Biochemical characteristics, metabolism, and antitumor activity of several acetylated hexosamines

We have synthesized several potential inhibitors and/or modifiers of the carbohydrate portion of plasma membrane glycoconjugates. These include fluorinated and actylated analogs of D-glucosamine, D-galactosamine, and D-mannosamine. These compounds have been tested to determine their effects on both[14C] glucosamine and [3H] leucine incorporation into glycoconjugate and on cell growth and viability using P-288 murine lymphoma cells maintained in tissue culture. The most cytotoxic agent tested was 2-acetamido-2-deoxy-1,3,4,6-tetra-O-acetyl-beta-D-glucopyranose or simply beta-pentaacetylglucosamine which prevented cell growth at 10(-4)-10(-3) M. beta-Pentaacetylglucosamine cytotoxicity was correlated with its high lipid solubility, having an octanol/water partition coefficient of 0.424 as compared with 0.278 for the alpha-anomer and 0.017 for N-acetylglucosamine. In vitro metabolism studies with [4C]- and/or [3H]-labeled pentaacetylglucosamine have indicated intracellular de-O-acetylation leading to the biosynthesis of UDP-N-acetylglucosamine, followed by the incorporation of this sugar into cellular glycoprotein. Concomitant with the formation of increased amounts of this nucleotide sugar, intracellular UTP and CTP pools fell to one third normal within 3 h after the administration of 1 mM pentaacetylglucosamine. At present it is unclear whether the cytotoxicity of beta-pentaacetylglucosamine or other similar agents is due to alterations in nucleotide and nucleotide-sugar pools causing a decrease in energy charge and polynucleotide biosynthesis or is due to a direct effect on membrane glycoconjugate biosynthesis.

Syntheses and ultraviolet absorption of aza-steroids

A series of aza-steroids was synthesized containing chromophoric groups, such as a, beta-unsaturated ketones and doubly unsaturated conjugated and monoconjugated heteroannular dienones with the heteroatom in the D ring at the 20 and 17a positions. The effect of an appositely placed electronegative center in these molecules upon their ultraviolet absorptions was studied. In order to obtain a basis for the observed spectral changes, the corresponding carbocyclic compounds were also synthesized. The maximum absorptions of the aza-steroids were hypsochromically shifted relative to the carbocyclic compounds in all cases (n=8). The displacement caused by the electronegative center on absorption maximum of the chromophores is, however, highly dependent on its location within the molecules.

Testosterone production by XYY subjects

A study of plasma concentration (P1T, ng/ml), metabolic clearance rate (MCRT, L/day) and blood production rate (PBT, mg/day) was done on seven XYY subjects of various ages and four pair-matched control XY subjects by a radioinfusion technique of 1,2-3H-testosterone. Although MCRT showed no significant difference between the groups, P1T and PBT were significantly lower (P less than 0.05) in XYY subjects. Therefore, increased aggressive behavior of the XYY subjects can not be attributed to increased levels or production rates of testosterone.

Pattern of fungal isolates in cases of corneal ulcer in the western periphery of Nepal

Purpose: To find out the epidemiologic features in 686 consecutive cases of fungal keratitis presenting in a tertiary eye hospital in the western region of Nepal. Materials and methods: A prospective hospital - based study was carried out on 1880 consecutive patients presenting with corneal ulcer in the outpatient department and cornea clinic of Lumbini Eye Institute, Bhairawa, Nepal. The socio-demographic data, predisposing risk factors, prior treatment modalities, laboratory results and the distribution pattern of fungus species were analyzed. Results: Diagnosis of fungus keratitis was established in 686 (36 %) out of the total study group of 1880 cases. The spectrum of fungi isolated were Fusarium species (Fusarium spp.) in 219 (31.9 %), followed by unidentified dematiaceous 151 (22 %), curvularia 122 (17.7 %) and unidentified hyaline in 111 cases (16.1 %). Men (59.3 %) were more commonly affected than women (40.6 %). The young adults age group of 31-40 years was most commonly involved (26.6 %). Corneal trauma (58 %) and topical steroids (12 %) were the most common predisposing risk factors noted. Conclusion: In contrast to the other studies done in Nepal, we found Fusarium to be the most common fungal isolate causing corneal ulcer followed by unidentified dematiaceous, unidentified hyaline and curvularia. Corneal trauma was the commonest predisposing risk factor in causing fungal keratitis. Keywords: cornea, fungal ulcer, fusarium, unidentified dematiaceous fungus DOI: http://dx.doi.org/10.3126/nepjoph.v3i2.5262 Nepal J Ophthalmol 2011; 3(2): 118-122

Concerning the mechanism of the reaction of methyllithium with methyl 2,3-anhydro-4,6-O-benzylidene-α-D-allopyranoside to form 4,6-O-benzylidene- 1,2-didehydro-1,2-dideoxy-2-methyl-D-ribo-hexopyranose

Evidence supports the view that methyllithium, which contains no iodide or bromide ions as competitors, reacts with methyl 2,3-anhydro-4,6-O-benzylidene-α-D-allopyranoside to form, first, methyl 4,6-O-benzylidene-2-deoxy-2-methyl-α-D-altropyranoside. The latter compound then reacts with excess methyllithium to form 4,6-O-benzylidene-1,2-didehydro-1,2-dideoxy-2-methyl-D-ribo-hexopyranose by loss of methyl alcohol.A synthesis of methyl 4,6-O-benzylidene-2-deoxy-2-methyl-α-D-altropyranoside is given.The reactions of excess lithium iodide, bromide, and chloride with both methyl 2,3-anhydro-4,6-O-benzylidene-α-D-allopyranoside and methyl 2,3-anhydro-4,6-O-benzylidene-α-D-mannopyranoside are described.

Reductive cleavage with metal in liquid ammonia. III. Olefin formation from the reaction of sodium metal with methyl 4,6-O-ethylidene-3-O,S-dimethyl-2-thio-α-d-altropyranoside dissolved in 1,2-dimethoxyethane

Methyl 4,6-O-ethylidene-3-O,S-dimethyl-2-thio-α-d-altropyranoside, when heated in refluxing 1,2-dimethoxyethane with an equimolar quantity of metallic sodium, gave approximately a 75% yield of a mixture of the three olefins, methyl 2,3-didehydro-3-deoxy-4,6-O-ethylidene-S-methyl-2-thio-α-d-altropyranoside (XI), l,2-didehydro-l-deoxy-4,6-O-ethylidene-3-O,S-dimethyl-2-thio-d-ribo-hexopyranose (XII), and methyl 3,4-didehydro-3-deoxy-4,6-O-ethylidene-S-methyl-2-thio-α-d-erythro(or threo)-hexopyranoside (XIII) (tentative). Only compounds XI and XII could be separated and characterized. The structural assignments were based on a comparison with authentic samples and on nuclear magnetic resonance and infrared data, as well as on a comparison with the characteristics of analogous 4,6-O-benzylidene compounds previously reported (2).

Reductive cleavage with metal in liquid ammonia. II. Olefin formation in attempts at selective cleavage of methyl S-benzyl-4,6-O-benzylidene-3-O-methyl-2-thio-α-d-altropyranoside and its S-methyl analogue by sodium metal in liquid ammonia diluted with 1,2-dimethoxyethane

When methyl S-benzyl-4,6-O-benzylidene-3-O-methyl-2-thio-α-d-altropyranoside (VI) in liquid ammonia was treated with metallic sodium, a reductive cleavage occurred to give methyl 3-O-methyl-2-thio-α-d-altropyranoside in an 85% yield. In the solvent 1,2-dimethoxy-ethane, the reaction of sodium with VI gave little, if any, reductive cleavage. Instead, a base-catalyzed elimination of methanol took place to give the two olefins methyl,S-benzyl-4,6-O-benzylidene-2,3-didehydro-3-deoxy-2-thio-α-d-erythro-hexopyranoside (IX) and S-benzyl-4,6-O-benzylidene-l,2-didehydro-1-deoxy-3-O-methyl-2-thio-d-ribo-hexopyranose (X). Under the alkaline reaction conditions, IX isomerized partly to a third olefin, methyl.S-benzyl-4,6-O-benzylidene-3,4-didehydro-3-deoxy-2-thio-α-d-erythro(threo)-hexopyranoside (XI).In the mixed solvent liquid ammonia and 1,2-dimethoxyethane, sodium reacted with VI to give a 33% yield of the 2,3-olefin IX. Other products, no doubt present, were not isolated in this experiment.Three analogous olefins were obtained from the reaction of sodium or basic reagents with methyl 4,6-O-benzylidene-3-O,S-dimethyl-2-thio-α-d-altropyranoside (VIa) in 1,2-dimethoxyethane.

THE PREPARATION OF 4,6-O-BENZYLIDENE-D-GLUCAL AND THE REACTION OF METHYLLITHIUM WITH METHYL 2,3-ANHYDRO-4,6-O-BENZYLIDENE-α-D-ALLOPYRANOSIDE

4,6-O-Benzylidene-D-glucal has been prepared by the reaction of benzaldehyde with D-glucal. The reaction of commercial methyllithium with methyl 2,3-anhydro-4,6-O-benzylidene-α-D-allopyranoside produces the C2-methylated 1,2-unsaturated compound 4,6-O-benzylidene-1,2-didehydro-1,2-dideoxy-2-methyl-D-ribo-hexopyranose. Their structures have been proven by first-order analyses of their nuclear magnetic resonance spectra.