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1.
Ann Oncol ; 27(10): 1947-53, 2016 10.
Artículo en Inglés | MEDLINE | ID: mdl-27502712

RESUMEN

BACKGROUND: Genomic profiling of tumor tissue may aid in identifying predictive or prognostic gene signatures (GS) in some cancers. Retrospective gene expression profiling of melanoma and non-small-cell lung cancer led to the characterization of a GS associated with clinical benefit, including improved overall survival (OS), following immunization with the MAGE-A3 immunotherapeutic. The goal of the present study was to prospectively evaluate the predictive value of the previously characterized GS. PATIENTS AND METHODS: An open-label prospective phase II trial ('PREDICT') in patients with MAGE-A3-positive unresectable stage IIIB-C/IV-M1a melanoma. RESULTS: Of 123 subjects who received the MAGE-A3 immunotherapeutic, 71 (58.7%) displayed the predictive GS (GS+). The 1-year OS rate was 83.1%/83.3% in the GS+/GS- populations. The rate of progression-free survival at 12 months was 5.8%/4.1% in GS+/GS- patients. The median time-to-treatment failure was 2.7/2.4 months (GS+/GS-). There was one complete response (GS-) and two partial responses (GS+). The MAGE-A3 immunotherapeutic was similarly immunogenic in both populations and had a clinically acceptable safety profile. CONCLUSION: Treatment of patients with MAGE-A3-positive unresectable stage IIIB-C/IV-M1a melanoma with the MAGE-A3 immunotherapeutic demonstrated an overall 1-year OS rate of 83.5%. GS- and GS+ patients had similar 1-year OS rates, indicating that in this study, GS was not predictive of outcome. Unexpectedly, the objective response rate was lower in this study than in other studies carried out in the same setting with the MAGE-A3 immunotherapeutic. Investigation of a GS to predict clinical benefit to adjuvant MAGE-A3 immunotherapeutic treatment is ongoing in another melanoma study.This study is registered at www.clinicatrials.gov NCT00942162.


Asunto(s)
Antígenos de Neoplasias/genética , Melanoma/genética , Melanoma/terapia , Proteínas de Neoplasias/genética , Adulto , Anciano , Anciano de 80 o más Años , Antígenos de Neoplasias/inmunología , Antígenos de Neoplasias/uso terapéutico , Supervivencia sin Enfermedad , Femenino , Regulación Neoplásica de la Expresión Génica , Genómica , Humanos , Inmunoterapia/efectos adversos , Inmunoterapia/métodos , Masculino , Melanoma/inmunología , Melanoma/patología , Persona de Mediana Edad , Proteínas de Neoplasias/inmunología , Proteínas de Neoplasias/uso terapéutico , Estadificación de Neoplasias , Transcriptoma/genética
2.
J Exp Med ; 182(3): 689-98, 1995 Sep 01.
Artículo en Inglés | MEDLINE | ID: mdl-7544395

RESUMEN

Human melanoma MZ2-MEL expresses several distinct antigens that are recognized by autologous cytolytic T lymphocytes (CTL). Some of these antigens are encoded by genes MAGE-1, MAGE-3, and BAGE, which are expressed in a large fraction of tumors of various histological types but are silent in normal adult tissues with the exception of testis. We report here the identification of the gene coding for MZ2-F, another antigen recognized by autologous CTL on MZ2-MEL cells. This gene, which was named GAGE-1, is not related to any presently known gene. It belongs to a family of genes that are expressed in a variety of tumors but not in normal tissues, except for the testis. Antigenic peptide YRPRPRRY, which is encoded by GAGE-1, is recognized by anti-MZ2-F CTL on class I molecule HLA-Cw6. The two genes of the GAGE family that code for this peptide, namely GAGE-1 and GAGE-2, are expressed in a significant proportion of melanomas (24%), sarcomas (25%), non-small cell lung cancers (19%), head and neck tumors (19%), and bladder tumors (12%). About 50% of melanoma patients carry on their tumor at least one of the presently defined antigens encoded by the MAGE, BAGE, and GAGE genes.


Asunto(s)
Antígenos de Neoplasias/genética , Melanoma/inmunología , Familia de Multigenes , Proteínas de Neoplasias , Linfocitos T Citotóxicos/inmunología , Secuencia de Aminoácidos , Animales , Antígenos de Neoplasias/biosíntesis , Antígenos de Neoplasias/inmunología , Secuencia de Bases , Línea Celular Transformada , Chlorocebus aethiops , ADN Complementario/genética , ADN de Neoplasias/genética , Epítopos/química , Epítopos/inmunología , Feto/metabolismo , Regulación Neoplásica de la Expresión Génica , Antígenos HLA-C/inmunología , Células HeLa , Humanos , Melanoma/genética , Antígenos Específicos del Melanoma , Datos de Secuencia Molecular , Neoplasias/inmunología , Especificidad de Órganos , Fragmentos de Péptidos/química , Fragmentos de Péptidos/inmunología , ARN Mensajero/biosíntesis , ARN Neoplásico/biosíntesis , Alineación de Secuencia , Homología de Secuencia , Transfección , Células Tumorales Cultivadas
3.
J Med Chem ; 33(6): 1833-9, 1990 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-2342078

RESUMEN

In view of the selective anti-HIV activity of 2',3'-dideoxy-3'-fluoro-5-chlorouridine (11), a series of eight 2',3'-dideoxy-5-chloropyrimidines were synthesized and evaluated for their inhibitory activity against human immunodeficiency virus type 1 (HIV-1) replication in MT-4 cells. A marked improvement in selectivity was noted for the 5-chlorouracil derivatives of 2,3-dideoxyribofuranose, 3-azido-2,3-dideoxyribofuranose, and 3-fluoro-2,3-dideoxyribofuranose, mainly due to decreased toxicity of the compounds for the host cells. While chlorination of 2',3'-dideoxycytidine removed the anti-HIV activity, introduction of a chlorine at the C-5 position of 3'-fluoro-, 3'-azido- or 2',3'-didehydro-2',3'-dideoxycytidine led to reduced cytotoxicity with only slightly reduced anti-HIV activity. X-ray analysis showed compound 11 to have two molecules in the asymmetric unit with chi = -168.8 (3) degrees and -131.3 (3) degrees and P = 179 (1) degree and 163 (1) degree, respectively; thus revealing no close resemblance to 3'-azido-3'-deoxythymidine (AZT).


Asunto(s)
Antivirales/síntesis química , Didesoxinucleósidos/síntesis química , VIH/efectos de los fármacos , Antivirales/farmacología , Antivirales/toxicidad , Línea Celular , Didesoxinucleósidos/farmacología , Didesoxinucleósidos/toxicidad , Humanos , Conformación Molecular , Difracción de Rayos X
4.
J Med Chem ; 38(19): 3838-49, 1995 Sep 15.
Artículo en Inglés | MEDLINE | ID: mdl-7562915

RESUMEN

In continuation of a project aimed at the structure-based design of drugs against sleeping sickness, analogs of 2'-deoxy-2'-(3-methoxybenzamido)adenosine (1) were synthesized and tested to establish structure-activity relationships for inhibiting glycosomal glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Compound 1 was recently designed using the NAD:GAPDH complexes of the human enzyme and that of Trypanosoma brucei, the causative agent of sleeping sickness. In an effort to exploit an extra hydrophobic domain due to Val 207 of the parasite enzyme, several new 2'-amido-2'-deoxyadenosines were synthesized. Some of them displayed an interesting improvement in inhibitory activity compared to 1. Carbocyclic or acyclic analogs showed marked loss of activity, illustrating the importance of the typical (C-2'-endo) puckering of the ribose moiety. We also describe the synthesis of a pair of compounds that combine the beneficial effects of a 2- and 8-substituted adenine moiety on potency with the beneficial effect of a 2'-amido moiety on selectivity. Unfortunately, in both cases, IC50 values demonstrate the incompatibility of these combined modifications. Finally, introduction of a hydrophobic 5'-amido group on 5'-deoxyadenosine enhances the inhibition of the protozoan enzyme significantly, although the gain in selectivity is mediocre.


Asunto(s)
Desoxiadenosinas/síntesis química , Desoxiadenosinas/farmacología , Inhibidores Enzimáticos/síntesis química , Inhibidores Enzimáticos/farmacología , Gliceraldehído-3-Fosfato Deshidrogenasas/antagonistas & inhibidores , Trypanosoma brucei brucei/enzimología , Animales , Sitios de Unión , Cristalografía por Rayos X , Desoxiadenosinas/química , Inhibidores Enzimáticos/química , Humanos , Espectroscopía de Resonancia Magnética , Conformación Molecular , Unión Proteica , Relación Estructura-Actividad
5.
J Med Chem ; 40(23): 3765-72, 1997 Nov 07.
Artículo en Inglés | MEDLINE | ID: mdl-9371242

RESUMEN

The present study explores the C-3' site of the 3-deoxy-3-xylofuranosyl ring of nucleoside analogues with an adenine or N6-cyclopentyladenine (CPA) base moiety and evaluates the effect on adenosine receptor affinity. Two series of sugar-modified adenosines, i.e., 3'-amido-3'-deoxyadenosines and 3'-amidated 3'-deoxyxylofuranosyladenines, were synthesized and tested for their affinity at A1 and A2a receptors in rat brain cortex and rat striatum, respectively. The modest affinity found in the "xylo series" prompted us to synthesize the corresponding N6-cyclopentyl derivatives, which proved to be well accommodated by the A1 receptors with potencies in the lower nanomolar range. This represents a new perspective in the purinergic field. The absence of a GTP-induced shift, i.e., the ratio between the affinities measured in the presence and absence of 1 mM GTP indicates an antagonistic behavior of this new class of CPA analogues.


Asunto(s)
Adenosina/análogos & derivados , Antagonistas de Receptores Purinérgicos P1 , Adenosina/síntesis química , Adenosina/farmacología , Animales , Sitios de Unión , Cristalografía por Rayos X , Ensayo de Unión Radioligante , Ratas , Receptores Purinérgicos P1/metabolismo , Xantinas/farmacología
6.
Antiviral Res ; 14(6): 357-69, 1990 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-2088211

RESUMEN

1-(2-Azido-2,3-dideoxy-beta-D-erythro-pentofuranosyl)thymine (2'-N3ddThd) was synthesized from 1-(5-O-trityl-2,3-anhydro-beta-D-lyxofuranosyl)thymine by two different procedures. Method A prepared the title compound by opening of the oxirane ring with LiEt3BH followed by mesylation of the 2'-hydroxyl function, introduction of the 2'-azido substituent and deblocking of the 5'-function. In method B nucleophilic opening of 3'-deoxy-5'-O-(tert-butyldimethylsilyl)-5-methyl-2,2'-anhydrouridine+ ++ was carried out with sodium azide in hexamethylphosphoramide in the presence of benzoic acid. Single X-ray crystallographic studies indicated a solid state conformation (3T2), which was opposite to that of the A form of AZT (2T3) but closely resembled that of 1-(2-fluoro-2,3-dideoxy-beta-D-erythropentofuranosyl)thymine (2'-FddThd) (3T2) and of 3'-azido-2',3'-dideoxy-2,6-diaminopurine riboside (3'-N3ddDAP) (3T2). Whereas the latter displayed significant inhibitory activity against human immunodeficiency virus (HIV) replication, 2'-FddThd and 2'-N3ddThd were essentially inactive.


Asunto(s)
Antivirales/síntesis química , VIH/efectos de los fármacos , Zidovudina/análogos & derivados , Cristalografía , Didesoxinucleósidos/química , Didesoxinucleósidos/farmacología , Humanos , Técnicas In Vitro , Estructura Molecular , Relación Estructura-Actividad , Replicación Viral/efectos de los fármacos , Difracción de Rayos X , Zidovudina/síntesis química , Zidovudina/química
7.
Acta Crystallogr C ; 56(Pt 3): E98-9, 2000 Mar 15.
Artículo en Inglés | MEDLINE | ID: mdl-15263214

RESUMEN

The title compound, (C(6)H(5)CH(2))(3)PO, is an organic tertiary phosphine oxide. The molecule has threefold symmetry, with the P-O bond along the threefold axis. Main dimensions include P-O 1.488 (4), P-C 1.823 (3) A and O-P-C 114.7 (1) degrees. The crystals were accidentally obtained when preparing complexes of nickel(II) with dibenzylphosphine.

8.
Acta Chir Belg ; 89(1): 54-7, 1989.
Artículo en Inglés | MEDLINE | ID: mdl-2718685

RESUMEN

Solitary exulceratio simplex (ulcer of Dieulafoy--Dieulafoy vascular malformation) is a rare and frequently overlooked cause of massive gastric hemorrhage. The source of the bleeding, a large, submucosal artery penetrating the centre of a small mucosal defect, is usually located in the upper portion of the stomach. The pathogenesis of this entity is not known. We report on two patients who were successfully treated by surgery. Clinical, morphological and pathogenetic aspects are discussed.


Asunto(s)
Hematemesis/etiología , Melena/etiología , Úlcera Gástrica/complicaciones , Adulto , Femenino , Humanos , Masculino , Persona de Mediana Edad , Úlcera Gástrica/patología , Úlcera Gástrica/cirugía , Síndrome
9.
J Pharm Belg ; 54(2): 48-50, 1999.
Artículo en Inglés | MEDLINE | ID: mdl-10454882

RESUMEN

The purpose of this research is to characterize the possible vascular selectivity of a series of novel bicyclic compounds derived from 3,4-dihydropyridones. We describe the synthesis, structural study by X-ray analysis and quantum chemical calculations at semiempirical (AMI) and ab initio (HF/321G) levels and pharmacological activity of these 4-aryl-7,7-dimethyl-2,5-dioxo-1,2,3,4,5,6,7,8-octahydroquinolines. In addition, the more favoured conformation for compounds 4a-c in solution was determined from the calculated and experimental proton coupling constants. We report the first computational study on the structure of octahydroquinolines. The results of ab initio (HF/3-21G) and semiempirical molecular orbital calculations (AMI) are compared with the data obtained by X-ray crystallographic study for 4a.


Asunto(s)
Bloqueadores de los Canales de Calcio/síntesis química , Dihidropiridinas/síntesis química , Quinolinas/síntesis química , Animales , Bloqueadores de los Canales de Calcio/farmacología , Dihidropiridinas/farmacología , Técnicas In Vitro , Estructura Molecular , Contracción Muscular/efectos de los fármacos , Músculo Liso Vascular/efectos de los fármacos , Músculo Liso Vascular/fisiología , Quinolinas/farmacología , Conejos
11.
Acta Crystallogr C ; 45 ( Pt 12): 1930-3, 1989 Dec 15.
Artículo en Inglés | MEDLINE | ID: mdl-2576841

RESUMEN

alpha,alpha'-1,1'-Bis(3,4-dihydro-2H-benzopyran-2-yl)-2,2'-iminodieth anol hydrobromide. (I) C22H28NO4+.Br-, Mr = 450.37, orthorhombic, P2(1)2(1)2(1), a = 5.1278(1), b = 13.1699(6), c = 30.858(2) A, V = 2083.9(2)A3, Z = 4, Dm = 1.44, D chi = 1.436 Mg m-3, lambda(Cu K alpha) = 1.54178 A, mu(Cu K alpha) = 2.915 mm-1, F(000) = 936, room temperature, final R = 0.054 for 2086 observed reflections. (II) C22H28NO4+.Br-, Mr = 450.37, orthorhombic, P2(1)2(1)2(1), a = 5.1292(2), b = 13.1764(9), c = 30.847(3) A, V = 2084.8(3)A3 lambda(Cu K alpha) = 1.54178A, mu(Cu K alpha) = 2.915 mm-1, F(000) = 936, room temperature, final R = 0.054 for 2676 observed reflections. The two structures are mirror images and the central C--C--N--C--C chain adopts the anti-periplanar-synclinal conformation. The active beta 1-selective adrenergic receptor blocker [isomer (I)] has the S,R,R,S absolute configuration while the inactive isomer (II) has the R,S,S,R configuration. Endless chains are formed by (N-)H...Br hydrogen bonds in the a direction and by (O-)H...Br hydrogen bonds in the b direction.


Asunto(s)
Antagonistas Adrenérgicos beta , Benzopiranos , Estereoisomerismo , Difracción de Rayos X
12.
Acta Crystallogr C ; 45 ( Pt 5): 799-803, 1989 May 15.
Artículo en Inglés | MEDLINE | ID: mdl-2557866

RESUMEN

C16H22NO+2.Cl-, Mr = 295.808, monoclinic, P2(1), a = 11.967 (1), b = 12.529 (1), c = 9.9369 (9) A, beta = 93.00 (1) degrees, V = 1487.8 (2) A3, Z = 4, Dm = 1.32 (2), Dx = 1.321 Mg m-3, lambda(Cu K alpha) = 1.54178 A, mu(Cu K alpha) = 2.289 mm-1, F(000) = 632, T = 291 K, final R = 0.040 for 2448 observed reflections. The two molecules present in the asymmetric unit are linked by an extensive network of hydrogen bonds, including several of the less common (C-)H...O and (C-)-H...Cl types. This interpretation is substantiated by a Mulliken population analysis resulting from CNDO/2 calculations. The major effect of the presence of the epoxyethano bridge is a marked flattening about the N atom of the piperidinium ring. Whether this is sufficient to explain the inactivity of the compound at the opioid kappa receptor is not clear.


Asunto(s)
Benzomorfanos , Morfinanos , Receptores Opioides/metabolismo , Benzomorfanos/síntesis química , Cristalización , Cristalografía , Enlace de Hidrógeno , Estructura Molecular , Morfinanos/síntesis química , Receptores Opioides kappa , Relación Estructura-Actividad
13.
Acta Crystallogr C ; 55 ( Pt 3): 458-61, 1999 Mar 15.
Artículo en Inglés | MEDLINE | ID: mdl-10220874

RESUMEN

The single-crystal X-ray structures of (-)-dimethyl[(2S)-1-(5,6,7,8- tetrahydro-5-oxonaphthalene-2-acetyl)piperidin-2-ylmethyl ]ammonium chloride, C20H29N2O2+.Cl-(BRL-53001A), and (-)-ethylmethyl[(2S)-1-(5,6,7,8-tetrahydro-5-oxonaphthalene- 2- acetyl)piperidin-2-ylmethyl]-ammonium chloride dihydrate, C21H31N2O2+.Cl-.2H2O (BRL-53188A), have been determined. The two molecules have different conformations in the 1-tetralon-6-ylacetyl residue but the same conformation in the 1-acetyl-2-(dialkylaminomethyl)piperidine moiety. The conformations found are in agreement with the required chemical features for kappa affinity and antinociceptive potency.


Asunto(s)
Cristalografía por Rayos X , Piperidinas/química , Receptores Opioides kappa/agonistas , Tetrahidronaftalenos/química , Ligandos , Modelos Moleculares , Conformación Molecular
14.
Acta Crystallogr C ; 45 ( Pt 11): 1797-802, 1989 Nov 15.
Artículo en Inglés | MEDLINE | ID: mdl-2610966

RESUMEN

C21H27NO2, Mr = 325.449, monoclinic, P2(1), a = 16.3916 (7), b = 12.7460 (5), c = 8.9806 (5) A, beta = 107.191 (4) degrees, V = 1792.5 (2) A3, Z = 4, Dm = 1.22 (2), D chi = 1.206 Mg m-3, lambda(Cu K alpha) = 1.54178 A, mu(Cu K alpha) = 0.566 mm-1, F(000) = 704, T = 291 K, final R = 0.048 for 4225 observed reflections. The two molecules present in the asymmetric unit adopt a different conformation with respect to the N-side chain. Starting from the asymmetric carbon and proceeding along the allyl moiety the conformations are antiperiplanar/(-)-anticlinal for molecule 1 and antiperiplanar/(+)-synclinal for molecule 2. The furyl rings engage in aromatic-aromatic interactions which are compared with results from a theoretical study from the literature. Finally, the 3-furyl geometry is evaluated through a Cambridge Structural Database search and CNDO/2 calculations.


Asunto(s)
Benzomorfanos , Endorfinas/antagonistas & inhibidores , Morfinanos , Fenómenos Químicos , Química Física , Conformación Molecular , Estructura Molecular , Difracción de Rayos X
15.
Acta Crystallogr C ; 46 ( Pt 9): 1730-2, 1990 Sep 15.
Artículo en Inglés | MEDLINE | ID: mdl-2088425

RESUMEN

1-(2,3-Dideoxy-3-fluoro-beta-D-erythro-pentofuranosyl)thymine, C10H13FN2O4, Mr = 244.22, monoclinic, P21, a = 6.408 (14), b = 18.716 (26), c = 9.329 (7) A, beta = 98.4 (1) degrees, V = 1107 (3) A3, Z = 4, Dm = 1.46, Dx = 1.465 Mg m-3, graphite-monochromated Mo K alpha radiation, lambda = 0.71073 A, mu = 0.1169 mm-1, F(000) = 512, T = 298 K, final R = 0.035 for 1425 unique observed reflections. The asymmetric unit contains two molecules (A and B). For molecule A: the N-glycosidic torsion angle chi has a value of -138.4 (5) degrees in the anti range; the sugar pucker is 2E with P = 164 (1) degrees and psi m = 36 (1) degrees and the C4'--C5' conformation is +sc with gamma = 50.2 (7) degrees. For molecule B: the N-glycosidic torsion angle chi has a value of -159.6 (5) degrees in the anti range; the sugar pucker is 2T3 with P = 169 (1) degrees and psi m = 32 (1) degrees and the C4'--C5' conformation is + sc with gamma = 52.8 (7) degrees. The conformational parameters are in accordance with the IUPAC-IUB Joint Commission on Biochemical Nomenclature [Pure Appl. Chem. (1983), 55, 1273-1280] guidelines. Base-pair formation occurs between the two molecules A and B.


Asunto(s)
Didesoxinucleósidos/química , Enlace de Hidrógeno , Conformación Molecular , Temperatura , Difracción de Rayos X
16.
Skeletal Radiol ; 11(1): 9-12, 1984.
Artículo en Inglés | MEDLINE | ID: mdl-6584983

RESUMEN

A case of lethal, subacute monocytic leukaemia is described in which the development of multiple sclerotic bone lesions, resembling metastases, was due to secondary myeloid metaplasia. The spectrum of leukaemic involvement of the skeleton is discussed with emphasis on sclerotic bone lesions. The differential diagnosis of other focal areas of bone sclerosis is considered.


Asunto(s)
Neoplasias Óseas/diagnóstico por imagen , Leucemia Mieloide/diagnóstico por imagen , Mielofibrosis Primaria/etiología , Neoplasias Óseas/diagnóstico , Neoplasias Óseas/secundario , Diagnóstico Diferencial , Humanos , Leucemia Mieloide/complicaciones , Masculino , Persona de Mediana Edad , Huesos Pélvicos/diagnóstico por imagen , Mielofibrosis Primaria/diagnóstico , Mielofibrosis Primaria/diagnóstico por imagen , Radiografía , Hombro/diagnóstico por imagen
17.
Acta Crystallogr C ; 46 ( Pt 2): 313-7, 1990 Feb 15.
Artículo en Inglés | MEDLINE | ID: mdl-1970258

RESUMEN

C17H27N3O4S, Mr = 369.48, monoclinic, P2(1)/c, a = 13.333 (7), b = 7.946 (4), c = 17.550 (10) A, beta = 96.99 (4) degrees, V = 1845 (2) A3, Z = 4, Dm = 1.33, Dx = 1.330 Mg m-3, graphite-monochromated Cu K alpha radiation, lambda = 1.54178 A, mu = 1.744 mm-1, F(000) = 792, T = 293 K. Final R = 0.038 for 2405 unique observed reflections. The folded conformation of the molecule with the least-squares planes of the aromatic and the pyrrolidine rings almost perpendicular is essentially determined by intra- and intermolecular hydrogen bonds. In this way, two pseudorings are formed, one linking the amide H with the methoxy O, and a second one involving the 4-amino H and a sulfonyl O. An intermolecular hydrogen bond forces the planar amide group some 28 degrees out of the plane of the aromatic ring.


Asunto(s)
Antipsicóticos , Sulpirida/análogos & derivados , Amisulprida , Conformación Molecular , Difracción de Rayos X
18.
Acta Crystallogr B ; 48 ( Pt 1): 95-103, 1992 Feb 01.
Artículo en Inglés | MEDLINE | ID: mdl-1319719

RESUMEN

C10H15N3O4, Mr = 241.25, orthorhombic, P2(1)2(1)2(1), a = 7.4013 (4), b = 8.7563 (5), c = 17.392 (1) A, V = 1127.1 (1) A3, Z = 4, Dm = 1.42, Dx = 1.422 Mg m-3, Ni-filtered Cu K alpha radiation, lambda = 1.54178 A, mu = 0.895 mm-1, F(000) = 512, T = 293 K, final R = 0.044 for 1024 unique observed [F greater than or equal to 6 sigma (F)] reflections. The conformational parameters are in accordance with the IUPAC-IUB Joint Commission on Biochemical Nomenclature [Pure Appl. Chem. (1983), 55, 1273-1280] guidelines. In order to assess the possible use of pyranosyl-modified pyrimidine nucleosides in the design of new synthetic oligonucleotides, the conformational and packing properties of 13 structures were examined. From this study, it becomes clear that the pyrimidine-base geometry is independent of the sugar ring type (furanosyl- or pyranosyl-like). The bases are always positioned in an equatorial orientation on the pyranoside sugar, which means that the sugar adopts a 4C1 conformation in alpha- and 4C1 in beta-enantiomers. As a result of the anomeric effect the O5'-C1' bond length is 0.020 (4) A shorter than the C5'-O5' distance (C1' is the anomeric C atom). The O5'-C1'-N1-C2 torsion angle chi in the 13 nucleosides is centered around 244 (8) degrees and varies from 196.4 (3) to 287.0 (2) degrees. Molecular-mechanics calculations on uncharged pyranosyl nucleosides are found to be less accurate compared with semi-empirical quantum-chemical methods or molecular-mechanics calculations on charged molecules.(ABSTRACT TRUNCATED AT 250 WORDS)


Asunto(s)
Nucleósidos de Pirimidina/química , Zalcitabina/análogos & derivados , Cristalografía , Conformación de Ácido Nucleico , Difracción de Rayos X , Zalcitabina/química
19.
Acta Crystallogr C ; 56 Pt 11: 1346-7, 2000 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-11077293

RESUMEN

In the title compound, C(28)H(38)N(4)O(6), the 4-aryl substituent occupies a pseudo-axial position approximately orthogonal to the plane of the dihydropyridine ring [88.1 (3) degrees ]. The dihydropyridine ring adopts a flattened boat conformation. The H atom on the pyridine N atom is involved in a bifurcated intramolecular hydrogen bond, the acceptors being the N atoms of the two piperidylmethyl groups [N.N 2.629 (4) and 2.695 (4) A].

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