Abstract: There is disclosed an advantageous mixed acid anhydride production method of formula (1): R1C(O)OY(O)n(R2)p  (1) wherein R1, R2 and Y denote the same as defined below, n and p denote an integer of 1 or 2, which is characterized by adding a carboxylic acid of formula (2); R1COOH  (2) wherein R1 denotes a hydrogen atom, an optionally substituted alkyl group or the like, an organic base to a solution of a carboxylic acid activating agent of formula (3); (R2)pY(O)nX  (3) wherein R2 denotes an optionally substituted aliphatic hydrocarbyl group or the like, Y denotes a carbon atom, a phosphorus atom, or a sulfur atom, and X denotes a chlorine atom or the like.

Abstract: This invention provides compounds having the structure wherein A is OR5, or R1 is alkyl, cycloalkyl of 3-8 carbon atoms, thienyl, furyl, pyridyl, R2 is H, alkyl, or aryl; R3 and R4 are halo, H, alkyl, aryl, trifluoromethyl, alkoxyaryl, nitro, amino, carboalkoxy, carbamide, carbamate, urea, alkylsulfonamide, —NR7(CH2)mCO2H, arylsulfonamide, cycloalkyl, or a heterocycle; R5 is H, alkyl, —CH(R8)R9, —CH2(CH2)nCO2R10, —C(CH3)2CO2R10, —CH(R8)(CH2)nCO2R10, —CH(R8)C6H4CO2R10, or —CH2-tetrazole; R6 is H, alkyl, halo, alkoxy, trifluoroalkyl or trifluoroalkoxy; R7 is H or alkyl; R8 is H, alkyl, aryl, arylalkyl, cycloalkyl, phthalic acid, R9 is CO2R12, CONHR12, tetrazole, or PO3R12; R10 is H, alkyl, aryl, or aralkyl; R11 is alkyl; R12 is H, alkyl, aryl, or aralkyl; X is O, or S; Y is O, N, or S; Z is C, or N; Q is O, N, or S; m=1-3; n=1-6, or a pharmaceutically acceptable salt thereof, which

Abstract: Compounds of the formula I are suitable for the production of pharmaceuticals for the prophylaxis and therapy of disorders in the course of which an increased activity of matrix-degrading enzymes is involved.

Abstract: The invention encompasses the novel class of compounds represented by the formula below, which are inhibitors of the PTP-1B enzyme. The invention also encompasses pharmaceutical compositions and methods of treating or preventing PTP-1B mediated diseases, including diabetes.

Abstract: Compounds of formulae I and Ia, wherein X1 is secondary phosphino; R3 is hydrogen, a hydrocarbon radical having from 1 to 20 carbon atoms, a heterohydrocarbon radical, bonded via a carbon atom, having from 2 to 20 atoms and at least one hetero atom selected from the group O, S and NR, or ferrocenyl; R is H or C1-C4alkyl; each R4 individually or both R4 together are a hydrocarbon radical having from 1 to 20 carbon atoms; and R01 and R02 are each independently of the other a hydrogen atom or a hydrocarbon radical having from 1 to 20 carbon atoms, are chiral ligands for metal complexes with metals of sub-groups I and VII, which are catalysts for asymmetric addition reactions, for example of hydrogen, to prochiral unsaturated organic compounds.

Abstract: FBPase inhibitors of the formula I and X are useful in the treatment of diabetes and other conditions associated with elevated blood glucose or excess glycogen storage.

Abstract: The invention encompasses the novel class of compounds represented by formula I, which are inhibitors of the PTP-1B enzyme. The invention also encompasses pharmaceutical compositions and methods of treating or preventing PTP-1B mediated diseases, including diabetes, obesity, and conditions related to diabetes.

Abstract: Novel bisamidate phosphonate prodrugs of FBPase inhibitors of the Formula IA: 1

Abstract: Novel phosphine oxazoline ligands of formula (I) wherein m is 1, 2, 3 or 4; n, p, q, r are independently zero or 1 provided that at least one of n, p, q and r is 1; X is O, S, Se, CH2, NH; Y is N, P, As, S; R is H; a straight, branched or cyclo alkyl optionally substituted by one or more groups independently selected from alkyl, aryl, halo, alkoxy, amine, phosphine, ether; aryl optionally substituted by one or more groups independently selected from alkyl, aryl, halo, alkoxy, amine, phosphine, ether; ferrocenyl; a thioalkyl group; a thioaryl group; or R is part of a polymeric structure, for example polyacrylic acid; R1 to R13 are independently selected from H; a straight, branched or cyclo alkyl optionally substituted by one or more groups independently selected from alkyl, aryl, halo, alkoxy, amine, phosphine, ether; aryl optionally substituted by one or more groups independently selected from alkyl, aryl, halo, alkoxy, amine, phosphine, ether; a process for the preparation thereof,

Abstract: Thiochromanoylpyrazolone derivatives of the formula I where: A is an unsubstituted or substituted, saturated or unsaturated alkyl chain; R1 is cyano, thiocyanato, nitro, OR4, SR5, SOR6, S02R6, ONR6NR7, ON═CR6R8, NR9R10, P(O)R11R12, P(S)R11R12, COR, CO2R6, unsubstituted or substituted phenyl or heterocyclyl; R2 is alkyl, haloalkyl, alkoxy or haloalkoxy; R3 is hydrogen, alkyl or halogen; X is oxygen, sulfur, S═O, S(═O)2, CR13R14, C═O or C═NR15; m is 0, 1 or 2; n is 0, 1, 2, 3 or 4; R16 is substituted pyrazol-4-yl-carbonyl or substituted (4,5-dihydro-5-oxo-pyrazol-4-yl)methylidene; and their agriculturally useful salts; Processes for preparing the thiochromanoylpyrazolone derivatives, compositions comprising them, and the use of these derivatives or of the compositions comprising them for controlling undesirable plants are described.

Abstract: Objects of the present invention are compounds of a peptido-mimetic character having the capacity of acting as inhibitors of metalloproteinases produced by venom of snake, and of other metalloproteinases of human origin which have been put in relation with various pathologies in man, including tumoral growth and metastatization, aterosclerosis, multiple sclerosis, Alzheimer's disease, osteoporosis, hypertension, rheumatoid arthritis and other inflammatory diseases. Object of the present invention is also the procedure for the production of diethylester of (1)-phosphotryptophan, as an initial product necessary to synthesize all compounds mentioned above.

Abstract: Novel intermediates useful in the preparation of optically active H3 histamine receptor antagonist 2-(4-imidazoyl)-cyclopropyl derivatives are disclosed.

Abstract: Novel compounds are provided which are inhibitors of MTP and thus are useful for lowering serum lipids and treating atherosclerosis and related diseases, and have the structure including pharmaceutically acceptable salts thereof, or prodrug esters thereof, A is where Z is N or CH, or where Z is  or CH2 when is a single bond; and wherein L1, R, R1, R3, R3′, R3a, R3b, R4, R4′, R5, R5a, X,  are as defined herein.

Abstract: Compounds of the formula in which R1 and R2 are as defined in the specification, and non-toxic metabolically labile ester and amides thereof are useful as modulators of metabotropic glutamate receptor function.

Abstract: A process for producing phosphinopyrrolidine compounds especially useful for preparing optically active compounds through asymmetric synthesis which is a simplified short process requiring neither a step necessitating a high-temperature and high-pressure reaction nor special equipment for production. A phosphino group is incorporated into a pyrrolidine compound in the presence of a boron compound, and the resultant pyrrolidine compound is further reacted while protecting the phosphorous atom, whereby a dicyclohexylphosphino group can be efficiently incorporated into the pyrrolidine nucleus in the 4-position. Thus, the target phosphinopyrrolidine compounds useful as ligands for asymmetric synthesis catalysts can be obtained through a significantly small number of steps without resort to troublesome steps such as the step of reducing a phenyl group at high temperature and high pressure.

Abstract: The invention encompasses the novel class of compounds represented by formula I which are inhibitors of the PTP-1B enzyme. The invention also encompasses pharmaceutical compositions and methods of treating or preventing PTP-1B mediated diseases.

Abstract: Pyrazole, pyrrole and imidazole derivatives having formula (I) or (II): ##STR1## wherein .dbd.X is .dbd.NR.sup.3, .dbd.O or an electron pair and Q comprises certain pyrazole, pyrrole and imidazole structures which, together with the remaining substituents, are defined in the description, are useful for controlling arthropod, nematodes, helminth or protozoan pests.

Abstract: A compound of the formula ##STR1## in which Ra represents an -alk-COOalk' radical, a --CH.sub.2 --PO(Oalk).sub.2 radical, a --CH.dbd.CH--COOalk' radical or a phenyl radical substituted with an alkoxycarbonyl radical.

Abstract: Chiral diphosphines are constituted by an aromatic pentatomic biheterocyclic system, suitable to act as chiral ligands and complexes between the diphosphines and transition metals. They may be utilized as chiral catalysts in stereocontrolled reactions, such as diastereo- and enantioselective reduction reactions. Process is for the preparation of these chiral diphosphines; and process is for the preparation of these complexes and for their utilization as chiral catalysts in stereocontrolled reactions.

Abstract: The present invention relates to novel 1-sulfonyl-3-phenylpyrazoles of the formula I ##STR1## and agriculturally useful salts of I.

Abstract: A phosphonic diester derivative represented by the following formula (1): ##STR1## wherein R.sup.1 represents a cycloalkyl group; a phenyl group which may have 1 to 3 substituents selected from the group consisting of a lower alkoxy group, a lower alkyl group, a halogen atom, a halogen-substituted lower alkyl group, a lower alkanoyl group, a nitro group, a benzoyl group, a cyano group, an N-lower alkylcarbamoyl group, an N-phenyl-lower alkylcarbamoyl group, an N-(halogen-substituted phenyl)carbamoyl group and an N,N-di-lower alkylcarbamoyl group; a 1,3,4-thiadiazol-2-yl group having a halogen-substituted lower alkyl group as a substituent; a thiazolyl group; a pyridyl group which may be substituted by a halogen atom; a benzothiazol-2-yl group having 1 to 2 lower alkoxy groups on the phenyl ring; or a 4,5-dihydrothieno[3,2-e]benzothiazol-2-yl group; R.sup.2 represents a hydrogen atom or a phenyl lower alkyl group; R.sup.3 and R.sup.

Abstract: Novel compounds are provided which are inhibitors of MTP and thus are useful for lowering serum lipids and treating atherosclerosis and related diseases, and have the structure ##STR1## including pharmaceutically acceptable salts thereof, or prodrug esters thereof,A is ##STR2## where Z is N or CH, or where Z is ##STR3## or CH.sub.2 when --- is a single bond; Q is (1)--O--;(2)--S--; or ##STR4## B is: ##STR5## and wherein L.sup.1, R, R.sup.1, R.sup.3, R.sup.3 ', R.sup.3a, R.sup.3b, R.sup.4, R.sup.4 ', R.sup.5, R.sup.5a, X, ##STR6## are as defined herein.

Abstract: The present invention discloses peptide aldehydes having a lactam group as part of the peptide backbone and having an original mimic group such as an amidinopiperidine or amidinophengyl tail. These compounds are potent and specific inhibitors of thrombin, their pharmaceutically acceptable salts, pharmaceutically acceptable compositions thereof, and methods of using them as therapeutic agents for disease states in mammals characterized by abnormal thrombosis.

Abstract: A herbicidal compound of formula (I) ##STR1## or a salt, tautomer or cyclic derivative thereof; where R.sup.1 and R.sup.2 are hydrogen and A is an optionally substituted saturated or unsaturated chain or ring of three carbon atoms.Methods for preparing these compounds, intermediates used in the preparation and herbicidal compositions containing them are also described and claimed.

Abstract: The invention is concerned with a new process for the preparation of compounds of formula ##STR1## wherein R.sup.1 is trityl, acetyl, tetrahydropyranyl or cyclopentyl;R.sup.2 is hydrogen, hydroxy, lower alkyl, cycloalkyl, lower alkoxy, lower alkenyl, lower alkynyl, aryl, aryloxy, aryl-lower alkyl, aryl-lower alkoxy or heterocyclyl or heterocyclyl-lower alkyl; the lower alkyl, cycloalkyl, lower alkoxy, lower alkenyl, cycloalkenyl, lower alkynyl, aryl-lower alkyl, aryl, aryloxy, aryl-lower alkoxy, the heterocyclyl moieties being unsubstituted or substituted with at least one group selected from carboxy, amino, nitro, cyano, lower alkyl, lower alkoxy, hydroxy, halogen, --CONR.sup.21 R.sup.22, --N(R.sup.22)COOR.sup.23, R.sup.22 CO--, R.sup.22 OCO-- or R.sup.22 COO--, wherein R.sup.21 is hydrogen, lower alkyl, or cycloalkyl; R.sup.22 is hydrogen or lower alkyl; R.sup.23 is lower alkyl, lower alkenyl or a carboxylic acid protecting group;Y is --S-- and Z is --CH.sub.2 -- orY is --CH.sub.

Abstract: The present invention relates particularly to novel preorganized hexadentate ligands that are suitable for completing with a radionuclide, and are useful as general imaging agents for diagnostic purposes.

Abstract: The invention is concerned with a new process for the preparation of compounds of formula ##STR1## wherein R.sup.1 is trityl, acetyl, tetrahydropyranyl or cyclopentyl;R.sup.2 is hydrogen, hydroxy, lower alkyl, cycloalkyl, lower alkoxy, lower alkenyl, lower alkynyl, aryl, aryloxy, aryl-lower alkyl, aryl-lower alkoxy or heterocyclyl or heterocyclyl-lower alkyl; the lower alkyl, cycloalkyl, lower alkoxy, lower alkenyl, cycloalkenyl, lower alkynyl, aryl-lower alkyl, aryl, aryloxy, aryl-lower alkoxy, the heterocyclyl moieties being unsubstituted or substituted with at least one group selected from carboxy, amino, nitro, cyano, lower alkyl, lower alkoxy, hydroxy, halogen, --CONR.sup.21 R.sup.22, --N(R.sup.22)COOR.sup.23, R.sup.22 CO--, R.sup.22 OCO-- or R.sup.22 COO--, wherein R.sup.21 is hydrogen, lower alkyl, or cycloalkyl; R.sup.22 is hydrogen or lower alkyl; R.sup.23 is lower alkyl, lower alkenyl or a carboxylic acid protecting group;Y is --S-- and Z is --CH.sub.2 -- orY is --CH.sub.

Abstract: The present invention relates to thio-substituted, nitrogen-containing heterocyclic phosphonate compounds, including bisphosphonates, phosphonoalkylphosphinates, phosphonocarboxylates, and phosphonosulfonates, and the pharmaceutically-acceptable salts and esters thereof useful for the treatment and prevention of osteoporosis and arthritis. These compounds have the general structure: ##STR1## (a) Z is a monocyclic or polycyclic heterocyclic ring moiety containing one or more heteroatoms selected from O, S, or N, at least one of which is N;(b) Q is covalent bond; O, S, N, or NR.sub.1 ;(c) R is COOH, SO.sub.3 H, PO.sub.3 H.sub.2, or P(O)(OH)R.sup.4, wherein R.sup.4 is substituted or unsubstituted C.sub.1 -C.sub.8 alkyl;(d) each R1 is independently selected from --SR.sup.6 ; --R.sup.8 SR.sup.6 ; nil; hydrogen; unsubstituted or substituted C.sub.1 -C.sub.8 alkyl; unsubstituted or substituted aryl; hydroxy; --CO.sub.2 R.sup.3 ; --O.sub.2 CR.sup.3 ; --NR.sup.3.sub.2 ; --OR.sup.3 ; --C(O)N(R.sup.3).sub.2 ; --N(R.sup.

Abstract: Compounds of general formula I and their salts and solvates are angiotensin II receptor antagonists and as such are useful in the treatment of hypertension, congestive heart failure and elevated intraocular pressure. Pharmaceutical compositions including these compounds and processes for their preparation are also provided.

Abstract: A compound having the formula (I), a physiologically tolerable salt of the compound having the formula (I) and/or a steroisomeric form of the compound having the formula (I), in which one residue R.sup.1 or R.sup.2 stands for the formula (II), are suitable for preparing medicaments for the therapy of inflammations, asthma, rheumatoid diseases and auto-immune diseases.

Abstract: The present invention relates to quaternary nitrogen-containing phosphate compounds, and the pharmaceutically-acceptable salts and esters thereof having the general structure: ##STR1## wherein: Z is a saturated, unsaturated, or aromatic, monocyclic or polycyclic carbocycle or monocyclic or polycyclic heterocycle containing one or more heteroatoms selected from O, S, or N;Y is N.sup.+ (R.sup.8).sub.2 or C(R.sup.1).sub.2 and when Y is C(R.sup.1).sub.2, at least one R.sup.2 must be N.sup.+ (R.sup.8).sub.3 ;R.sup.1, R.sup.2, R.sup.5, and R.sup.8 are defined in claim 1, m and n are integers from 0 to 10; m+n is from 0 to 10;R is COOH; PO.sub.3 H.sub.2 ; SO.sub.3 H; or P(O)(OH)R.sub.4, wherein R.sub.4 is substituted or unsubstituted alkyl of 1-8 carbons atoms.The present invention further relates to pharmaceutical compostions containing a safe and effective amount of a compound of the present invention, and pharmaceutically-acceptable excipients.

Abstract: New nitrones which are usable for the scavaging of free radicals, are selected from 5-diethoxyphosphoryl-5-methyl-1-pyrroline 1-oxide, 5-phosphono-5-methyl-1-pyrroline 1-oxide, and 5-diethoxyphosphoryl-5-methyl-(2,3,3-.sup.2 H.sub.3)-1-pyrroline 1-oxide, as well as its corresponding physiologically acceptable salts obtained by the action of an inorganic or organic base.

Abstract: This invention relates to 3-aryl-2-isoxazoline compounds which are selective inhibitors of phosphodiesterase type IV (PDE.sub.IV). The 3-aryl-2-isoxazolines are useful in the treatment of AIDS, asthma, arthritis, bronchitis, chronic obstructive pulmonary disease, psoriasis, allergic rhinitis, dermatitis, shock, atopic dermatitis, rheumatoid arthritis and osteoarthritis. This invention also relates to pharmaceutical compositions useful therefor.

Abstract: A phospholipid derivative of the following formula (I): ##STR1## wherein A is a residue of a phospholipid having a phosphatidylethanolamine moiety, and B is a linking group having a polyalkylene glycol moiety.

Abstract: The present invention relates to herbicidal ribofuranose derivatives, particularly hydantocidin derivatives, compositions comprising said derivatives and methods of use.

Abstract: The present invention relates to novel, therapeutically active fatty alkyl and alkenyl ether glycerophospholipids bearing a 3-(2-imidazolinyl)-2-imidazolinyl or 2-imidazolinyl substituent on the ethanolamine nitrogen, methods of using the compounds and pharmaceutically acceptable salts thereof, and pharmaceutical compositions containing same. The novel, therapeutically active compounds and salts of the invention possess anti-tumor, anti-psoriatic, anti-inflammatory, and anti-asthma activities.

Abstract: The invention concerns diazapentalene derivatives of formula I ##STR1## in which X and Y represent leaving groups which are less nucleophilic than thiol compounds, as thiol-specific fluorochromes for the detection of compounds containing thiol groups, in particular in cells.

Abstract: The present invention relates to novel compounds useful for the treatment and prophylaxis of degenerative bone disorders and to the preparation thereof. These compounds are particularly characterized by two active moieties, the first of which possesses "bone-seeking" affinity and the second which is an inhibition of the enzyme carbonic anhydrase and/or an inhibitor of bone resorption. The novel compounds of this invention can be administered as pharmaceutically acceptable compositions and in convenient dosage unit form in a method for the treatment and prophylaxis of degenerative bone disorders.

Abstract: The invention relates to a process of making a compound of the formula ##STR1## wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 and n are as described herein, and, when R.sub.1 is different from R.sub.2, and/or when R.sub.3 is different from R.sub.4, enantiomers, diastereomers and racemates thereof, and salts thereof with pharmaceutically acceptable bases. The method comprises reacting a compound of the formula ##STR2## wherein R.sub.5 and n are as described herein with a compound of the formula ##STR3## to produce a compound of the formula ##STR4## wherein n is as described herein, and converting a compound of formula IV to a compound of formula I.

Abstract: There is provided a squalene inhibitory composition containing a 1,1-bisphosphonic acid compound, a lower alkyl ester thereof, or a salt thereof, which is useful for treating hypercholesterolemia. There are also provided novel compounds having squalene synthetase inhibitory activity and a pharmaceutical composition for treating hypercholesterolemia containing a 1,1-bisphosphonic compound, a lower alkyl ester thereof or a salt thereof.

Abstract: The invention relates to new 1H-3-aryl-pyrrolidine-2,4-dione derivatives of the formula (I) ##STR1## in which A, B, X, Y and G have the meanings given in the description, to a plurality of processes for their preparation, and to their use as pesticides.

Abstract: The present invention relates to the phosphono-alkylamino-substituted tetrazole derivatives of formula I ##STR1## and tautomers thereof wherein R.sub.1 is (carbocyclic or heterocyclic) aryl-C.sub.1 -C.sub.4 -alkyl; X is phenylene, phenylene substituted by lower alkoxy, lower-alkyl, halogen or trifluoromethyl or X.sub.1 is ethynylene; R.sub.2 is carbocyclic or heterocyclic aryl; pharmaceutically acceptable mono- or di-ester derivatives thereof in which one or both of the acidic hydroxy groups of the phosphono functional group are esterified in form of a pharmaceutically acceptable mono- or di-ester, and pharmaceutically acceptable salts thereof; pharmaceutical compositions comprising said compounds; methods for preparation of said compounds and for the preparation of intermediates; and methods of treating disorders in mammals which are responsive to the inhibition of endothelin-converting enzyme by administration of said compounds to mammals in need of such treatment.

Abstract: A phospholipid derivative of the following formula (I): ##STR1## wherein A is a residue of a phospholipid having a phosphatidylethanolamine moiety, and B is a linking group having a polyalkylene glycol moiety.

Abstract: 3-Phenylpyrrolidine compounds of the formula ##STR1## effectively inhibit phosphodiesterase (PDE) IV activities and can be used as medicaments for conditions such as asthma.

Abstract: This invention relates to substituted bicyclic phosphoramides and derivatives thereof, useful as retroviral protease inhibitors and as standards and reagents in determining the ability of a potential pharmaceutical to inhibit viral replication or HIV protease, to pharmaceutical compositions comprising such compounds, and to methods of using these compounds for treating viral infection.

Abstract: Antipsychotics and ischemic cerebral disease therapeutics comprising as an effective ingredient a compound represented by the following formula (1) or (2): ##STR1## or a salt thereof. These drugs do not induce extrapyramidal side effects.

Abstract: Process for the preparation of optically active 4-(phosphinoethyl)-1,3-oxazolidin-5-one derivatives.The invention relates to a process for preparing optically active compounds of formula (IV) ##STR1## in which the radicals R.sub.1, R.sub.2, R.sub.3 ', R.sub.7, n and m are as defined in the main claim,which comprises reacting a compound of formula (II) ##STR2## with a compound of formula (III) ##STR3## in the presence of catalytical amounts of a radical former.

Abstract: The present invention relates to a novel reactive thiophosphate derivative of thia(dia)zole acetic acid which can be very effectively used in the preparation of .beta.-lactam antibiotics, and which is represented by the following general formula (I): ##STR1## in which R.sup.1 represents hydrogen or an amino-protecting group;R.sup.2 represents hydrogen, C.sub.1 -C.sub.4 alkyl, or --C(R.sup.a)(R.sup.b)CO.sub.2 R.sup.c, wherein R.sup.a and R.sup.b are identical or different from each other and represent hydrogen or C.sub.1 -C.sub.4 alkyl, or R.sup.a and R.sup.b together with a carbon atom to which they are bound can form a C.sub.3 -C.sub.7 cycloalkyl group and R.sup.c is hydrogen or a carboxy-protecting group;R.sup.3 represents C.sub.1 -C.sub.4 alkyl or phenyl or R.sup.3 together with an oxygen atom and a phosphorus atom to which it is bound can form a 5- or 6-membered heterocyclic ring; andQ represents N or CH, and to a process for preparing the same.

Abstract: Novel naphthyl-substituted .alpha.-amino acid derivatives, pharmaceutical compositions containing the same and a method of using the same, for the blockade of aspartate and glutamate receptors, are described. Novel intermediates of the napthyl-substituted .alpha.-amino acid derivatives are disclosed.

Abstract: Phosphinic acid derivatives of the structural formula ##STR1## or a pharmaceutically acceptable salt thereof, wherein R is H, alkyl or alkanoyloxymethylene;R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are H, alkyl, alkenyl, alkenylalkyl, aryl, arylalkyl, heteroaryl, heteroarylalkyl, hydroxyalkyl, carboxyalkyl, thioalkyl, alkoxythioalkyl, aminoalkyl, alkylaminoalkyl, cycloalkyl-substituted alkyl or heterocycloalkyl; or R.sub.1 and R.sub.2 form a cycloalkyl ring of 3-8 members and R.sub.3 and R.sub.4 are as defined; or R.sub.3 and R.sub.4 form a cycloalkyl ring of 3-7 members and R.sub.1 and R.sub.2 are as defined; or R.sub.1 and R.sub.2 together, and R.sub.3 and R.sub.4 together, each form a cycloalkyl ring;R.sub.5 is --OR.sub.9 or --NHR.sub.9, wherein R.sub.9 is hydrogen or alkyl;n is 0 or 1;A.sub.1 is p-aminobenzoyl or p-aminobenzenesulfonyl, or A.sub.1 and R.sub.5 together form a radical of an .alpha.-aminoacyl derivative; andR.sub.6 is phenylmethoxycarbonyl, arylcarbonyl, heteroarylcarbonyl or --A.sub.2 --R.sub.