Abstract: 2,4-diaminoquinazoline compounds are inhibitors of the H.sup.+ K.sup.+ ATPase enzyme and useful for the treatment of diseases of the stomach based on excessive gastric acid secretion. A compound of the invention is 2-[2-methyl-4-fluorophenyl)amino]-4-(N-methylphenylamino)quinazoline.

Abstract: This invention pertains to novel substituted N-aryl-N-[4-(1-heterocyclicalkyl)piperidinyl]amides useful as analgesics, and methods of administering analgesia, which comprises the systemic administration to mammals of such compounds, and pharmaceutical compositions containing such compounds, wherein the novel compounds have the general formula: ##STR1## including optically active isomeric forms, and the pharmaceutically acceptable acid addition salts thereof, wherein R, R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are defined in the disclosure.

Abstract: 2,2-Disubstituted 2,3-dihydro-1,4-benzodioxin derivatives of formula (I): ##STR1## and pharmaceutically acceptable salts thereof having in vitro high affinity and selectively for .alpha..sub.1 receptors and in vivo good and long lasting hypotensive activty, with negligible side-effects; processes for the preparation thereof and pharmaceutical compositions therefrom.

Abstract: Anhydrous, stable, crystalline .delta.-form of prazosin hydrochloride, having an infrared spectrum in potassium bromide of FIG. 1 having the following sharp absorption bands at 7.95.mu., 13.3.mu., and a triplet at 9.95.mu. and the x-ray diffractogram of FIG. 2 having sharp bands in 10.5.degree., 12.0.degree., 16.9.degree., and doublets in 24.5.degree. and 26.5.degree.. The .delta.-form of prazosin hydrochloride is prepared by removing the water of crystallization of prazosin hydrochloride hydrate by azeotropic distillation with selected organic solvents having a boiling point in the range of 55.degree.-160.degree. C. The .delta.-form of prazosin hydrochlorie is useful as a hypotensive agent.

Abstract: Compounds of the formula ##STR1## wherein R.sup.1 is H, methyl, ethyl, or chloro and R.sup.2 is hydrocarbyl of 1-12 C are useful as antifungal agents. Compounds of this series wherein R.sup.2 is 7-12 C are novel. A new synthetic method for the compounds is also described.

Abstract: A new anhydrous crystalline form of prazosine hydrochloride characterized by the following bands in the infra-red spectrum in potassium bromide is described:3445 cm.sup.-1 (2.90 .mu.m),1010 cm.sup.-1 (9.90 .mu.m) (duplet), and768 cm.sup.-1 (13.03 .mu.m).This new form is distinguished by its surprisingly great stability in storage compared with known polymorphous forms of prazosine.

Abstract: Quinazoline compounds of the general formula (I): ##STR1## in which (a) R is a hydrogen atom and R.sub.1 is an -(2-pyrrolidinon-1-yl)-alkyl group,(b) R is a methyl group and R.sub.1 is an -(mono- or dialkoxyphenyl)-alkyl group, p0 (c) R together with R.sub.1 forms a piperidine ring substituted with 2-keto-1-benzimidazolinyl radical in the 4-position of the piperidine group ring; or(d) R together with R.sub.1 forms a piperazine ring substituted with a hydroxyacyl group in the 4-position of the piperazine ring.

Abstract: Substituted acylpiperazinoquinazolines of formula I ##STR1## wherein n is 0 or 1, R represents an alkyl group with 1 to 4 carbon atoms or a benzyl group, and R.sub.1 is a hydrogen atom, a methyl group or a phenyl group. Addition salts of these compounds with inorganic and organic acids are also disclosed. The compounds possess a significant antihypertensive activity. They can be prepared by the reaction of 2-halogeno quinazoline derivatives with the corresponding acylpiperazines, followed (if required) by neutralization of the respective base with a suitable acid to form its pharmaceutically convenient addition salt.The acid addition salts, especially hydrochlorides, are readily soluble in water and give stable, almost neutral aqueous solutions which can be used in parenteral (injectable) and peroral medicinal dosage forms.

Abstract: New quinazoline derivatives are disclosed, as represented by the following formula: ##STR1## wherein A is hydrogen atom or lower alkyloxy group; R.sub.4 is hydrogen atom, a lower alkyl, lower alkyloxy or a halogen atom group. Y is hydrogen atom, lower alkyloxy, sulfamoyl or Y and R.sub.4, taken together, are joined to form --O--CH.sub.2 --CH.sub.2 --O--; Z is a 4-oxopiperidino, 4-thioxopiperidino, 4-oximepiperidino, 4-O-loweralkyl-oxime-piperidino, 4-O-(3-lower alkyl-2-hydroxypropyl)-oxime-piperidino, 4-O-(3-lower alkylamino-2-hydroxypropyl)-oxime-piperidino or 4-O-(3-N'-lower alkyl, N'-benzylamino-2-hydroxypropyl)-oxime-piperidino group. These compounds are useful as anti-hypertensive agents.

Abstract: Anhydrous, stable, crystalline .delta.-form of prazosin hydrochloride, having an infrared spectrum in potassium bromide of FIG. 1 having the following sharp absorption bands at 7.95.mu., 13.3.mu. and a triplet at 9.95.mu. and the x-ray diffractogram of FIG. 2 having sharp bands in 10.5.degree., 12.0.degree., 16.9.degree. and doublets in 24.5.degree. and 26.5.degree.. The .delta.-form of prazosin hydrochloride is prepared by removing the water of crystallization of prazosin hydrochloride hydrate by azeotropic distillation with selected organic solvents having a boiling point in the range of 55.degree.-160.degree. C. The .delta.-form of prazosin hydrochloride is useful as a hypotensive agent.

Abstract: An improved process for the preparation of 6-substituted-5-alkyl-2,4-quinazolinediamines, useful in the production of trimetrexate and similar antifolate agents, together with several novel intermediates are disclosed.

Abstract: Quinazoline derivatives having an oxy substituent in 5 and 6 positions are described. The novel quinazoline derivatives are useful as cardiotonic agents.

Abstract: The invention relates to a new multistage process for the production of 4-amino-6,7-dimethoxy-2-[4-(furo-2-yl)-piperazin-1-yl]-quinazoline corresponding to the following formula ##STR1## and physiologically compatible salts thereof, which gives better yields and uses less expensive and more reactive materials than known processes. The intermediate product formed in this process, N"-cyano-N'-(3,4-dimethoxyphenyl)-O-phenylisourea, shows antihypertensive activity on its own.

Abstract: New substituted 1-(4-amino-6,7-dialkoxyquinazolinyl)-4-cyclohexenyl derivatives of piperazine and homopiperazine, of the general formula I ##STR1## in which R.sup.1, R.sup.2, R.sup.3, R.sup.4 and R.sup.5, which can be identical or different, denote hydrogen, straight-chain or branched alkyl groups with in each case 1 to 6 carbon atoms, cyclic aliphatic radicals with in each case 5 to 7 carbon atoms, aromatic radicals or substituted aromatic radicals, which can be monosubstituted or polysubstituted by identical or different substituents from the group comprising halogen and lower alkyl groups with in each case 1 to 4 carbon atoms in the alkyl part, or denote aralkyl radicals, furanyl radicals or thienyl radicals, orR.sup.2 and R.sup.3 together denote the group --(CH.sub.2).sub.a --, wherein a is the number 4 or 5, orR.sup.3 and R.sup.4 together denote the group --(CH.sub.2).sub.b --, wherein b is the number 3, 4 or 5,R.sup.6 and R.sup.

Abstract: There are presented novel quinazoline derivatives, namely 2-(4-substituted-carbamoyl-piperazin-1-yl)quinazoline derivatives, 2-(4-substituted-carbamoyl-homopiperazin-1-yl)quinazoline derivatives, 2-(4-substituted-thiocarbamoyl-piperazin-1-yl)quinazoline derivatives and 2-(4-substituted-thiocarbamoyl-piperazin-1-yl)quinazoline derivatives, having excellent antihypertensive activities.

Abstract: The invention relates to quinazoline derivatives corresponding to the following general formula ##STR1## in which R is a mono- to trisubstituted 5-ring heterocycle from the group comprising triazoles, oxadiazoles, thiazoles and imidazoles, the heterocycle being attached to the piperazine or homopiperazine ring by a carbon atom, and n has a value of 2 or 3, or R represents an N-cyanophenyl imidocarbonate group, and to physiologically compatible salts thereof, to processes for their production and to medicaments containing these compounds.

Abstract: Isobutylene carbonate and certain 1-substituted piperazine compounds are reacted in a process that forms 2-methyl-2-hydroxypropyl 4-substituted piperazine-1-carboxylate compounds which are medicinal agents or synthetic intermediates for such agents. The features of the process allow the preparation of an essentially pure 2-methyl-2-hydroxypropyl carboxylate compound.

Abstract: This invention is directed to new quinazoline derivatives of the following formula having use in the treatment of symptoms associated with allergic manifestations. ##STR1## wherein R.sub.a.sup.1 and R.sub.b.sup.1 are C.sub.2 -C.sub.7 alkoxycarbonyl or R.sub.a.sup.1 and R.sub.b.sup.1 is linked together to form a group of the formula: ##STR2## R.sup.2 and R.sup.3 are hydrogen, C.sub.1 -C.sub.6 alkyl, halogen, nitro, amino, C.sub.1 -C.sub.6 alkoxy, phenoxy, C.sub.1 -C.sub.6 alkylthio, C.sub.1 -C.sub.6 alkylpiperazinyl, C.sub.1 -C.sub.18 alkanoylamino, di(C.sub.1 -C.sub.6)alkanoylamino, C.sub.3 -C.sub.9 alkoxalylamino, C.sub.4 -C.sub.8 cycloalkylcarbonylamino, C.sub.3 -C.sub.7 cycloalkyl(C.sub.1 -C.sub.6)alkanoylamino, benzamido, phenyl(C.sub.1 -C.sub.6)alkanoylamino, C.sub.1 -C.sub.6 alkylsulfonylamino or di(C.sub.1 -C.sub.6)alkylamino which may be substituted with hydroxy,A.sup.1 is a group of the formula: ##STR3## in which R.sup.4 is hydrogen C.sub.1 -C.sub.6 alkyl, hydroxy, C.sub.1 -C.sub.6 alkoxy, C.sub.

Abstract: Compounds of the formula ##STR1## wherein R.sub.1 and R.sub.2, which may be identical to or different from each other, are each independently hydrogen, straight or branched alkyl of 1 to 8 carbon atoms or arylmethyl; orR.sub.1 and R.sub.2, together with each other, are --(CH.sub.2).sub.4 or --(CH.sub.2).sub.5 --; andR.sub.3 and R.sub.4, which may be identical to or different from each other, are each independently hydrogen, straight or branched alkyl of 1 to 4 carbon atoms or arylmethyl; orR.sub.3 and R.sub.4, together with each other, are --CH.sub.3 -- or --CH.sub.2 --CH.sub.2 --;and non-toxic, pharmacologically acceptable acid addition salts thereof. The compounds as well as their salts are useful for the treatment of cardiovascular diseases, especially hypertension.

Abstract: Acylaminoquinazoline derivatives of formula ##STR1## (in which: R.sup.1 represents a lower alkoxy group, a substituted or unsubstituted lower alkyl group, a cycloalkyl group, a lower alkenyl group, a vinyl group having an optionally substituted phenyl or furyl substituent, an optionally substituted phenyl group, a furyl group, an oxazolyl group, a methylthiooxadiazolyl group or a tetrahydrofuryl group;R.sup.2 represents a hydrogen atom or a lower alkyl group;R.sup.3 represents a lower alkyl group or an optionally substituted phenyl group;R.sup.4 represents a hydrogen atom or an acyloxy-substituted phenyl group;X represents a methylene group or a sulphur atom; andn is 2 or 3)and pharmaceutically acceptable acid addition salts thereof are valuable antihypertensive agents and inhibit the activity of the angiotension I-converting enzyme.

Abstract: 4-amino-6,7-dimethoxy-2-(4-phenylalkanoylpiperazin-1-yl) quinazolines having .alpha..sub.1 -adrenergic receptor antagonistic activity. These compounds are useful in the treatment of hypertension.

Abstract: 2,4-Diaminoquinazoline compounds of the formula ##STR1## or a pharmaceutically acceptable salt thereof wherein R is a pyrimidinyl, pyrazinyl, pyridazinyl or triazinyl group linked to the piperazine ring by one of its carbon atoms, and optionally substituted by hydroxy, halogen, alkyl, aralkyl, alkoxy, aralkoxy, alkylthio, aryl, aryloxy and certain amino groups; their use as an antihypertensive agent and pharmaceutical compositions containing them.

Abstract: Quinazoline derivatives of the formulae: ##STR1## wherein A.sup.1 is ##STR2## A.sup.2 is ##STR3## R.sup.1 is hydrogen, carboxy or esterified carboxy, R.sub.a.sup.1 and R.sub.b.sup.1 are esterified carboxy,R.sup.2 and R.sup.3 are hydrogen, alkyl, halogen, nitro, amino, alkoxy, aryloxy, alkylthio, alkylpiperazinyl, acylamino or dialkylamino which may be substituted with hydroxy,R.sup.4 is hydrogen, alkyl, hydroxy, alkoxy, alkenyloxy, dialkylamino or 2,2-dialkoxycarbonylvinylaminoR.sub.a.sup.4 is hydrogen, alkyl, hydroxy, alkoxy, alkenyloxy or dialkylamino,R.sup.5 is alkyl or alkenyl, andR.sup.6 is carboxy or esterified carboxy.

Abstract: Novel piperazinylquinazoline and homopiperazinylquinazoline compounds which have useful antihypertensive activity and their use including pharmaceutical compositions containing said derivatives as the active antihypertensive component thereof. Said compounds have the following formula. ##STR1## wherein m is 2 or 3 and R is as defined in the specification.

Abstract: 2,4-Diaminoquinazolines of the formula ##STR1## wherein Y.sup.1 is hydrogen or chloro, Y.sup.2 is OR, Y.sup.3 is hydrogen or OR such than when Y.sup.1 is hydrogen, Y.sup.3 is OR and when Y.sup.1 is chloro, Y.sup.3 is hydrogen or OR, and the pharmaceutically acceptable salts thereof; R represents an alkyl group having from one to three carbon atoms;taken separately, R.sup.1 and R.sup.2 are each hydrogen, alkyl having from one to five carbon atoms, cycloalkyl having from three to eight carbon atoms, alkenyl or alkynyl each having from three to five carbon atoms or hydroxy substituted alkyl having from two to five carbon atoms, when taken together with the nitrogen atom to which they are attached R.sup.1 and R.sup.2 form a substituted or unsubstituted heterocyclic group optionally containing an atom of oxygen, sulfur or a second atom of nitrogen as a ring member; their use as antihypertensive agents, pharmaceutical compositions containing them and intermediates for their production.

Abstract: Quinazoline derivatives of the formulae: ##STR1## wherein A.sup.1 is ##STR2## A.sup.2 is ##STR3## R.sup.1 is hydrogen, carboxy or esterified carboxy, R.sub.a.sup.1 and R.sub.b.sup.1 are esterified carboxy,R.sup.2 and R.sup.3 are hydrogen, alkyl, halogen, nitro, amino, alkoxy, aryloxy, alkylthio, alkylpiperazinyl, acylamino or dialkylamino which may be substituted with hydroxy,R.sup.4 is hydrogen, alkyl, hydroxy, alkoxy, alkenyloxy, dialkylamino or 2,2-dialkoxycarbonylvinylaminoR.sub.a.sup.4 is hydrogen, alkyl, hydroxy, alkoxy, alkenyloxy or dialkylamino,R.sup.5 is alkyl or alkenyl, andR.sup.6 is carboxy or esterified carboxy.

Abstract: 2,4-Diamino-5-methyl-6-[(3,4,5-trimethoxyanilino)methyl]quinazoline salts, pharmaceutical compositions containing said salts, methods of treating malaria, and bacterial infections employing said salts and compositions and methods for producing said salts.

Abstract: Herein is disclosed 2-(1-piperazinyl)-4-pyrimidinamine derivatives, acid addition salts thereof, processes for their preparation, methods of using the derivatives and pharmaceutical compositions of the derivatives. The derivatives are distinguished most readily by having novel substituents at position 4 of the piperazinyl radical, the substituents being selected from the group consisting of 2-thiazoylyl, oxazolo(4,5-b)pyridin-2-yl and optionally substituted 1-(lower alkyl)-1H-benzimidazol-2-yl. The derivatives are useful for treating hypertension in a mammal.

Abstract: Quinazoline derivatives of the formula (I): ##STR1## R=phenyl which is optionally substituted, furyl, thienyl or 5-alkylthio-1,3,4-oxadiazol-2-yl. These derivatives are useful as drugs, e.g. anti-hypertensive agents.

Abstract: Herein is disclosed 2-(1-piperazinyl)-4-pyrimidinamine derivatives, acid addition salts thereof, processes for their preparation, methods of using the derivatives and pharmaceutical compositions of the derivatives. The derivatives are distinguished most readily by having novel substituents at position 4 of the piperazinyl radical, the substituents being selected from the group consisting of optionally substituted 2-cycloheptimidazolyl, 1,4,5,6,7,8-hexahydrocycloheptimidazol-2-yl, 2-benzoxazolyl, benzthiazol-2-yl, 1H-2-benzimidazolyl and 1-oxo-2,4,6-cycloheptarien-2-yl. The derivatives are useful for treating hypertension in a mammal.

Abstract: Alkylenediamine amides corresponding to the general formula (I) ##STR1## in which R.sub.1 and R.sub.2 each represent, independently of one another, a hydrogen atom, an alkyl having 1 to 4 carbon atoms or the benzyl radical, n is equal to 2, 3 or 4 and R represents either a cycloalkyl radical having 3 to 6 carbon atoms, or a radical ##STR2## in which m is 0, 1 or 2, ##STR3## in which m is 0, 1 or 2 and p is 0, 1 or 2, and also their addition salts with pharmaceutically acceptable acids. These compounds may be prepared by reacting an aminoamide ##STR4## with a 4-amino-2-halogeno-6,7-dimethoxyquinazoline (II). The compounds are useful in treating cardiovascular disorders, and pharmaceutical compositions containing the compounds are also claimed.

Abstract: N-[1-(4-amino-2-quinazolinyl)-3 or 4-piperidinyl]-lactams, e.g., those of the formula ##STR1## and salts thereof are antihypertensive agents.

Abstract: 2,4-Diaminoquinazolines of the formula ##STR1## wherein Y.sup.1 is hydrogen or chloro, Y.sup.2 is OR, Y.sup.3 is hydrogen or OR such that when Y.sup.1 is hydrogen, Y.sup.3 is OR and when Y.sup.1 is chloro, Y.sup.3 is hydrogen or OR, and the pharmaceutically acceptable salts thereof; R represents an alkyl group having from one to three carbon atoms;taken separately, R.sup.1 and R.sup.2 are each hydrogen, alkyl having from one to five carbon atoms, cycloalkyl having from three to eight carbon atoms, alkenyl or alkynyl each having from three to five carbon atoms or hydroxy substituted alkyl having from two to five carbon atoms, when taken together with the nitrogen atom to which they are attached R.sup.1 and R.sup.2 form a substituted or unsubstituted heterocyclic group optionally containing an atom of oxygen, sulfur or a second atom of nitrogen as a ring member; their use as antihypertensive agents, pharmaceutical compositions containing them and intermediates for their production.

Abstract: A series of novel 4-amino-6,7-di(lower alkoxy)-2-(4-substituted piperazino)quinazoline derivatives have been prepared, including their pharmaceutically acceptable acid addition salts. These derivatives all possess a benzo-oxacycloalkanoyl moiety located at the 4-position of the piperazine ring. Such compounds are useful in therapy as highly potent antihypertensive agents. 4-Amino-2-[4-(chroman-2-carbonyl)piperazino]-6,7-dimethoxyquinazoline represents a typical and preferred member compound. Methods for preparing all these compounds from known starting materials are provided and the principal synthetic route leading to the desired final products is described in some detail.

Abstract: An improved method is disclosed for producing antihypertensively active 6,7-dimethoxy-4-amino-2-[4-(2-furoyl)-1-piperazinyl] quinazoline hydrochloride, viz prazosine hydrochloride, by reacting methyl-N-(3,4-dimethoxy-6-cyano-phenyl)-[4-(2-furoyl)-1-piperazinyl]thiofo rmamidate with a large excess of ammonium chloride.

Abstract: Compounds of the formula ##STR1## wherein R.sup.1,R.sup.2,R.sup.3 and R.sup.4 are as hereinafter described, tautomers and salts thereof, are disclosed. The foregoing compounds inhibit the aggregation of blood platelets which renders them useful as therapeutic agents in the prophylaxis of thromboses. Furthermore, they are useful for the treatment and prophylaxis of cardiac insufficiency and cardiac failure, due to their inotropic activity without substantial tachycardia.

Abstract: N-[1-(4-amino-2-quinazolinyl)-3- or 4-piperidinyl]-lactams, e.g., those of the formula ##STR1## and salts thereof are antihypertensive agents.

Abstract: An improved anti-hypertensive agent, the hydrochloride salt of 1-(4-amino-6,7-dimethoxy-2-quinazolinyl)-4-(2-tetrahydrofuroyl)piperazine dihydrate.

Abstract: Regulators of the cardiovascular system and, in particular, in the treatment of hypertension having the formula ##STR1## wherein R is lower alkyl;X, is a 3- or 4-position substituent and is --(CH.sub.2).sub.n CONR.sup.1 R.sup.2, --O(CH.sub.2).sub.n CONR.sup.1 R.sup.2 or ##STR2## wherein n is 0, 1 or 2;R.sup.1 is hydrogen or lower alkyl, andR.sup.2 is lower alkyl; lower alkenyl, lower alkynyl, phenyl, substituted phenyl, C.sub.3 -C.sub.7 cycloalkyl; lower alkyl substituted by phenyl, substituted phenyl, C.sub.3 -C.sub.7 cycloalkyl, halogen, trifluoromethyl, hydroxy, lower alkoxy, lower alkoxycarbonyl, phenoxy, substituted phenoxy or --NR.sup.3 R.sup.4 wherein R.sup.3 and R.sup.4 each represent hydrogen, lower alkyl, lower alkanoyl or lower alkylsulfonyl; with the proviso that any O, N or halogen atom in R.sup.2 is separated by at least 2 carbon atoms from the nitrogen atom to which R.sup.2 is attached; orR.sup.1 and R.sup.

Abstract: Regulators of the cardiovascular system and, in particular, in the treatment of hypertension having the formula ##STR1## pharmaceutically-acceptable bioprecursors thereof, and the pharmaceutically-acceptable acid addition salts thereof; wherein each of R.sup.1 and R.sup.2 is C.sub.1-4 alkyl or --CH.sub.2 CF.sub.3 ; alk is ethylene, monophenyl substituted ethylene, mono- and dimethyl substituted ethylene or monophenylmonomethyl substituted ethylene; and R.sup.3 is hydrogen, C.sub.1-4 alkyl, C.sub.3 -C.sub.6 cycloalkyl; phenyl or substituted phenyl; and methods for their preparation.

Abstract: Quinazoline compounds of the formula: ##STR1## wherein A is ##STR2## wherein n is an integer of 1 or 2, or ##STR3## wherein X is O or CH.sub.2, and n and m are independently an integer of 1 or 2, and its non-toxic pharmaceutically acceptable salts, having an excellent antihypertensive activity without causing adverse effects such as orthostatic hypotension.

Abstract: Compounds having the formula ##STR1## and pharmaceutically acceptable salts thereof wherein R represents 6,7-di(lower alkoxy) or 6,7,8-tri(lower alkoxy);m is 1 or 2,X is --CHR.sup.1 -- or --CH.sub.2 CH.sub.2 --;each R.sup.1 and R.sup.0 may be the same or different and is hydrogen or lower alkyl;each of R.sup.2 and R.sup.3 is hydrogen, lower alkoxy, lower alkyl, halogen, lower alkanoyl, lower alkoxycarbonyl, --CONR.sup.4 R.sup.5 or --SO.sub.2 NR.sup.4 R.sup.5 wherein each of R.sup.4 and R.sup.5 is hydrogen or lower alkyl;processes for their preparation; and their use as regulators of the cardiovascular system, and particularly in the treatment of hypertension.

Abstract: Novel cyanocarboxamidines are disclosed. The new cyanocarboxamidines are particularly valuable as intermediates in the preparation of antihypertensive 4-amino-2-(4-substituted-piperazin-1-yl)-quinazolines.

Abstract: (2-Amino-4-quinazolinyl)-quanidines of the formula ##STR1## wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5 and n have the defined meanings, and their physiologically tolerable acid addition salts, process for preparing these compounds, pharmaceutical preparations containing them and their use as medicines.

Abstract: A series of novel 4-amino-2-(thiadiazole-carbonyl piperazinyl)-6,7-dimethoxyquinazolines is disclosed having antihypertensive properties. The thiadiazole substituent may be optionally substituted with alkyl or lower alkoxy carbonylamino groups. A representative embodiment of the invention is 4-amino-6,7-dimethoxy-2-[4-(5-ethoxy-carbonylamino-1,2,3-thiadiazole-4-car bonyl)-piperazin-1-yl]-quinazoline.

Abstract: The invention relates to novel and valuable crystalline forms of the hypotensive agent prazosin hydrochloride. The anhydrous .alpha.-form is preferred because it is relatively non-hygroscopic and hence possesses important advantages in handling and formulation. The polyhydrate form of prazosin hydrochloride is preferred because of its low, uniform rate of dissolution.