Synthesis of α- and γ-l-Glutamyl Dipeptides of l-β-Phenyl-β-Alanine

α- and γ-l-Glutamyl dipeptides of l-β-phenyl-β-alanine are synthesized for the first time from l-glutamic acid and l-β-phenyl-β-alanine. In addition, the preparations and the properties of new intermediates, that is, l-β-phenyl-β-alanine benzylester p-toluenesulfonate and the N-carbobenzyloxy-α- and γ-dipeptide benzylesters, are described. Further proof of the structure previously proposed for the naturally occurring peptide is obtained by a critical comparison of the isolated and synthetic materials by various physical and chemical methods.     

Efficient syntheses of 17-β-amino steroids

17β-Amino steroids such as 17β-amino-1,3,5(10)-estratrien-3-ol (1), 17β-amino-5α-androstan-3β-ol (2) and, 17β-amino-3β-hydroxyandrost-5-ene (3) have been widely used as a key intermediates in the synthesis of a variety of biologically active steroid derivatives though concise, high yielding syntheses of these compounds has yet to be reported. 17β-Amino-1,3,5(10)-estratrien-3-ol (1) and 17β-amino-5α-androstan-3β-ol (2) were prepared in high yield by reductive amination of estrone and epiandrosterone using benzylamine and sodium triacetoxyborohydride followed by catalytic hydrogenolysis of the resulting 17β-benzylamino derivatives. Attempts to prepare 17β-amino-3β-hydroxyandrost-5-ene (3) from dehydroepiandosterone using a similar approach resulted in partial reduction of the double bond. 17β-Amino-3β-hydroxyandrost-5-ene (3) was ultimately obtained in high yield by reductive amination of dehydroepiandosterone using allylamine and sodium triacetoxyborohydride followed by removal of the allyl group from the resulting 17β-allylamino derivative with dimethylbarbituric acid and Pd(PPh(3))(4) as catalyst.     

An acid-stable analogue of the 3-β-D-ribofuranoside of Y-base

A cyclonucleoside analogue of Y_TU riboside has been prepared and shown to be relatively stable in M-hydrochloric acid solution at room temperature.     

Synthesis of Galβ1-4GlcNAcβ- and Galβ1-3GalNAcα-O-L-serine Derivatives employing glycosidases

A new approach for the highly specific preparation of L-serine conjugates of lactosamine and Gal1-3GalNAc is described. Thus, the L-serine derivative of lactosamine Gal1-4GlcNAc-O-(N-Z)-Ser-OEt, was obtained from lactose, employing GlcNAc-O-(N-Z)-Ser-OEt as acceptor and a yeast -galactosidase as catalyst Galp 1-3GalNAc-O-(N-Alloc)-Ser-OMe was obtained from lactose, employing GalNAc-O-(N-Alloc)-Ser-OMe as acceptor and -galactosidase from bovine testes as catalyst.     

Enzymatic syntheses of GlcNAcβ1-2Man and Galβ1-4GlcNAcβ1-2Man as components of complex type sugar chains

GlcNAc1-2Man and GlcNAc1-6Man were synthesized using the reverse hydrolysis activity of -N-acetylglucosaminidase from both jack beans and Bacillus circulans. In turn, Gal1-4GlcNAc1-2Man and Gal1-4GlcNAc1-6Man were synthesized regioselectively using the transglycosylation activity of -galactosidase from Diplococcus pneumoniae and B. circulans, respectively. These di- and trisaccharides are important components of complex type sugar chains and will be used as intermediates in our synthetic studies. Abbreviations: pNp--GlcNAc, p-nitrophenyl 2-acetamido-2-deoxy--D-glucopyranoside; pNp--Gal, p-nitrophenyl -D-galacto-pyranoside     

Microbial transformations of (−)-α- and (+)-β-thujone by fungi of Absidia species

The microbial transformations of (−)-α- and (+)-β-thujone (1a and 1b) in cultures of Absidia species: Absidia coerulea AM93, Absidia glauca AM254 and Absidia cylindrospora AM336 were studied. The biotransformations of (−)-α-thujone (1a), by these fungi strains, afforded mixtures of 4-hydroxy- and 7-hydroxy-α-thujone (2 and 3). Aforementioned fungi strains were also able to hydroxylate of (+)-β-thujone at C-7 position. Only A. glauca AM254 transformed 1b to 8-hydroxy-β-thujone (7) and (2S)-2-hydroxyneoisothujol (6). The (4R)-4-hydroxyisothujole (5) was identified as one of the major metabolite of (+)-β-thujone (1b) in culture of A. cylindrospora AM336. This strain was also able to introduce hydroxy group to C-4 position in 1b without reduction of carbonyl group at C-3. The absolute configuration of all chiral centers of new (4R)-4-hydroxyisothujol (5) and (2S)-2-hydroxyneoisothujol (6) were established taking into account the configuration of (+)-β-thujone (1b) and their spectral data.     

Preparation of 9-β-D-Arabinofuranosylguanine (araG)

Abstract

A convenient practical synthesis of araG is described.     

Synthesis of 9-β-d-Glucopyranosyl-Adenine-6′-Phosphate

Synthesis of 9-β-d-glucopyranosyl-adenine-6′-phosphate is described. The method developed here involves the process of condensation of base (chloromercuri-6-benzamidopurine) (I) with phosphorylated sugar (2,3,4-tri-O-acetyl-6-diphenylphosphoryl-α-d-glucopyranosyl bromide) (II). This reaction gives crystalline 6-benzamido-9-(2′,3′,4′-tri-O-acetyl-6′-diphenylphosphoryl-β-d-glucopyranosyl)-purine (III) in high yield, which is converted to the desired nucleotide by alkaline hydrolysis.     

Synthesis and immunological evaluation of the 4-β-glucoside of HMBPP

HMBPP ((E)-4-hydroxy-3-methyl-2-butenyl pyrophosphate) is a highly potent innate immunogen that stimulates human γδ T cells expressing the Vγ2Vδ2 T cell antigen receptor. To determine if glycoside conjugates of HMBPP retain activity, the 4-β-glucoside and its acetylated homolog were synthesized and tested for their ability to stimulate γδ T cells. The glycoside HMBPP conjugate stimulated human γδ T cells with an EC(50) of 78nM. The tetraacetyl glycoside HMBPP conjugate was also active (EC(50)=360nM). The two isomeric mono-β-glucosides of the parent (E)-2-methylbut-2-ene-1,4-diol, however, were not active. Thus, HMBPP glycosylated at the 4-OH position stimulates γδ T cells as long as the pyrophosphate moiety is present.     

Syntheses of p-aminophenyl 1-thio-α- and -β-d-idopyranosides as analogs of glycosidase substrates

The p-nitrophenyl and p-aminophenyl 1-thio-α- and -β-d-idopyranosides were synthesized for use in structure-activity studies of glycosidases. Zinc chloride-catalyzed fusion of α-d-idopyranose pentaacetate with p-nitrobenzenethiol gave p-nitrophenyl 2,3,4,6-tetra-O-acetyl-1-thio-α-d-idopyranoside as an amorphous glass in 67% yield, and the crystalline β anomer in 13% yield. Deacetylation with catalytic amounts of sodium methoxide in methanol, followed by hydrogenation under pressure over palladium-on-barium sulfate catalyst, afforded p-aminophenyl 1-thio-α- and -β-d-idopyranosides.     

The Physiology and Molecular Biology of Plant 1,3-β-D-Glucanases and 1,3;1,4-β-D-Glucanases

This review covers the physiology and molecular biology of the plant β-glucanases possessing either endo-1,3-β-D-glucanase (EC 3.2.1.39) or endo-1,3;1,4-β-D-glucanase (EC 3.2.1.73) activity. These β-glucanases are structurally related enzymes that are believed to be involved in many important aspects of plant physiology and development, such as germination, growth, defense against pathogens, flowering, cellular and tissue development and differentiation, and probably other roles. They also are regulated by numerous plant hormones, biotic and abiotic elicitors and stresses, and they exhibit complex tissue- and developmental-specific gene expression.     

Histochemical demonstration of Δ 5-3β- and 17β-hydroxysteroid dehydrogenase activities in porcine ovary

Summary In histochemical investigations with the ditetrazolium salt tetranitro blue tetrazolium as final hydrogen acceptor, ⁵-3-hydroxysteroid dehydrogenase activity was found in theca interna of sexually mature and even prepuberal sows. In the granulosa cells both ⁶-3-hydroxysteroid and 17-hydroxysteroid dehydrogenase reactions were negative except in specimens from some sows in puberty or oestrus. The corpora lutea showed a positive ⁵-3-hydroxysteroid dehydrogenase activity which was somewhat more pronounced during the first week of dioestrus than in other phases of the oestrous cycle.Abbrevations NAD nicotinamide-adenine dinucleotide - NADH₂ reduced NAD - NADP nicotinamide-adenine dinucleotide phosphate - NADPH₂ reduced NADP Read at the Meeting of Umeå Medical Society in Umeå, January 25, 1966 (Bjersing, 1967).This investigation was supported by grants from the Swedish Medical Research Council (Projects No. 13X-78-01, 12X-78-02, and 12X-78-03).     

Characterization of the poly-β-1,6-N-acetylglucosamine polysaccharide component of Burkholderia biofilms

We demonstrated the production of poly-β-1,6-N-acetylglucosamine (PNAG) polysaccharide in the biofilms of Burkholderia multivorans, Burkholderia vietnamiensis, Burkholderia ambifaria, Burkholderia cepacia, and Burkholderia cenocepacia using an immunoblot assay for PNAG. These results were confirmed by further studies, which showed that the PNAG hydrolase, dispersin B, eliminated immunoreactivity of extracts from the species that were tested (B. cenocepacia and B. multivorans). Dispersin B also inhibited biofilm formation and dispersed preformed biofilms of Burkholderia species. These results imply a role for PNAG in the maintenance of Burkholderia biofilm integrity. While PNAG was present in biofilms of all of the wild-type test organisms, a ΔpgaBC mutant of B. multivorans (Mu5) produced no detectable PNAG, indicating that these genes are needed for Burkholderia PNAG formation. Furthermore, restoration of PNAG production in PNAG negative E. coli TRXWMGΔC (ΔpgaC) by complementation with B. multivorans pgaBCD confirmed the involvement of these genes in Burkholderia PNAG production. While the confocal scanning laser microscopy of untreated wild-type B. multivorans showed thick, multilayered biofilm, Mu5 and dispersin B-treated wild-type biofilms were thin, poorly developed, and disrupted, confirming the involvement of PNAG in B. multivorans biofilm formation. Thus, PNAG appears to be an important component of Burkholderia biofilms, potentially contributing to its resistance to multiple antibiotics and persistence during chronic infections, including cystic fibrosis-associated infection.     

Definitive Solution Structures for the 6-Formylated Versions of 1-(βD-Ribofuranosyl)-, 1-(2′-Deoxy-β-D-Ribofuranosyl)-, and 1-β-D-Arabinofuranosyluracil,and of Thymidine

Abstract

ROESY and NOESY NMR spectroscopic analyses of the ribofuranosyl (1a), 2′-deoxyribofuranosyl (1b), and arabinofuranosyl (1c) derivatives of 6-formyluracil in (CD₃)₂SO and D₂O solutions have established that each exclusive 7,05′-cyclic hemiacetal diastereomer of 1a,b and the major 7,O2′-cyclic hemiacetal diastereomer of 1c possess the 7R configuration. In addition, (7R)-1c has been shown to be thermodynamically more stable than (7S)-1c, contrary to our previous indication. A new, higher yielding synthetic route to 1a has been developed, 1b has been obtained for the first time in crystalline form, the route to 1c has been modified to better accommodate large scale preparations, and a new, fourth member of this class, 6-formylthymidine (1d), has been synthesized and its solution structures in (CD₃)₂SO, D₂O, and CD₃OD have been determined. Antitumor and antiviral evaluations of 1a-c have revealed no significant levels of activity.     

Syntheses of p-nitrophenyl 3- and 4-thio-β-D-glycopyranosides

Thioglycosides have proved to be useful, enzymatically stable analogs of glycosides for structural and mechanistic studies and their synthesis is considerably simplified through the use of thioglycoligases. As part of an investigation into the use of thioglycosides as potential pharmacological chaperones, and as components of glycoproteins and glycolipids, the syntheses of p-nitrophenyl 3-thio-β-d-galactopyranoside, phenyl 1,4-dithio-β-d-glucopyranoside, p-nitrophenyl 4-thio-β-d-mannopyranoside and p-nitrophenyl 2-acetamido-2-deoxy-4-thio-β-d-mannopyranoside are described.     

Action of rat liver Galβ1-4GlcNAc α(2-6)-sialyltransferase on Manβ1-4GlcNAcβ-OMe,GalNAcβ1-4GlcNAcβ-OMe,Glcβ1-4GlcNAcβ-OMe and GlcNAcβ1-4GlcNAcβ-OMe as synthetic substrates

Incubation of synthetic Man\1-4GlcNAc-OMe, GalNAc1-4GlcNAc-OMe, Glc1-4GlcNAc-OMe, and GlcNAc1-4GlcNac-OMe with CMP-Neu5Ac and rat liver Gal1-4GlcNAc (2-6)-sialyltransferase resulted in the formation of Neu5Ac2-6Man1-4GlcNAc-OMe, Neu5Ac2-6GalNAc1-4GlcNAc-OMe, Neu5Ac2-6Glc1-4GlcNAc-OMe and Neu5Ac2-6GlcNAc1-4GlcNAc-OMe, respectively. Under conditions which led to quantitative conversion of Gal1-4GlcNAc-OEt into Neu5Ac2-6Gal1-4GlcNAc-OEt, the aforementioned products were obtained in yields of 4%, 48%, 16% and 8%, respectively. HPLC on Partisil 10 SAX was used to isolate the various sialyltrisaccharides, and identification was carried out using 1- and 2-dimensional 500-MHz¹H-NMR spectroscopy.Abbreviations 2D 2-dimensional - CMP cytidine 5-monophosphate - CMP-Neu5Ac cytidine 5-monophospho--N-acetylneuraminic acid - COSY correlation spectroscopy - DQF double quantum filtered - HOHAHA homonuclear Hartmann-Hahn - MLEV composite pulse devised by M. Levitt - Neu5Ac N-acetylneuraminic acid - Neu5Ac2en 2-deoxy-2,3-didehydro-N-acetylneuraminic acid     

Synergism of 1-β-d-arabinofuranosylcytosine with itself and aphidicolin

JU56 cells have been exposed to 1-β-d-arabinofuranosylcytosine (ara-C) in S phase, and again to aphidicolin (APC) or ara-C during G₂, and examined for chromosomal aberrations at c-metaphase. It was found that the two exposures acted synergistically in the production of chromosomal lesions of both the chromatid and isochromatid type. The results were interpreted as indicating that inhibition of the G₂ repair system prevented the repair of DNA single-strand regions produced by the incorporation of ara-C during semiconservative DNA synthesis.