Chemoenzymatic synthesis of a 3IV,6III-disulfated Lewis(x) pentasaccharide, a candidate ligand for human L-selectin

The disulfated pentasaccharide 3-O-SO3(-)-beta-D-Galp-(1-->4)-[alpha-L-Fucp-(1-->3)]-6-O-SO3(-)- beta-D-GlcpNAc-(1-->3)-beta-D-Galp-(1-->4)-D-Glcp was prepared according to a chemoenzymatic approach, starting from 4-methoxybenzyl O-(4-O-acetyl-2,6-di-O-benzyl-beta- D-galactopyranosyl)-(1-->4)-O-2,3,6-tri-O-benzyl-beta-D-glucopyranoside, obtained in six steps from hepta-O-acetyl lactosyl bromide. Coupling of this lactose derivative with O-(3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-beta-D-glucopyranosyl) trichloracetimidate afforded, after dephthaloylation and re-N-acetylation, 4-methoxybenzyl O-(2-acetamido-2-deoxy-beta-D- glucopyranosyl)-(1-->3)-O-(2,6-di-O-benzyl-beta-D-galactopyranosyl)-(1-- >4)- O-2,3,6-tri-O-benzyl-beta-D-glucopyranoside. Regioselective sulfation at the primary position of the glucosamine residue was then successfully achieved and the benzyl groups were removed. Enzymatic galactosylation of 4-methoxybenzyl O-(2-acetamido-2-deoxy-6-O-sulfo-beta-D- glucopyranosyl)-(1-->3)-O-beta-D-galactopyranosyl-(1-->4)-O-beta-D- glucopyranoside sodium salt, and subsequent regioselective sulfation at position 3 of the outer galactose residue through the stannylene procedure, led then to 4-methoxybenzyl O-(3-sulfo-beta-D- galactopyranosyl)-(1-->4)-O-(2-acetamido-2-deoxy-6-sulfo-beta-D- glucopyranosyl)-(1-->3)-O-beta-D-galactopyranosyl)-(1-->4)-O-beta-D- glucopyranoside disodium salt, which was finally fucosylated using human milk alpha-(1-->3/4)-fucosyltransferase affording, after anomeric deprotection, the target pentasaccharide.     

Facile synthesis of 2-methyl-[4,6-di-O-acetyl-1,2-dideoxy-3-O-(2,3,4,6-tetra-O-acetyl-D-glycopyranosyl)-alpha-D-glucopyrano-[2',1':4,5]-2-oxazolines, key intermediates for the synthesis of oligosaccharides

A simple synthesis of disaccharide oxazolines has been developed. Condensation of methyl 2-acetamido-4,6-O-benzylidene-2-deoxy-alpha-D-glucopyranoside with 2,3,4,6-tetra-O-acetyl-alpha-D-galactopyranosyl bromide, followed by removal of the 4,6-O-benzylidene group from the resulting disaccharide derivative, gave crystalline methyl 2-acetamido-2-deoxy-3-O-(2,3,4,6-tetra-O-acetyl-beta-D-galactopyranosyl)-alpha-D-glucpyranoside which, on acetolysis with acetic anhydride-acetic acid-sulfuric acid, provided 2-methyl-[4,6-di-O-acetyl-1,2-dideoxy-3-O-(2,3,4,6-tetra-O-acetyl-beta-D-galactopyranosyl)-alpha-D-glucopyrano]-[2',1':4,5]-2-oxazoline (7). Synthesis of the related alpha-D-mannopyranosyl compound was similarly accomplished. The glycosylating capability of 7 was employed for the synthesis of 6-(benzyloxycarbonylamino)hexyl-2-acetamido-4,6-di-O-acetyl-2-deoxy-3-O-(2,3,4,6-tetra-O-acetyl-beta-D-galactopyranosyl)-beta-D-glucopyranoside (18). An alternative synthesis of compound 18 is also described.     

Studies on alpha-sialylation using sialyl donors with an auxiliary 3-thiophenyl group

Reaction of the methyl ester of 2-chloro-3-S-phenyl-3-thiosialic acid (4) with sodium thiomethoxide in acetonitrile at 0 degrees C affords the methyl ester of 2-S-methyl-3-S-phenyl-2,3-di-thio-alpha-sialic acid (6a) in quantitative yield. Sialylation of tetrahydropyran-2-methanol (7) and 2-(trimethylsilyl)ethyl 2,2'3,6,6'-penta-O-benzyl-alpha-lactoside (8) with 6a in the presence of phenylsulfenyl triflate (PST) as promotor in CH3 CN at -40 degrees C gives alpha-sialosides 9 and 10 in good yield and excellent stereoselectivity. No beta-sialosides are formed in either case. Acetylation of product 10, and the subsequent reductive removal of the 3-thiophenyl group using Ph3SnH, affords 12--protected GM3 trisaccharide--in 82% yield after two steps. Sialylation of acceptor 8 with chloride 4 using silver triflate as promotor afforded 10 in 48% yield after two days at -15 degrees C in THF. A possible mechanism of sialylation with 6a that involves intermediate alpha- and beta-nitrilium ions is discussed.     

An economic synthesis of 1,2,3,4-tetra-O-acetyl-5-thio-D-xylopyranose and its transformation into 4-substituted-phenyl 1,5-dithio-D- xylopyranosides possessing antithrombotic activity

D-Xylose was converted via 1,2-O-isopropylidene-alpha-D-xylofuranose (4) into 3-O-benzoyl-5-S-benzoyl-1,2-O-isopropylidene-alpha-D-xylofuranose which, after methanolysis, acetylation and subsequent acetolysis afforded 1,2,3,4-tetra-O-acetyl-5-thio-alpha-D-xylopyranose (14) in an overall yield of 36%. Reaction of 4 with thionyl chloride gave a mixture of the diastereomeric cyclic sulfites, the structures of which were established by X-ray crystallography. Their oxidation with sodium periodate afforded the corresponding cyclic sulfate 23. Treatment of 23 with potassium thioacetate gave the potassium salt of 5-S-acetyl-1,2-O-isopropylidene-alpha-D-xylofuranose 3-O-sulfonic acid (26) which, after methanolysis, acetylation and subsequent acetolysis afforded 14 in an overall yield of 56%. Treatment of 4 with sulfuryl chloride gave a mixture containing 5-chloro-3-O-chlorosulfonyl-5-deoxy-1,2-O-isopropylidene-alpha-D- xylofuranose, 3,7,9,11-tetraoxa-4-thia-10-dimethyl-tricyclo[6,3,0, 0(2,6)]undecane S-dioxide and 23 in a 2:3:7 ratio. Tetraacetate 14 was converted into the alpha-1-bromide 18 as well as into the alpha-1-O-trichloroacetimidate 17. These three compounds were used as donors for the glycosylation with 4-cyanothiophenol, affording the 4-cyanophenyl 2,3,4-tri-O-acetyl-1,5-dithio-alpha- (29) and beta-D-xylopyranoside (30) in different ratios, depending on the reaction conditions. When donor 18 was used in the presence of potassium carbonate, besides 29 and 30 two aryl C-glycosylated-thioglycosides, i.e. 4-cyano-2-(2,3,4-tri-O-acetyl-5-thio-beta-D-xylopyranosyl)phenyl 2,3,4-tri-O-acetyl-1,5-dithio-alpha- and beta-D-xylopyranoside (32 and 33) as well as 4-cyano-2-(2,3,4-tri-O-acetyl-5-thio-beta-D-xylopyranosyl)phenyl disulfide 34 could be isolated as byproducts. Deacetylation of 30 with sodium methoxide in methanol afforded, besides 4-cyano-phenyl 1,5-dithio-beta-D-xylopyranoside (1), the corresponding 4-[(methoxy)(imino)methyl]phenyl glycoside 2. The 4-cyano group of 1 was converted into the 4-aminothiocarbonyl, the 4-(methyl-thio)(imino)methyl, the 4-amidino and the 4-(imino)(hydrazino)methyl group. All of these glycosides showed a significant antithrombotic activity on rats.     

Synthesis of the laminara-oligosaccharide methyl beta-glycosides of dp 3-8

Ethyl 2,3,4,6-tetra-O-acetyl-1-thio-alpha-D-glucopyranoside has been prepared in a good yield by anomerization of the corresponding beta-thioglucoside with tin(IV) chloride and transformed, in three steps, into ethyl 2-O-benzoyl-4,6-O-benzylidene-1-thio-alpha-D-glucopyranoside (18). Chloroacetylation of 18, followed by treatment of the product with chlorine gave crystalline 2-O-benzoyl-4,6-O-benzylidene-3-O-chloroacetyl-beta-D-glucopyranosyl chloride (20). This was coupled with methanol in the presence of silver carbonate-silver perchlorate and the product was O-dechloroacetylated to afford methyl 2-O-benzoyl-4,6-O-benzylidene-beta-D-glucopyranoside (22). Silver triflate-promoted glucosylation of 18 with 20 gave a beta-(1-->3)-linked disaccharide derivative, reaction of which with chlorine yielded crystalline O-(2-O-benzoyl-4,6-O-benzylidene-3-O-chloroacetyl-beta-D-glucopyranosyl) - (1-->3)-2-O-benzoyl-4,6-O-benzylidene-beta-D-glucopyranosyl chloride (24). Likewise, condensation of 22 with 20 gave a beta-(1-->3)-linked disaccharide glycoside, which was partially deprotected to give methyl O-(2-O-benzoyl-4,6-O-benzylidene-beta-D-glucopyranosyl)-(1-->3)-2-O-benz oyl- 4,6-O-benzylidene-beta-D-glucopyranoside (26). The methyl beta-glycosides of a homologous series of (1-->3)-linked beta-D-gluco-oligosaccharides from the tri- to the octa-saccharide have been synthesized in a blockwise manner by using 22 and 26 as the glycosyl acceptors, 24 as the disaccharide donor, and silver triflate as the promoter.     

A case of primary splenic large cell lymphoma with a t(9;14)(p13;q32)

Appropriately substituted 2,3-dihydro-7H-thiazolo[3,2-a]pyrimidin-7-ones 9-12 and 18 were considered as annulated analogues of HEPT (1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)-thymine), and some of these compounds were also found active against HIV-1, the most active one being 2,3-dihydro-5-[(3,5-dimethylphenyl)methyl]-3-ethoxy-6-ethyl-7H- thiazolo[3,2-a]pyrimidin-7-one (10b). S-Alkylation of 5-alkyl-6-(arylmethyl)-2-thiouracils 1-4 was performed with 2-bromoacetaldehyde acetals to furnish the S-[bis(alkoxy)ethyl] derivatives 5-8 and with allyl bromide to furnish S-allyl derivatives 17. The target compounds 9-12 were obtained by an N1 regioselective intramolecular cyclization reaction of silylated 5-8 using trimethylsilyl trifluoromethanesulfonate (TMS triflate) as the catalyst. Treatment of the S-allyl derivatives 17 with bromine in dry methylene chloride afforded the 3-(bromomethyl) derivatives 18.     

Behaviour of hexahydrobenzodipyrazolones towards chloroacetylation, aminoalkylation, Grignard reagent and their antimicrobial activity

Treatment of 2,3a,4,6,7a,8-hexahydrobenzo [1,2-c; 4,5-c] dipyrazole-3,7-dione (1) with chloroacetyl chloride gave the 2,6-bis (chloroacetyl) derivative (2), which on treatment with acetic anhydride pyridine afforded (3). Compound (2) when heated with pyridine afforded (1). Compound (1) underwent Mannich reaction with piperidine or morpholine and formaldehyde to give the 2,6-bis (piperidino or morpholinomethyl) derivatives (4a,b). Hydroxymethylation of (1) with formaldehyde gave the 2,6-bis (hydroxylmethyl) derivative (4), which on heating with piperidine afforded (4a), Reaction of 2,3a,4,6,7a,8-hexahydro- 2,6-bis (phenylsulphonyl) benzo [1,2-c; 4,5-?] dipyrazole-3,7-dione (7) with phenylmagnesium bromide gave dodecahydro-3,3,4a,7,7,8a-hexaphenyl-2,6- bis (phenylsulphonyl) benzo [1,2-c; 4,5-?] dipyrazole (8). Derivatives of hexahydrobenzodipyrazolone (9a-g) have been subjected to general screening for their antimicrobial activity.     

Synthesis of 4-cyanophenyl and 4-nitrophenyl 1,5-dithio-L- and -D-arabinopyranosides possessing antithrombotic activity

5-S-Benzoyl-2,3-O-isopropylidene-5-thio-L-arabinose, prepared from L-arabinose diethyl dithioacetal gave, on treatment with sodium methoxide in methanol, 4-O-benzoyl-2,3-O-isopropylidene-5-thio-L-arabinopyranose 12 which was converted into its 1-O-acetate 14. Hydrolysis of 12 in acetic acid-water afforded, after acetylation, 1,2,3-tri-O-acetyl-4-O-benzoyl-5-thio-L-arabinopyranose 17 which was transformed into 2,3-di-O-acetyl-4-O-benzoyl-5-thio-L-arabinopyranosyl bromide 20. Zemplén deacylation of 17 gave 5-thio-L-arabinopyranose which was converted via 1,2,3,4-tetra-O-acetyl-5-thio-beta-L-arabinopyranose 5 into 2,3,4-tri-O-acetyl-5-thio-beta-L-arabinopyranosyl bromide 6 and into O-(2,3,4-tri-O-acetyl-5-thio-L-arabinopyranosyl) trichloro-acetimidate 7. Glycosidation of 4-nitrophenol with 12 under the Mitsunobu conditions afforded 4-nitrophenyl 4-O-benzoyl-2,3-O-isopropylidene-5-thio-alpha- and beta-L-arabinopyranoside in a approximately 1:2 ratio. Condensation of the glycosyl donors 6, 7, 17, and 20 with 4-cyano- and 4-nitrobenzenethiol yielded, after deacylation, 4-cyano- and 4-nitrophenyl 1,5-dithio-alpha- and beta-L-arabinopyranosides 28 alpha, 28 beta, 29 alpha and 29 beta in different ratios and yields, depending on the reaction conditions applied. In a similar manner the corresponding D-isomers 30 alpha, 30 beta, 31 alpha and 31 beta were also prepared. All of these glycosides, except 28 alpha, showed a stronger oral antithrombotic effect in rats as compared to beciparcil, used as reference.     

Effects of two antihistamines on chloroquine and histamine induced weal and flare in healthy African volunteers

Reaction of the title oxazolone with N-benzyloxycarbonyl-L-aspartic acid in dichloromethane followed by addition of phenylalanine methyl ester.HCl and N-methylmorpholine gave a 90% yield of a mixture of alpha- and beta-isomers of Z-aspartylphenylalanine methyl esters in a 7:3 ratio. Reaction of the oxazolone with N-acetyl-L-aspartic acid anhydride gave a 75% yield of crystalline N-acetyl-L-aspartic acid anhydride. tert-Butoxycarbonylaspartic and Z-glutamic acids also underwent activation to give the anhydrides.     

Synthesis of oligosaccharides related to HNK-1 antigen. 2. Synthesis of 3'-O-(3-O-sulfo-beta-D-glucuronopyranosyl)-lacto-N-neotetrao se beta-propylglycoside

A derivative of allyl 3"-O-(2-acetamido-2-deoxy-beta-D-glucopyranosyl)-beta-lactoside with a free OH group at C-4GlcNAc was glycosylated with trichloroacetimidate of selectively protected GlcA(beta 1-->3)Gal alpha disaccharide in dichloromethane in the presence of trimethylsilyl triflate resulting in a pentasaccharide product with an 82% yield. This product was converted to monohydroxy derivative with a free OH group at C-3GlcA via the formation and the subsequent opening of the 6,3-lactone ring in the glucuronic acid residue. The 3"'-O-sulfation of the monohydroxy derivative, the removal of the protective groups, and the reduction of the allyl aglycon yielded the pentasaccharide propyl glycoside NaSO3-3GlcA(beta 1-->3)Gal(beta 1-->4)GlcNAc(beta 1-->3)Gal(beta 1-->4)Glc beta-Opr comprising the oligosaccharide chain of the SGGL-1 glycolipid, which is recognized by HNK-1 antibodies. NaSO3-3GlcA(beta 1--> 3)Gal beta OAll, GlcA(beta 1-->3)Gal(beta 1-->4)GlcNAc(beta 1-->3)Gal(beta 1-->4)Glc beta-OPr and GlcA(beta 1-->3)Gal beta OAll were synthesized in a similar way.     

Structure-activity relationships of N2-aryl-3-(isoxazolylsulfamoyl)-2-thiophenecarboxamides as selective endothelin receptor-A antagonists

We report here that N2-aryl-3-(isoxazolylsulfamoyl)-2-thiophenecarboxamides are potent and selective small molecule ETA receptor antagonists. The aryl group was subjected to extensive structural modification. With monosubstitution, the para position was most useful in increasing potency, with methyl being preferred. With disubstitution, 2,4-disubstitution further enhanced activity with methyl or cyano groups being preferred at the 2-position. In this series, a benzo-[d][1,3]dioxole group is equivalent to a 4-methyl group in in vitro activity and afforded the compounds with both in vivo activity and moderate half-lives.     

Synthesis of [5'-11C]ribonucleoside and -2'-deoyribonucleoside derivatives from D-ribose

An approach to the synthesis of 2'-deoxy[5'-13C]ribonucleosides was achieved by the coupling reaction of a nucleic acid base derivative with D-[5-13C]ribose derivative (8). Compound 8 was derived from D-ribose (1) by way of methyl 2,3-di-O-benzyl(Bn)-D-ribofuranoside (2), 2,3-di-O-Bn-D-ribose diethyl dithioacetal (3), 2,3-di-O-Bn-D-ribose dibenzyl acetal (4), and 4-aldehydo-2,3-di-O-Bn-D-erythrose dibenzyl acetal (5), which was then successively subjected to Wittig reaction using Ph3P13CH3I-BuLi, highly stereoselective hydroxylation with OsO4 to give 2,3-di-O-Bn-D-ribose dibenzyl acetal (7), debenzylation with H2-Pd/C. The resulting 8 was subjected to coupling reaction with a nucleic acid base to give [5'-13C]ribonucleosides. The products were derived into the corresponding 2'-deoxy[5'-13C]ribonucleoside derivatives by the established manner.     

Synthesis and biological activity of 3- and 5-amino derivatives of pyridine-2-carboxaldehyde thiosemicarbazone

A series of 3- and 5-alkylamino derivatives, as well as other structurally modified analogues of pyridine-2-carboxaldehyde thiosemicarbazone, have been synthesized and evaluated as inhibitors of CDP reductase activity and for their cytotoxicity in vitro and antineoplastic activity in vivo against the L1210 leukemia. Alkylation of 3- and 5-amino-2-(1,3-dioxolan-2-yl)pyridines (1, 2) resulted in corresponding 3-methylamino, 5-methylamino, 3-allylamino, 5-ethylamino, 5-allylamino, 5-propylamino, and 5-butylamino derivatives (5, 6, and 11-15), which were then condensed with thiosemicarbazide to yield the respective thiosemicarbazones (7, 8, and 16-20). Oxidation of 3,5-dinitro-2-methylpyridine (21) with selenium dioxide, followed by treatment with ethylene glycol and p-toluenesulfonic acid, produced the cyclic ethylene acetal, 23. Oxidation of 2-(1,3-dioxolan-2-yl)-4-methyl-5-nitropyridine (26) with selenium dioxide, followed by sequential treatment with sodium borohydride, methanesulfonyl chloride, and morpholine afforded the morpholinomethyl derivative 30. Catalytic hydrogenation of 23 and 30 with Pd/C yielded the corresponding amino derivatives 24 and 31. Catalytic hydrogenation of 5-cyano-2-methylpyridine (33) with Raney nickel, followed by treatment with acetic anhydride, gave the amide derivative 35. N-Oxidation of 35, followed by rearrangement with acetic anhydride, produced the acetate derivative, 5-[(acetylamino)methyl]-2-(acetoxymethyl)pyridine (37). Repetition of the N-oxidation and rearrangement procedures with compound 37 yielded the diacetate derivative 39. Condensation of compounds 24, 31, and 39 with thiosemicarbazide afforded the respective 3,5-diaminopyridine-, 4-(4-morpholinylmethyl)-5-aminopyridine-, and 5-(aminomethyl)pyridine-2-carboxaldehyde thiosemicarbazones (25, 32, and 40). The most biologically active compounds synthesized were the 5-(methylamino)-, 5-(ethylamino)-, and 5-(allylamino)pyridine-2-carboxaldehyde thiosemicarbazones (8, 17, and 18), which were potent inhibitors of ribonucleotide reductase activity with corresponding IC50 values of 1.3, 1.0, and 1.4 microM and which produced significant prolongation of the survival time of L1210 leukemia-bearing mice, with corresponding optimum % T/C values of 223, 204, and 215 being obtained when administered twice daily for six consecutive days at dosages of 60, 80, and 80 mg/kg, respectively.     

2-Imino-2-methoxyethyl 1-thioglycosides: new reagents for attaching sugars to proteins

Cyanomethyl 1-thioglycosides ofD-galactose, D-glucose, 2-acetamido-2-deoxy-D-glucose, and D-mannose were prepared from the respective pseudothiourea derivatives and chloroacetonitrile. The nitrile group in these cyanomethyl thioglycosides can be converted to a methyl imidate group by treatment with sodium methoxide or HC1 in dry methanol to yield 2-imino-2-methoxyethyl 1-thioglycosides (IME-thioglycosides). The factors influencing the yield of IME-thioglycosides were investigated. The most convenient method of preparing IME-thioglycosides was treating 0.1 M cyanomethyl thioglycoside peracetate in dry methanol with 0.01 M sodium methoxide at room temperature for 24-48 h (50-60% yield). These IME-thioglycosides reacted readily with simple amines, amino acids, and proteins in mildly alkaline buffer solutions. Alpha-amylase and lysozyme modified with these reagents under appropriate conditions retained full activities. Thus the IME-thioglycosides constitute a new group of reagents for attaching sugars to proteins.     

Synthesis and beta-adrenoreceptor blocking activity of [[3-(alkylamine)-2-hydroxypropyl]oximino]pyridines and O[3-(alkylamine)-2-hydroxypropyl]methylpyridine ketone oximes derivatives

[[3-(alkylamine)-2-hydroxypropyl]-2-oximino]pyridines and O-[3-(alkylamine)-2-hydroxypropyl]methylpyridine ketone oximes 5a-o were synthesized by a solid-liquid phase-transfer reaction, and their beta-adrenoreceptor blocking activity was evaluated in vitro and in vivo. The replacement of the aryl linked to the oximic carbon of the (methylenaminoxy)methyl moiety with the bioisoster pyridine ring produced a decrease of the beta-adrenergic blocking activity. The polarization of the oximic group, derived from the electron-withdrawing action of the nitrogen atom, is more evident for the 2-oxyminopyridine derivative 5d. But also conformational parameters may play an important role in the variation of activity of the compounds 5d, 5l and 5n. The replacement of the hydrogen linked to the oximic carbon with a methyl group increased the activity of the compounds 5a, 5i, 5m and 5o. The methyl could allow a delocalization of the partial positive charge present on the oximic carbon, but also its lipophilicity contributed to the increment of binding to the receptor site. None of the compounds showed high beta 1 or beta 2 selectivity in vitro. The (R) and (S) isomers of the compound 5a were synthesized and obtained with enantiomeric ratio 7:3 and 6:4, respectively. The binding tests and the pharmacological in vivo results confirmed the in vitro data.     

The subunit structure of bovine brain 14-3-2

Two aspects of the subunit structure of the bovine brain specific protein 14-3-2 have been examined. On the one hand, native 14-3-2 has been separated into two fractions by hydroxylapatite chromatography. One eluted at the same position when chromatographed on the same column, while the other redistributed into the same two fractions again. Amino acid analysis of these two forms of 14-3-2 gave results that were not significantly different under the condition of analysis. Furthermore, when each peak was subjected to cyanogen bromide cleavage, very similar elution profiles of the resultant fragments were obtained. The two pools also cross-reacted with antiserum to 14-3-2. Reaction of purified 14-3-2 with dimethylsuberimidate caused the formation of covalently bound protein units of 100,000 molecular weight when measured by sodium dodecyl sulfate polyacrylamide gel electrophoresis, as opposed to the 50,000 minimal molecular weight normally detected. On the other hand, analysis of the soluble tryptic peptides of S-[14C]carboxymethyl 14-3-2 yielded only three distinct radioactive peptides, each with one residue of S-carboxymethylcysteine whereas 8 are expected on the basis of the amino acid composition of the 50,000 molecular weight polypeptide chains. Thermolysin digestion of a similarly modified 14-3-2 preparation yielded all of the radioactivity in 5 S-carboxymethylcysteine-containing peptides. The partial amino acid sequence of these peptides indicates that they represent 4 unique areas of the polypeptide chain. Since 8 such peptides were expected, that is, double the number found, the minimum structural unit of the protein must be of 25,000 molecular weight. The results of these experiments do not permit distinction between a duplication of the structure within a single polypeptide chain or the alternate possibility of two polypeptide chains bound by unusually strong non-covalent bonds. These results suggest that 14-3-2 is a covalently linked dimer of 25,000 mol.wt. units that can aggregate to form larger species of 100,000 mol.wt. and higher.     

(Vinylaryloxy)acetic acids. A new class of diuretic agents. 3. ((2-Nitro-1-alkenyl)aryloxy)acetic acids

A series of [(2-nitro-1-alkenyl)aryloxy]acetic acids was synthesized and tested in dogs for saluretic and diuretic activity. A number of these compounds exhibit a high order of activity on iv or po administration; representative of these is (E)-[2,3-dichloro-4-(2-nitropropenyl)phenoxy]acetic acid (5). The most highly active compounds are qualitatively similar in action to [2,3-dichloro-4-(2-methylenebutyryl)phenoxylacetic acid (ethacrynic acid) in causing a prompt increase in the excretion of water and of sodium and chloride ions in approximately equimolar amounts but are three to five times as potent. Potassium ion excretion is increased but less markedly than sodium excretion.     

Stereochemistry of the in vitro and in vivo methylation of DNA by (R)- and (S)-N-[2H1,3H]methyl-N-nitrosourea and (R)- and (S)-N-nitroso-N-[2H1,3H]methyl-N-methylamine

Reaction of DNA with the carcinogens N-methyl-N-nitrosourea and N-nitroso-N,N-dimethylamine produces several methylated species including the premutagenic O6-methylguanine. The mechanism of methylation is believed to be through a methanediazonium ion. We have studied the mechanism of methylation of DNA by these carcinogens by analyzing the stereochemistry of the methyl transfer. DNA was methylated in vitro by (R)- and (S)-N-[2H1,3H]methyl-N-nitrosourea and in vivo by (R)- and (S)-N-[2H1,3H]methyl-N-methyl-N-nitrosamine and (R)- and (S)-N-[2H1,3H]methyl-N-nitrosourea. 7-Methylguanine, 3-methyladenine, O6-methylguanine, and the methylated phosphate backbone were isolated. The methyl groups were converted into acetic acid, and the stereochemistry was analyzed. The identity of the nucleophile did not influence the stereochemistry of the methylation reaction. It was found that the methyl group was transferred with an average of 73% inversion and 27% retention of configuration. The most likely mechanism for the retention of configuration is through multiple methylation events in which nucleophiles which initially react with the methanediazonium ion react as electrophiles with DNA.     

Facile method for the preparation of 7-methyl-8-oxoguanosines as an immunomodulator

Reaction of 9-(2,3,5-tri-O-acetyl-beta-D-ribofuranosyl)-7-methylguaninium iodide (2a) with hydrogen peroxide in acetic acid gave the corresponding 7-methyl-8-oxoguanosine derivative (3a) in good yield. Deprotection of 3a easily gave 7-methyl-8-oxoguanosine (1), which is well-known as an immunomodulator. Substitution of acetyl group at the N2-position of guanine ring accelerated the oxidation reaction of the 7-methylguaninium iodide.     

Studies on substances with antiblastic activity. IX. Anthramycin and analogs. IX. Synthesis of 7-methoxy-8-hydroxy-10,11-dihydro-5H-pyrrolo[2,1-c] [1,4] benzodiazepine and other compounds related to oxotomaymycin

The synthesis of some pyrrolobenzodiazepine derivatives related to oxotomaymycin, an antibiotic recovered together with tomaymycin from fermentation broths of Streptomyces achromogenes var. tomaymycetics, is described. Reaction between 2-nitro-4-benzyloxy-5-methoxybenzylbromide and pyrrole-2-carboxyaldehyde afforded 1-(2-nitro-4-benzyloxy-5-methoxybenzyl)pyrrole-2-carboxyaldehyde. Catalytic reduction of this compound with hydrogen in the presence of Pd/C gave 10,11-dihydro-8-hydroxy-7-methoxy-5H-pyrrolo[2.1-c] [1,4]benzodiazepine. Amides obtained from condensation between 2-nitro-4-benzyloxy-5-methoxybenzoic acid chloride and proline or hydroxyproline were reduced catalytically to 2,3-dihydro-8-hydroxy-7-methoxy-1H-pyrrolo [2,1-c] [1,4]benzodiazepine-5,11 (10H, 11aH)-dione and its 2-hydroxyderivative respectively. The synthesis of 10,11-dihydro-8-hydroxy-9-methoxy-5-pyrrolo [2,1-c] [1,4]benzodiazepine is also reported.