with trichlorogallium under displacement of the lithium ion by GaCl₃ to give the adduct [(HC–NCMe₃)₂SiFN]^– [(GaCl₃)R·Li(thf)₄]⁺ ( 1 ). Compound 1 thermally loses LiCl and forms the bicyclic ring intermediates V and VI . Compound  VI adds the aniline H₂NC₆H₃(2,6‐CHMe₂)₂ and the unsaturated, seven‐membered ring compound –NCMe₃–CH₂–CH=NCMe₃GaCl₂–NR–SiFNHR– ( 2 ) is obtained. The addition is accompanied by an enamine‐imine‐tautomerism and proves the Lewis acid character of the silicon atom in an unknown 3‐center‐2‐electron interaction of one nitrogen atom with the silicon and gallium atoms. Quantum chemical calculations of the thermal isomerisation process and crystal structures of 1 and 2 are reported.     

7‐Hydr­oxy‐6‐methoxy‐3‐[(2‐oxo‐2H‐1‐benzopyran‐7‐yl)oxy]‐2H‐1‐benzopyran‐2‐one

The title compound, daphnoretin, C₁₉H₁₂O₇, was isolated from the leaves of Stellera chamaejasme L. Two independent mol­ecules are present in the asymmetric unit, with similar conformations. Each of the independent mol­ecules is composed of two chromene systems connected by an ether bridge. The dihedral angles between the mean planes of the two chromene systems are 86.9 (2) and 81.9 (3)°. Mol­ecules form chains via hydrogen bonds and adjacent chains are parallel to each other.