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1.  4-Phenyl-1,2,4-tri­aza­spiro­[4.6]undec-1-ene-3-thione 
In the title compound, C14H17N3S, the plane of the phenyl ring makes a dihedral angle of 74.90 (4)° with that of the tri­aza­thione ring (r.m.s. deviation = 0.001 Å), while the seven-membered ring adopts a twist-chair conformation. No specific intermolecular interactions are discerned in the crystal packing.
doi:10.1107/S1600536814009817
PMCID: PMC4051002  PMID: 24940227
2.  Crystal structure of (1S,3R,8R,9R)-2,2-di­chloro-3,7,7-tri­methyl-10-methylenetri­cyclo­[6.4.0.01,3]dodecan-9-ol 
The title compound was synthesized by treating (1S,3R,8S,9R,10S)-2,2-di­chloro-3,7,7,10-tetra­methyl-9,10-ep­oxy­tri­cyclo­[6.4.0.01,3]dodecane with a concentrated solution of hydro­bromic acid. It is built up from three fused rings: a cyclo­heptane ring, a cyclo­hexyl ring bearing alkene and hy­droxy substituents, and a cyclo­propane ring bearing two chlorine atoms.
The title compound, C16H24Cl2O, was synthesized by treating (1S,3R,8S,9R,10S)-2,2-di­chloro-3,7,7,10-tetra­methyl-9,10-ep­oxy­tri­cyclo­[6.4.0.01,3]dodecane with a concentrated solution of hydro­bromic acid. It is built up from three fused rings: a cyclo­heptane ring, a cyclo­hexyl ring bearing alkene and hy­droxy substituents, and a cyclo­propane ring bearing two chlorine atoms. The asymmetric unit contains two mol­ecules linked by an O—H⋯O hydrogen bond. In the crystal, further O—H⋯O hydrogen bonds build up an R 4 4(8) cyclic tetra­mer. One of the mol­ecules presents disorder that affects the seven-membered ring. In both mol­ecules, the six-membered rings display a chair conformation, whereas the seven-membered rings display conformations inter­mediate between boat and twist-boat for the non-disordered mol­ecule and either a chair or boat and twist-boat for the disordered mol­ecule owing to the disorder. The absolute configuration for both mol­ecules is 1S,3R,8R,9R and was deduced from the chemical pathway and further confirmed by the X-ray structural analysis.
doi:10.1107/S2056989016011166
PMCID: PMC4971863  PMID: 27536404
crystal structure; absolute configuration; sesquiterpenes; asymmetric synthesis; natural products; crystal structure
3.  4-Phenyl-1,2,4-tri­aza­spiro­[4.5]dec-1-ene-3-thione 
In the title compound, C13H15N3S, the 4,5-di­hydro-3H-1,2,4-triazole ring is nearly planar [maximum deviation = 0.020 (1) Å], while the cyclo­hexane ring adopts a chair conformation. The dihedral angle between the 4,5-di­hydro-3H-1,2,4-triazole ring and the phenyl ring is 74.68 (7)°. No specific inter­molecular inter­actions are discerned in the crystal packing.
doi:10.1107/S1600536813019120
PMCID: PMC3793756  PMID: 24109343
4.  4-Phenyl-1,2,4-tri­aza­spiro­[4.4]non-1-ene-3-thione 
In the title compound, C12H13N3S, the 4,5-di­hydro-3H-1,2,4-triazole system is nearly planar [maximum deviation = 0.014 (2) Å], while the cyclo­pentane ring adopts a half-chair conformation. The dihedral angle between the mean plane of the 4,5-di­hydro-3H-1,2,4-triazole-3-thione ring and the phenyl ring is 85.49 (14)°, with the S atom 0.046 (1) Å out of the former plane. The crystal structure is stabilized only by van der Waals inter­actions. The investigated crystal was found to be a non-merohedral two-component twin by a 180° rotation about c*, with a refined value of the minor twin fraction of 0.12203 (18).
doi:10.1107/S1600536814005418
PMCID: PMC3998538  PMID: 24826140
5.  Crystal structure of 5′′-benzyl­idene-1′-methyl-4′-phenyl­tri­spiro­[ace­naphthyl­ene-1,2′-pyrrolidine-3′,1′′-cyclo­hexane-3′′,2′′′-[1,3]dioxane]-2,6′′-dione 
In the title tris­piro compound, both the methyl-substituted pyrrolidine and dioxalane rings adopt a twist conformation. The cyclo­penta­none ring of the acenapthylen-1-one system adopts flattened envelope conformation, and the cyclo­hexa­none attached to the dioxalane ring adopts boat conformation. In the crystal, centrosymmetrically related mol­ecules are linked into dimers forming rings of (10) graph-set motif, which are further connected into chains parallel to the b axis by C—H⋯O contacts forming rings of (8) graph-set motif.
In the title compound, C36H31NO4, two spiro links connect the methyl-substituted pyrrolidine ring to the ace­naphthyl­ene and cyclo­hexa­none rings. The cyclo­hexa­none ring is further connected to the dioxalane ring by a third spiro junction. The five-membered ring of the ace­naphthylen-1-one ring system adopts a flattened envelope conformation with the ketonic C atom as flap, whereas the dioxalane and pyrrolidine rings each have a twist conformation. The cyclo­hexa­none ring assumes a boat conformation. Three intra­molecular C—H⋯O hydrogen bonds involving both ketonic O atoms as acceptors are present. In the crystal, C—H⋯O hydrogen bonds connect centrosymmetrically related mol­ecule into chains parallel to the b axis, forming rings of R 2 2(10)and R 2 2(8) graph-set motifs.
doi:10.1107/S2056989016002875
PMCID: PMC4778841  PMID: 27006814
crystal structure; tris­piropyrrolidines; ace­naphthyl­ene; spiro­cyclo­hexa­nones; dioxalane
6.  5,6-Dimeth­oxy-4′,5′-diphenyl­indane-2-spiro-3′-pyrrolidine-2′-spiro-3′′-indoline-1,2′′-dione 
In the title compound, C33H28N2O4, the central pyrrolidine ring adopts a half-chair conformation. Both the indolinone and indanone groups are twisted, with their five-membered rings adopting a half-chair and an envelope conformation, respectively. The two benzene rings and the mean plane of the indolinone and indanone groups make dihedral angles of 71.98 (10), 84.32 (10), 86.26 (9) and 78.50 (9)°, respectively, with the central pyrrolidine ring. Intra­molecular C—H⋯O hydrogen bonds stabilize the mol­ecular conformation. In the crystal, pairs of inter­molecular N—H⋯O hydrogen bonds link the mol­ecules into centrosymmetric dimers. The dimers are inter­connected into ribbons propagating along [110] via weak inter­molecular C—H⋯O hydrogen bonds. Weak inter­molecular C—H⋯π and π–π [centroid–centroid distance = 3.6509 (11) Å] inter­actions are also observed.
doi:10.1107/S1600536810035865
PMCID: PMC2983396  PMID: 21587525
7.  (1′S,6′S,8′S,9′R)-9′-Bromo-12′-oxa­spiro­[1,3-dioxolane-2,4′-tricyclo­[6.3.1.01,6]dodeca­ne] 
In an endeavor directed towards the construction of the oxabicyclic[3.2.1]octane segment present in the bioactive natural products of cortistatins and icetexanes genre, the title compound, C13H19BrO3, was synthesized from (4aR,9aS)-1,3,4,4a,5,6,9,9a-octa­hydro­spiro­[benzo[7]annulene-2,2′-[1,3]dioxolane]-4a-ol via a transannular bromo-etherification protocol. The six-membered ring adopts a twist-boat conformation, while the fused cycloheptane ring adopts a chair conformation. The crystal packing is effected through two distinct inter­molecular C—H⋯O hydrogen-bond patterns and mol­ecules are arranged to define an inter­esting motif along the b axis.
doi:10.1107/S1600536812029777
PMCID: PMC3414332  PMID: 22904865
8.  2-(4-Methyl­pyridin-2-yl)-4′,4′,6′,6′-tetra­kis­(pyrrolidin-1-yl)-1H,2H-spiro­[naphtho­[1,2-e][1,3,2]oxaza­phosphinine-3,2′-[1,3,5,2,4,6]tri­aza­triphosphinine] 
In the title spiro-phosphazene derivative, C33H46N9OP3, the phosphazene and six-membered N/O rings are in flattened chair and twisted-boat conformations, respectively. The naphthalene ring system and the pyridine ring are oriented at a dihedral angle of 41.82 (4)°. In the crystal, weak C—H⋯O hydrogen bonds link the mol­ecules related by translation along the a axis into chains. C—H⋯π inter­actions aggregate these chains into layers parallel to the ab plane.
doi:10.1107/S1600536813014220
PMCID: PMC3685126  PMID: 23795145
9.  Crystal structures of two chiral piperidine derivatives: 1-[(1R)-2-hy­droxy-1-phenyl­eth­yl]piperidin-4-one and 8-[(1S)-1-phenyl­eth­yl]-1,4-dioxa-8-aza­spiro­[4.5]decane-7-thione 
The conformation of the piperidine ring is modified by the hybridization state of the C atom in the α-position to the piperidinic N atom.
The crystal structures of the two title piperidine derivatives show different conformations for the six-membered heterocycle. The N-substituted 4-piperidinone 1-[(1R)-2-hy­droxy-1-phenyl­eth­yl]piperidin-4-one, C13H17NO2, (I), has a chair conformation, while the piperidine substituted in position 2 with a thio­carbonyl group, 8-[(1S)-1-phenyl­eth­yl]-1,4-dioxa-8-aza­spiro­[4.5]decane-7-thione, C15H19NO2S, (II), features a half-chair conformation. Comparison of the two structures, and data retrieved from the literature, suggests that the conformational flexibility is mainly related to the hybridization state of the C atom α to the piperidinic N atom: a Csp 3 atom favours the chair conformer, while a Csp 2 atom distorts the ring towards a half-chair conformer. In the crystal structure of (I), weak C—H⋯O hydrogen bonds link the mol­ecules into supra­molecular chains propagating along the b-axis direction. In the crystal of (II), the mol­ecules are linked by weak C—H⋯S contacts into supra­molecular chains propagating along the b-axis direction.
doi:10.1107/S2056989015017119
PMCID: PMC4647425  PMID: 26594408
crystal structure; piperidine; piperidone; thione; ring conformation
10.  1-Benzyl-4′,5′-diphenyl­piperidine-3-spiro-3′-pyrrolidine-2′-spiro-3′′-indoline-4,2′′-dione 
The asymmetric unit of the title compound, C34H31N3O2, consists of two independent mol­ecules which differ slightly in the orientations of the phenyl rings with respect to the pyrrolidine ring. In both mol­ecules, the piperidin-4-one ring adopts a chair conformation, whereas the pyrrolidine ring adopts an envelope conformation in one of the mol­ecules and a twisted conformation in the other. An intra­molecular C—H⋯O hydrogen bond is observed. The crystal packing is stabilized by inter­molecular N—H⋯O hydrogen bonds and C—H⋯π inter­actions.
doi:10.1107/S160053680804141X
PMCID: PMC2968062  PMID: 21581605
11.  (1′S,12′R,13′S,17′S)-15′,15′-Dimethyl-1,2-dihydro-11′,14′,16′,18′-tetra­oxa-7′-aza­spiro­[indole-3,8′-penta­cyclo­[10.6.0.02,9.03,7.013,17]octa­deca­ne]-2,10′-dione 
In the title compound, C22H24N2O6, the indole ring has a twist conformation and the tetra­hydro-2H-pyran-2-one ring a half-chair conformation. One of the pyrrolidine rings adopts an envelope conformation on the N atom, while the other has a twist conformation; the ‘butterfly’ angle between their mean planes is 62.98 (11)°. The dioxolane ring adopts a twist conformation and the tetra­hydro­furan ring has an envelope conformation on the C atom in the fused tetra­hydro-2H-pyran-2-one ring adjacent to the O atom of the tetra­hydro­furan ring. The ‘butterfly’ angle between the mean planes of these two five-membered rings is 69.14 (10)°. In the crystal, mol­ecules are linked by N—H⋯O hydrogen bonds, forming chains along the a axis.
doi:10.1107/S1600536813005436
PMCID: PMC3629507  PMID: 23634025
12.  (4′-Acet­yloxy-1,3,1′-trioxo-1,3,4,4a,4b,5,6,7,9,9a-deca­hydro­spiro­[indene-2,9′-pyrano[4,3-a]pyrrolizin]-3′-yl)methyl acetate 
In the title compound, C23H23NO8, the dihedral angle between the five- and six-membered rings of the indene-dione moiety is 3.09 (13)°. The mean plane of the five-membered ring (which has a flat envelope conformation with the spiro C atom as the flap) is inclined to the mean plane of the central five-membered ring of the pyrrolizine unit by 76.48 (12)°. This central ring has a twist conformation on the N—C(spiro) bond. The outer ring of the pyrrolizine unit has an envelope conformation with the N atom as the flap. The mean planes of these two fused rings are inclined to one another by 65.28 (15)°. The pyran ring has a screw-boat conformation and its mean plane makes a dihedral angle of 29.50 (11)° with the mean plane of the central five-membered ring of the pyrrolizine unit. In the crystal, mol­ecules are linked via C—H⋯O hydrogen bonds, forming two-dimensional networks lying parallel to the ab plane.
doi:10.1107/S1600536813029826
PMCID: PMC3885038  PMID: 24454214
13.  Crystal structure of 5′′-(4-chloro­benzyl­idene)-4′-(4-chloro­phen­yl)-1′-methyltri­spiro[acenapthylene-1,2′-pyrrolidine-3′,1′′-cyclo­hexane-3′′,2′′′-[1,3]dioxane]-2(1H),6′′-dione 
In the title compound, C36H29Cl2NO4, two spiro links connect the methyl-substituted pyrrolidine ring to the ace­naphthyl­ene and cyclo­hexa­none rings. The cyclo­hexa­none ring is further connected to the dioxalane ring by a third spiro junction. The five-membered ring of the ace­naphthylen-1-one ring system adopts a flattened envelope conformation, with the ketonic C atom as the flap, whereas the dioxalane and pyrrolidine rings each have a twist conformation. The cyclo­hexenone ring assumes a boat conformation. An intra­molecular C—H⋯O hydrogen-bond inter­action is present. In the crystal, mol­ecules are linked by non-classical C—H⋯O hydrogen bonds, forming chains extending parallel to the a axis.
doi:10.1107/S2056989015018034
PMCID: PMC4645075  PMID: 26594541
crystal structure; spiro pyrrolidines; ace­naphthyl­ene; dioxalane; hydrogen bonding
14.  3-Methyl-1,2,3,4,5,6,1′,2′,3′,4′-deca­hydro­spiro­[benz[f]isoquinoline-1,2′-naphthalen]-1′-one 
The title compound, C23H23NO, is the product of a tandem transformation of the double Mannich base bis­(1-oxo-1,2,3,4-tertrahydro-2-naphtho­ylmeth­yl)amine hydro­chloride in HBr solution upon heating. The tetra­hydro­pyridine ring has a non-symmetrical half-chair conformation, whereas the cyclo­hexa­diene and cyclo­hexene rings adopt non-symmetrical half-boat conformations. The dihedral angle between the planes of the terminal benzene rings is 62.85 (6)°. The N atom has a trigonal–pyramidal geometry [sum of the bond angles = 332.4 (3)°]. In the crystal, mol­ecules form [001] chains via weak non-classical C—H⋯N hydrogen bonds. The chains are stacked along the b axis.
doi:10.1107/S1600536812043309
PMCID: PMC3515312  PMID: 23284532
15.  Crystal structure of (±)-(7RS,8SR)-7-methyl-1,4-dioxa­spiro­[4.5]decane-7,8-diol 
In the title compound, the dioxolane and cyclo­hexane rings adopt twist and chair conformations, respectively. In the crystal, intra- and inter­molecular O—H⋯O hydrogen bonds are observed.
In the title compound, C9H16O4, the five-membered dioxolane ring adopts a twist conformation; two adjacent C atoms deviate alternately from the mean plane of other atoms by −0.297 (4) and 0.288 (4) Å. The spiro-fused cyclo­hexane ring shows a chair form. The hy­droxy group substituted in an axial position makes an intra­molecular O—H⋯O hydrogen bond with one of the O atoms in the cyclic ether, forming an S(6) ring motif. In the crystal, the O—H⋯O hydrogen bond involving the equatorial hy­droxy group connects the mol­ecules into a zigzag chain with a C(5) motif running along the c axis.
doi:10.1107/S2056989015016783
PMCID: PMC4647432  PMID: 26594401
crystal structure; hydrogen bonds; paclitaxel; cyclo­hexa­ne; hy­droxy groups
16.  1′-Phenyl-6′-thia­cyclo­heptane-1-spiro-2′-perhydro­pyrrolizine-3′-spiro-3′′-indoline-2,2′′-dione 
The thia­zolidine ring and the pyrrolidine ring in the title compound, C25H26N2O2S, both adopt an envelope conformation. The seven-membered ring has a twist-chair conformation. The crystal packing is stabilized by inter­molecular N—H⋯O hydrogen bonds.
doi:10.1107/S1600536807068705
PMCID: PMC2960420  PMID: 21201511
17.  Methyl (3S,10b’S)-5-chloro-9′-fluoro-1-methyl-2-oxo-5′-phenyl-10b’H-spiro­[indoline-3,1′-pyrazolo­[3,2-a]iso­quinoline]-2′-carboxyl­ate 
In the title compound, C27H19ClFN3O3, the pyrazole ring has a twist conformation and the six-membered ring to which it is fused has a screw-boat conformation. The mean plane of the pyrazole ring is inclined to the 2-methyl­indoline ring by 85.03 (9) and by 28.17 (8)° to the mean plane of the iso­quinoline ring system. In the crystal, mol­ecules are linked by pairs of C—H⋯F hydrogen bonds, forming inversion dimers. These dimers are linked via C—H⋯O hydrogen bonds, forming a two-dimensional network lying parallel to (10-1).
doi:10.1107/S1600536813011549
PMCID: PMC3684913  PMID: 23795015
18.  1-Ethyl-4′-(1H-indol-3-ylcarbon­yl)-1′-methyl-2,2′′-dioxodi­spiro­[indoline-3,2′-pyrrolidine-3′,3′′-indoline]-4′-carbo­nitrile dimethyl sulfoxide monosolvate 
In the title compound, C31H25N5O3·C2H6OS, the three indole/indoline units are all essentially planar with maximum deviations of 0.0172 (3), 0.053 (2) and 0.07 (2) Å. The pyrrolidine ring adopts an envelope conformation with the C atoms bearing the 1-ethyl-2-oxo­indole substituent (in which the five-membered ring adopts a twisted conformation) as the flap. The dimethyl sulfoxide solvent mol­ecule is disordered over two positions, with an occupancy factor ratio of 0.871 (4):0.129 (4). The solvent components are linked to the heterocyclic mol­ecule via C—H⋯O and C—H⋯S hydrogen bonds. In the crystal, the solvent components are linked to the heterocyclic molecule via C—H⋯O and C—H⋯S inter­actions, forming R 2 2(10) ring motifs. The mol­ecules are further connected into a chain along the a-axis direction via N—H⋯O hydrogen bonds.
doi:10.1107/S1600536813020485
PMCID: PMC3793813  PMID: 24109400
19.  1′-Benzyl-4,4′′-bis­(4-chloro­phen­yl)-3-(2,6-dichloro­phen­yl)-1′′-methyl-4,5-dihydro­isoxazole-5-spiro-3′-piperidine-5′-spiro-3′′-pyrrolidine-2′′-spiro-3′′′-indoline-2′′′,4′-dione 
The asymmetric unit of the title compound, C43H34Cl4N4O3, contains two crystallographically independent mol­ecules. In both mol­ecules, the pyrrolidine ring adopts a twist conformation, the oxindole units are slightly distorted from planarity and the isoxazoline ring adopts an envelope conformation. The crystal structure is stabilized by N—H⋯O hydrogen-bonding inter­actions giving one-dimensional chain structures.
doi:10.1107/S1600536809053276
PMCID: PMC2980235  PMID: 21580030
20.  Crystal structure of rac-3,9-bis­(2,6-di­fluoro­phen­yl)-2,4,8,10-tetra­oxa­spiro[5.5]undeca­ne 
The title compound, C19H16F4O4, was prepared by the condensation reaction of 2,6-di­fluoro­benzaldehyde and penta­erythritol. The whole mol­ecule is generated by twofold rotational symmetry. The two six-membered O-heterocycles adopt chair conformations through a shared spiro-carbon atom that is located on the crystallographic twofold rotation axis. In this conformation, the two aromatic rings are located at the equatorial positions of the O-heterocycles. The conformation of this doubly substituted tetra­oxa­spiro system is chiral. In the crystal, mol­ecules are linked by C—H⋯O hydrogen bonds, forming layers parallel to (100). These layers are linked by C—H⋯F hydrogen bonds into a three-dimensional structure.
doi:10.1107/S2056989015001206
PMCID: PMC4384547  PMID: 25878866
crystal structure; oxo-spiro­cyclic; helical hydrogen-bonded chains; axial chirality
21.  5-Amino-5′-bromo-6-(4-methyl­benzo­yl)-8-nitro-2,3-di­hydro-1H-spiro­[imidazo[1,2-a]pyridine-7,3′-indolin]-2′-one including an unknown solvate 
In the title compound, C22H18BrN5O4, the central six-membered ring, derived from 1,4-di­hydro­pyridine, adopts a distorted boat conformation with a puckering amplitude of 0.197 (3) Å, the imidazole ring adopts a twisted conformation with a puckering amplitude of 0.113 (3) Å, and the oxindole moiety is planar with an r.m.s. deviation of 0.0125 Å. Two intra­molecular N—H⋯O hydrogen bonds are formed, each closing an S(6) loop. In the crystal, strong N—H⋯O hydrogen bonds lead to the formation of zigzag chains along the c axis. These are consolidated in the three-dimensional crystal packing by weak N—H⋯O hydrogen bonding, as well as by C—H⋯O, C—H⋯Br and C—H⋯π inter­actions. A small region of electron density well removed from the main mol­ecule was removed with the SQUEEZE procedure in PLATON [Spek (2009 ▶). Acta Cryst. D65, 148–155] following unsuccessful attempts to model it as a plausible solvent mol­ecule. The unit-cell characteristics do not take into account this feature of the structure.
doi:10.1107/S1600536814014391
PMCID: PMC4120621  PMID: 25161594
crystal structure
22.  Crystal structure of ethyl 5′′-fluoro-2′′,3-dioxo-6′,7′,8′,8a’-tetra­hydro-2′H,3H,5′H-di­spiro­[benzo[b]thio­phene-2,1′-indol­izine-3′,3′′-indoline]-2′-carboxyl­ate 
In the title compound, C25H23FN2O4S, the fused piperidine ring of the octa­hydro­indolizine ring system adopts a chair conformation and the five-membered ring has a twisted conformation on the N—C(spiro) bond. The mean planes of the benzo­thio­phene and indoline ring systems are inclined to the mean plane of the pyrrolidine ring by 83.1 (1) and 84.9 (1)°, respectively, and to each other by 29.37 (17)°. In the crystal, mol­ecules are linked via pairs of N—H⋯O hydrogen bonds, forming inversion dimers with an R 2 2(8) ring motif. The dimers are linked via C—H⋯O hydrogen bonds, forming slabs lying parallel to (100). The packing between the slabs features a short [2.734 (2) Å] F⋯F contact.
doi:10.1107/S2056989015002121
PMCID: PMC4350745  PMID: 25844224
crystal structure; di­spiro; benzo­thio­phene; indolizine; indoline; F⋯F inter­actions; hydrogen bonds
23.  Crystal structure of (1S,2S,2′R,3a′S,5R)-2′-[(5-bromo-1H-indol-3-yl)meth­yl]-2-isopropyl-5,5′-dimethyl­dihydro-2′H-spiro­[cyclo­hexane-1,6′-imidazo[1,5-b]isoxazol]-4′(5′H)-one 
The absolute structure for the title compound, which has five chiral centres has been determined in this analysis. The supra­molecular architecture comprises parallel zigzag chains formed through N—H⋯N and C—H⋯O hydrogen bonds, as well as intra­molecular C—H⋯O, C—H⋯N and C—H⋯π inter­actions.
In the title compound, C24H32BrN3O2, the six-membered cyclo­hexane ring adopts a chair conformation and the isoxasolidine ring adopts a twisted conformation. The mol­ecule has five chiral centres and the absolute configuration has been determined in this analysis. The mol­ecular structure is stabilized by weak intra­molecular C—H⋯O and C—H⋯N contacts. In the crystal, mol­ecules are linked by N—H⋯N and C—H⋯O hydrogen bonds, forming undulating sheets parallel to the bc plane.
doi:10.1107/S2056989016010872
PMCID: PMC4971846  PMID: 27536387
crystal structure; isoxazolidines; 1,3-dipolar cyclo­addition; chiral nitrone; hydrogen bonding
24.  8-Methyl-4-morpholinoethyl-1-thia-4-aza­spiro­[4.5]decan-3-one 
In the title compound, C15H26N2O2S, the cyclo­hexane and morpholine rings adopt chair conformations, while the thia­zole ring has a twist conformation. An intra­molecular C—H⋯S hydrogen-bond inter­action forms a five-membered ring. The crystal packing involves C—H⋯O=C inter­molecular inter­actions where carbonyl O atoms act as double acceptors to two symmetrically related H atoms.
doi:10.1107/S1600536808022459
PMCID: PMC2962192  PMID: 21203273
25.  Ethyl 2-(1,2,3,4-tetrahydro­spiro­[carba­zole-3,2′-[1,3]dioxolan]-9-yl)acetate 
In the title compound, C18H21NO4, the hydrogenated six-membered ring of the carbazole unit adopts a half-chair conformation. The dioxolane ring and ethyl­acetate substituent point to opposite sides of the carbazole plane. The ethyl­acetate substituent adopts an essentially fully extended conformation, and its mean plane forms a dihedral angle of 83.8 (1)° with respect to the carbazole mean plane. The mol­ecules are arranged into stacks in which the carbazole planes form a dihedral angle of 4.4 (1)° and have an approximate inter­planar separation of 3.6 Å.
doi:10.1107/S160053680900748X
PMCID: PMC2969037  PMID: 21582427

Results 1-25 (263879)