Academic literature on the topic '4-oxopyrido[2,3-d]pyrimidines synthesis'

An unequivocal set of procedures for the synthesis of 4-amino-1,5,6,8-tetrahydropyrido[2,3-d]pyrimidine-2,7-diones (7) and 2-amino-3,5,6,8-tetrahydropyrido[2,3-d]pyrimidine-4,7-diones (8), in a maximum of four steps from an α,β-unsaturated ester 1, is reported. Thus, the acid hydrolysis of the 2,4-diaminopyrido[2,3-d]pyrimidines 3 yields the 4-amino-2-oxopyrido[2,3-d]pyrimidines 7 while the cyclization of the Michael adducts 9 (formed by reaction of 1 and methyl cyanoacetate) with guanidine affords the corresponding 2-amino-4-oxopyrido[2,3-d]pyrimidines 8. Both isomers were also obtained by hydrolysis of the 4-amino-2-bromo- and 2-amino-4-bromo-5,6-dihydropyrido[2,3-d]pyrimidin-7(8H)-ones 5 and 6, respectively.

Synthesis of certain pyrrole derivatives as antimicro-bial agentsIn an effort to establish new pyrroles and pyrrolo[2,3-d] pyrimidines with improved antimicrobial activity we report here the synthesis andin vitromicrobiological evaluation of a series of pyrrole derivatives. A series of new 2-aminopyrrole-3-carbonitriles (1a-d) were synthesized from the reaction of benzoin, primary aromatic amines and malononitrile, from which a number of pyrrole derivatives (2a-dto5a-d) and pyrrolo[2,3-d]pyrimidines (6a-dto10a, d) were synthesized. Thein vitroantimicrobial testing of the synthesized compounds was carried out against Gram-positive, Gram-negative bacteria and fungi. Some of the prepared compounds, [2-amino-1-(2-methylphenyl)-4,5-diphenyl-1H-pyrrole-3-carbonitriles (1b), 2-amino-3-carbamoyl-1-(3-methylphenyl)-4,5-diphenyl-1H-pyrroles (2b),N-(3-cyano-1-(2-methylphenyl)-4,5-diphenyl-1H-pyrrol-2-yl)-acetamides (3b),N-(3-cyano-1-(3-methylphenyl)-4,5-diphenyl-1H-pyrrol-2-yl)-acetamides (3c), 2-amino-1-(4-methoxyphenyl)-4,5-diphenyl-3-tetrazolo-1H-pyrroles (5d),7-(4-methoxyphenyl)-5,6-diphenyl-7H-pyrrolo [2,3-d]pyrimidin-4(3H)-ones (7d), 7-(3-methylphenyl)-5,6-diphenyl-7H-pyrrolo[2,3-d]pyrimidin-4(3H)-thione (9b) andN-(7-(2-methylphenyl)-5,6-diphenyl-7H-pyrrolo[2,3-d] pyrimidine)-N-aryl amines (10a)] showed potent antimicrobial activity.

Fused pyrimidines, 8,9-dimethyl[1,2,4]triazolo[4,3-c]thieno[3,2-e]pyrimidine 5, 3,8,9-trimethyl[1,2,4]triazolo[4,3-c]thieno[3,2-e]pyrimidine 6, 4-benzylidinehydrazono-5,6 dimethylthieno[2,3-d]pyrimidine 7, 4-[4/-hydroxybenzylidine]hydrazono-5,6-dimethylthi-eno[2,3-d]pyrimidine 8, 4-[4/-tolylidin]hydrazono-5,6-dimethylthieno[2,3-d]pyrimidine 9, 4-[4/-nitrobenzylidine]hydrazono-5-ethyl-6-methylthieno[2,3-d]pyrimidine 10 and 4-[4/-chlorobenzylidine]hydrazono-5-ethyl-6-methylthieno[2,3-d]pyrimidine 11 are prepared in good yield by an initial treatment of 2-amino-4,5-dimethylthiophene-3-carbonitrile 1 with formic acid, affording 5,6-dimethylthieno[2,3-d]pyrimidin-4(3H)-one 2, which is chlorinated with thionyl chloride and then hydrazinated with hydrazine hydrate. Finally hydrazino compound 4 is reacted with formic acid, acetic anhydrate, benzaldehyde, p-hydroxybenzaldehyde, p-toluayldehyde, p-nitrobenzaldehyde and p-chlorobenzaldehyde to give thienotriazolopyrimidines 5-6 and thienopyrimidines 7-11 respectively. All the compounds have been screened for their antimicrobial activity. Keywords: Fused pyrimidines; Hydrazino compound; Thienotriazolopyrmidines; Thienopyrimidines; Antimicrobial activity.© 2009 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved.DOI: 10.3329/jsr.v1i2.2299

In the present study, a series of benzothiazol derivatives 3a-l containing pyrazolo[3,4-d]pyrimidine moiety at the second position were synthesized and characterized by analytical and spectral data. The compounds were tested for their in vitro antimicrobial activity. Compounds 1-(1,3-benzothiazol-2- yl)-3-methyl-4-phenyl-1H-pyrazolo[3,4-d]pyrimidine (3a), 1- (1,3-benzothiazol-2-yl)-4-(4-chlorophenyl)-3-methyl-1H-pyrazolo[ 3,4-d]pyrimidine (3d) and 1-(1,3-benzothiazol-2-yl)- 3-methyl-4-substituted phenyl-1H-pyrazolo[3,4-d]pyrimidines (3h-j) showed significant inhibitory activity against P. aeruginosa whereas compounds 1-(1,3-benzothiazol-2-yl)-4- (2-chlorophenyl)-3-methyl-1H-pyrazolo[3,4-d]pyrimidine (3b), 2-[1-(1,3-benzothiazol-2-yl)-3-methyl-1H-pyrazolo[3,4-d]pyrimidin- 4-yl]phenol (3e), 1-(1,3-benzothiazol-2-yl)-4-(3,4-dimethoxyphenyl)- 3-methyl-1H-pyrazolo[3,4-d]pyrimidine (3h), 4-[1-(1,3-benzothiazol-2-yl)-3-methyl-1H-pyrazolo[3,4-d]pyri midin-4-yl]-N,N-dimethylaniline (3j) and 1-(1,3-benzothiazol- 2-yl)-3-methyl-4-[2-phenylvinyl]-1H-pyrazolo[3,4-d]pyrimidine (3k) were found to be active against C. albicans. Some of these synthesized compounds were evaluated for their in vivo acute toxicity, analgesic, anti-inflammatory, and ulcerogenic actions. The tested compound 4-[1-(1,3-benzothiazol- 2-yl)-3-methyl-1H-pyrazolo[3,4-d]pyrimidin-4-yl]-N, N-dimethylaniline (3j) exhibited maximum analgesic and anti-inflammatory activities. Compounds 1-(1,3-benzothiazol- -2-yl)-3-methyl-4-(3-nitrophenyl)-1H-pyrazolo[3,4-d]pyrimidine (3i) and 3j showed a significant gastrointestinal protection compared to the standard drug diclofenac sodium.

Synthesis of a new 4-hydrazinopyrazolo[3,4- d]pyrimidine was achieved via heating (4,6-dithioxo-1 H-pyrazolo[3,4- d] pyrimidin-3-yl)acetonitrile with hydrazine hydrate. Reactions of the latter product with thiophene-2-carbaldehyde and ethyl hydrazonoacetoacetate analogues afforded the corresponding hydrazone and pyrazole derivatives, respectively. Similarly, condensation of 2-[6-(benzylsulfanyl)-4-hydrazino-1 H-pyrazolo[3,4- d]pyrimidin-3-yl]acetonitrile with thiophene-2-carbaldehyde and ethyl hydrazonoacetoacetate analogues gave the respective hydrazone and pyrazolone derivatives. Alkylation reactions of 2-[4,6-bis(benzylsulfanyl)-1 H-pyrazolo[3,4- d]pyrimidin-3-yl]acetonitrile with arylamines gave the respective 4-( N-arylamino)-6-benzylsulfanylpyrazolo[3,4- d]pyrimidine derivatives.

It is reported on the microwave-assisted synthesis of imidazo- and pyrimidopyrido [4’,3’:4,5]thieno[ 2,3-d]pyrimidines from 2-ethoxymethylene-amino-3-cyano-4,5,6,7-tetrahydrothieno[2,3-c]- pyridine-6-carboxylic acid ethyl ester and 4-chloro-pyridothieno[2,3-d]pyrimidine.

A systematic study of the synthesis of the 5,7-diaryl-4-oxo-pyrazolo[3,4-d]pyrimidin-6-thiones (3), 2-phenyl-5,7-bis(2′-methylphenyl)-4-oxo-pyrazolo[3,4-d]pyrimidin-6-thiones (4b), 2(3H)-3-phenyl-5,7-diaryl-4-oxo-pyrazolo[3,4-d]pyrimidin-6-thiones (5), 5,7-diaryl-4-oxo-isoxazolo[5,4-d]pyrimidin-6-thiones (7), 3,5,7-triaryl-2,3-dihydro-4-oxo-isoxazalo[5,4-d]pyrimidin-6-thiones (8), 2-amino-6,8-diaryl-5-oxo-pyrimido[4,5-d]pyrimidin-7-thiones (9), 3,4-dihydro-2-amino-4-phenyl-6,8-diaryl-5-oxo-pyrimido[4,5-d]pyrimidin-7-thiones (10), 3-cyano-6,8-diaryl-2,5-dioxo-pyrido[2,3-d]pyrimidin-7-thiones (11) from the condensation products 1 and 2, derived from 1,3-diaryl-2-thiobarbituric acids is described.Key words: synthesis, fused, pyrazole, isoxazole, pyrimidines.

Bromination of intermediate 1-[4-(6, 7-dihydro-5H-cyclopenta [4, 5] thieno[2, 3-d]pyrimidin-4-yl amino) phenyl] ethanone(4)yielded(5). Which upon reaction with different substituted benzothiazoles give a novel series of pyrimidine[6(a-g)]. However reaction of(5)with 4-chloro-2-triflouro acetyl aniline provided(6h). Similarly reaction of(5)with 5-amino tetrazole & 2-amino benzimidazole produced(6i)&(6j)respectively. All the synthesized compounds were tested against bacteria (Gram positive and Gram negative).

Several 6-substitued-1-methyl-2,5,7,8-tetrahydro-2-thiopyrimido[4,5-d]pyrimidine-4-ones and ethyl 7-amino-5-aryl-1-methyl-4-oxo-1,2,3,4-tetrahydro-2-thiopyrido[2,3-d]pyrimidines-6-carboxylates were synthesized by treatment of 6-amino-1-methyl-2-thiouracil with primary amines and formalin (40%), and with ethyl 3-aryl-2-cyanoacrylate respectively. 8-Substituted-7-hydroxy-3- methyl-2-thioxanthines were synthesized by the treatment of 6-amino-1-methyl-5-nitroso-2-thiouracil with benzylidene-anilines. Elemental and spectral analyses were performed for the new compounds.

1-(Methyl 2-O-benzyl-4,6-O-benzylidene-3-deoxy-α-D-altropyranosid-3-yl)but-3-yn-2-one (3a) reacted with 3-amino-1H-1,2,4-triazole and 5-aminopyrazole-4-carboxylic acid derivatives in the presence of base to furnish the triazolo[1,5-a]pyrimidine (5) and the pyrazolo[1,5- a]pyrimidines (8a - d), respectively. Treatment of 1-(methyl 2-O-benzyl-4,6-O-benzylidene-3- deoxy-α-D-altropyranosid-3-yl)-4-phenyl-but-3-yn-2-one (3b) with cyanacetamide, 2-cyano-N- (4-methoxyphenyl)acetamide und N-aryl-3-oxo-butyramides afforded the substituted nicotinonitriles (11a - d). Furthermore, reaction of 3b with 2-benzimidazolyl-acetonitrile yielded the benz[4,5]imidazo[1,2-a]pyridine-4-carbonitrile (13). Deprotection of 8d in two steps afforded the 2-amino-N-benzyl-5-(methyl 3-deoxy-α-D-altropyranosid-3-yl-methyl)pyrazolo[1,5-a]pyrimidine- 3-carboxamide (10). Compounds 5 and 11d were treated with AcOH/H2O to furnish the 5-(methyl 2-O-benzyl-3-deoxy-α-D-altropyranosid-3-yl-methyl)[1,2,4]triazolo[1,5-a]pyrimidine (6) and the 3-acetyl-1,2-dihydro-1-(4-methoxyphenyl)-6-(methyl 2-O-benzyl-3-deoxy-α-D-altropyranosid-3-ylmethyl)- 4-phenylpyridin-2-one (12), respectively.

Les Cinases de Proteïna (PKs) estan implicades en processos fonamentals de la regulació del cicle cel•lular. L’acumulació d’anomalies als mecanismes de control i el comportament disfuncional que se’n deriva han estat detectats a cèl•lules de diferents teixits afectades per càncer, desordres immunològics, endocrins, nerviosos, neurodegenaratius, cardiovasculars, malalties infeccioses, diabetis, Alzheimer, asma, restenosi, arteriosclerosi, leucèmia, artritis, etc. Però d’entre totes les PKs, les Cinases de Tirosina (TKs) han estat destacades com a l’element central de tots aquests processos i, per tant, han estat objecte d’una gegantina tasca investigadora que n’ha augmentat el seu innegable interès com a diana terapèutica. És per aquest motiu, que el desenvolupament d’inhibidors selectius de TKs ha esdevingut una àrea d’investigació molt activa. El Laboratori de Síntesi de l’IQS disposa d’una dilatada experiència de síntesi de compostos heterocíclics, especialment pirido[2,3-d]pirimidines, de gran semblança amb coneguts inhibidors de TKs. Malauradament, d’entre tots els building blocks emprats per les estratègies sintétiques desenvolupades, les guanidines (especialment les arilguanidines) sempre han limitat l’espai químic assequible per culpa de la poca diversitat d’aquests reactius comercialment disponibles. Per tant, l’objectiu fonamental d’aquest treball és desenvolupar una metodologia com més genèrica millor que permeti obtenir guanidines i, especialment arilguanidines, i que sigui compatible amb les eines sintètiques disponibles emprades per a l’obtenció massiva de pirido[2,3-d]pirimidines. Amb aquest objectiu s’optimitza un procediment de guanidinació d’amines amb àcid aminoiminometanosulfònic (AIMSOA, acrònim de l’anglès aminoiminomethanesulfonic acid) en metanol procurant acoblar-lo amb la reacció multicomponent de Victory. Desgraciadament els rendiments amb arilguanidines són baixos com a resultat de llur baixa nucleofília, llur degradació causada pel metanol i per la competència amb el dissolvent de reacció. Com a alternativa, s’assagen protocols de condensació de piridones en 1,4-dioxà per tal d’afavorir la nucleofília d’aquestes arilguanidines. Sorprenentment no s’obtenen directament les piridopirimidines sinó uns intermedis que després d’un procés de transposició de Dimroth donen lloc als heterobicicles esperats amb rendiments força superiors als descrits mitjançant altres metodologies. En darrer lloc, es planteja i estudia una nova proposta estratègica alternativa al tradicional plantejament del Laboratori de Síntesi de l’IQS per a la síntesi orientada a diversitat. Aquesta proposta implica la construcció de l’esquelet pirido[2,3-d]pirimidínic, seguida de la seva activació mitjançant bromació i diazotizació, i finalment introducció de la diversitat química desitjada. Arran d’aquest estudi s’ha obtingut i aïllat un intermedi de Wheland bicíclic mai descrit fins ara i que posteriorment és transformat per tractament amb DMSO en un terme piropirimidínic dibromat i deshidrogenat a l’anell piridònic. A més a més, s’han desenvolupat eines sintètiques per obtenir sistemes 4-oxopirido[2,3-d]pirimidínics partint de llurs anàlegs 4-amino, metodologies que són una alternativa molt atractiva de les estratègies ja desenvolupades.<br>Las Quinasas de Proteína (PKs) se hallan implicadas en procesos fundamentales de la regulación del ciclo celular. La acumulación de anomalías en los mecanismos de control y el consiguiente comportamiento disfuncional han sido detectados en células de diferentes tejidos afectadas por cáncer, desórdenes inmunológicos, endocrinos, nerviosos, neurodegenarativos, cardiovasculares, enfermedades infecciosas, diabetes, Alzheimer, asma, restenosis, arteriosclerosis, leucemia, artritis, etc. Pero de entre todas las PKs, las Quinasas de Tirosina (TKs) han demostrado ser un elemento central en todos estos procesos y, por tanto, han atraído sobre sí un enorme esfuerzo investigador que ha remarcado, su innegable interés como diana terapéutica. Así pues, el desarrollo de inhibidores selectivos de TKs se ha convertido en un área muy activa de investigación. El Laboratorio de Síntesis del IQS posee amplia experiencia en la síntesis de compuestos heterocíclicos, en especial pirido[2,3-d]pirimidinas, de gran similitud con inhibidores conocidos de TKs. Ahora bien, de todos los building blocks empleados en las estrategias sintéticas desarrolladas, las guanidinas (especialmente las arilguanidinas) siempre han limitado el espacio químico asequible por la poca diversidad de estos reactivos comercialmente asequibles. Por consiguiente, el objetivo fundamental del presente estudio es desarrollar una metodología para la obtención de guanidinas y, en especial de arilguanidinas, que sea compatible con las herramientas sintéticas disponibles para la obtención masiva de pirido[2,3-d]pirimidinas. A tal efecto se optimiza una guanidinación de aminas con ácido aminoiminometanosulfónico en metanol con vistas a poder acoplarlo con la reacción multicomponente de Victory. Desgraciadamente los rendimientos con arilguanidinas son bajos como consecuencia de su baja nucleofilia, su degradación por efecto del metanol y el efecto competente del disolvente de reacción. Para circunvalar este contratiempo se ensayan reacciones de condensación de piridonas en 1,4-dioxano para favorecer la nucleofilia de estas guanidinas. Sorpredentemente no se obtienen directamente las piridopirimidinas sino unos intermedios que tras un proceso de transposición de Dimroth rinden los heterobiciclos deseados con rendimientos bastante superiores a los referidos para otras metodologías. Por último, se propone y estudia una estrategia alternativa de síntesis orientado a diversidad. En este sentido, se construye el esqueleto pirido[2,3-d]pirimidínico para después activarlo mediante bromación y diazotización, y finalmente introducir la diversidad deseada. Fruto de este estudio se ha obtenido y aislado un intermedio de Wheland bicíclico que posteriormente rinde un término piropirimidínico dibromado y deshidrogenado en el anillo piridónico. Adicionalmente, se han desarrollado herramientas sintéticas para la obtención de sistemas 4-oxopirido[2,3-d]pirimidínicos a partir de sus análogos 4-amino.<br>Protein Kinases (PKs) are involved in basic cellular cycle regulatory mechanisms. Deregulation of those has been found on cells of different tissues with cancer, immunological disorders, endocrine disorders, nervous disorders, neurodegenerative disorders, cardiovascular disorders, infectious diseases, diabetes, Alzheimer syndrome, asthma, restenosis, atherosclerosis, leukemia, arthritis, and more. Among all the PKs huge family, Tyrosine Kinases (TKs) have been described as key point of those regulatory mechanisms and so stated as promising drug targets for treating such diseases. As a result of this biological knowledge, there have been a lot of developments in this field, resulting in some interesting and commercial TKs selective inhibitors. The Laboratori de Síntesi de l’IQS has developed some highly efficient heterocyclic synthetic procedures, especially for the synthesis of pyrido[2,3-d]pyrimidines that are structurally closely related to some well stated TKs inhibitors. Unfortunately, some of the building blocks used in those methodologies have a very narrow commercial variety and are only available from unusual vendors. This is the case for arylguanidines. As a result, the accessible chemical space is shortened. So then, the present work deals with the establishment of general procedures for the synthesis of arylguanidines and how to couple them with our previous described methodologies in order to obtain pyrido[2,3-d]pyrimidine libraries. Aminoiminomethanesulfonic acid (AIMSOA) is selected as guanidination agent and a protocol is optimized by Experimental Design. The coupling of this guanidination with the one-pot multicomponent Victory reaction is also studied. Unfortunately, coupling reaction yields with arylguanidines are very low as a result of lack of nucleophilicity, methanol mediated degradation and nucleophilic competition with this reaction solvent. Pyridone condensation with arylguanidines in 1,4-dioxane is stated as methodological alternative in order to improve nucleophilicity of the arylguanidines. Surprisingly, this procedure does not yield the expected pyridopyrimidines but a family of new, not previously described, heterobicyclic compunds that can be converted to the desired pyridopyrimidines through Dimroth rearrangement. The overall yields for the final pyridopyrimidines are higher with this new procedure than with the previous methodologies. Finally, a new global strategy is developed for the diversity oriented synthesis of 2-arylamino substituted pirido[2,3-d]pyrimidines. Firstly, the heterobicyclic skeleton is build and, secondly, this skeleton is activated by bromination and diazotization. Finally, diversity is introduced by substitution reactions. During this development a pyridopyrimidine Wheland intermediate, never described before ,has been isolated and its structure spectroscopically confirmed. The subsequent treatment of this compound with DMSO yields a new dibrominated pyridopyrimidine dehydrogenated on the pyridone ring. In addition, some synthetic procedures for the conversion of 4-aminopirido[2,3-d]pyrimidines into their 4-oxo analogues have been established. Such methodologies are auseful alternative to our old strategies for the synthesis of this kind of compounds.

Imatinib mesylate is indicated for the treatment of chronic myeloid leukemia (CML) and unresectable and/or metastatic malignant gastrointestinal stromal tumors (GIST). By the application of this anticancer drug, problems occurs in terms of stability and activity. Computer assisted design (CAD) works showed that the modification of the B and C part molecule can increase the effectivity of the drug. The new derivatives of the drug will be obtained to change some part of the B and C segments. The total synthesis of a new imatinib mesylate will be done and the activity tests are going to be determined in collaboration with other groups.

Yuqing Hou of Southern Illinois University found (J. Org. Chem. 2009, 74, 6362) that the peroxy ether 2 served effectively to directly transfer a methoxy group to the lithiated 1 to give 3. Wanzhi Chen of Zhejiang University, Xixi Campus, showed (J. Org. Chem. 2009, 74, 7203) that pyrimidines such as 4, readily prepared from the corresponding phenol, underwent smooth Pd-catalyzed ortho acetoxylation. Trond Vidar Hansen of the University of Oslo observed (Tetrahedron Lett. 2009, 50, 6339) that simple electrophilic formylation of phenols such as 6 also proceeded with high ortho selectivity. Kyung Woon Jung of the University of Southern California optimized (J. Org. Chem. 2009, 74, 6231) the Rh catalyst for ortho C-H insertion, converting 8 into 9. Jin-Quan Yu of Scripps/La Jolla devised (Science 2010, 327, 315) a protocol for carboxy-directed catalytic ortho palladation that allowed subsequent Heck coupling, transforming 10 into 11. Norikazu Miyoshi of the University of Tokushima established (Chem. Lett. 2009, 38, 996) that in situ generated strontium alkyls added 1,6 to benzoic acid 13, to give, after mild oxidative workup, the 4-alkyl benzoic acid 15. Amin Zarei of Islamic Azad University showed (Tetrahedron Lett. 2009, 50, 4443) that their previously developed protocol for preparing stable diazonium silica sulfates could be extended to the preparation of an aryl azide such as 17. Stephen L. Buchwald of MIT developed (J. Am. Chem. Soc. 2009, 131, 12898) a Pd-mediated protocol for the conversion of aryl chlorides to the corresponding nitro aromatics. Virgil Percec of the University of Pennsylvania has also reported (Organic Lett. 2009, 11, 4974) the conversion of an aryl chloride to the borane, and Guy C. Lloyd-Jones has described (Angew. Chem. Int. Ed. 2009, 48, 7612) the conversion of phenols to the corresponding thiols. Kwang Ho Song of Korea University and Sunwoo Lee of Chonnam National University demonstrated (J. Org. Chem. 2009, 74, 6358) that the Ni-mediated homologation of aryl halides worked with a variety of primary and secondary formamides. Kwangyong Park of Chung-Ang University observed (J. Org. Chem. 2009, 74, 9566) that Ni catalysts also mediated the coupling of Grignard reagents with the tosylate 22 not in the usual way but with the C-S bond to give 23.

Numerous enzymes, including those of the hexose monophosphate and glycolytic pathways, are active in the red cell. They are required for the generation of ATP and the reductants NADH and NADPH. 2,3-Diphosphoglycerate, an intermediate of glucose metabolism, is a key regulator of the affinity of haemoglobin for oxygen, and accessory enzymes are also active for the synthesis of glutathione, disposal of oxygen free radicals, and for nucleotide metabolism. With the exception of heavy metal poisoning and rare cases of myelodysplasia, most red cell enzyme deficiency disorders are inherited. They may cause haematological abnormalities, (most commonly nonspherocytic haemolytic anaemias, but also rarely polycythaemia or methaemoglobinaemia, manifest with autosomal recessive or sex-linked inheritance), and may also be associated with nonhaematological disease when the defective enzyme is expressed throughout the body. Some may mirror important metabolic disorders, without producing haematological problems, making them of diagnostic value. Others are of no known clinical consequence. With rare exceptions, it is impossible to differentiate the enzymatic defects from one another by clinical or routine laboratory methods. Diagnosis depends on the combination of (1) accurate ascertainment of the family history; (2) morphological observations—these can determine whether haemolysis is present, rule out some causes of haemolysis (e.g. hereditary spherocytosis and other red blood cell membrane disorders), and diagnose pyrimidine 5′-nucleotidase deficiency (prominent red cell stippling); (3) estimation of red cell enzyme activity; and (4) molecular analysis. The most common red cell enzyme defects are glucose-6-phosphate dehydrogenase deficiency, pyruvate kinase deficiency, glucose-6-phosphate isomerase deficiency, pyrimidine 5′-nucleotidase deficiency—which may also induced by exposure to environmental lead—and triosephosphate isomerase deficiency.