Synthesis of N2-alkylguanosine using Mitsunobu reaction as a key step

Peracetylated guanosine was reacted with POCl3 to give an 2-acetamido-6-chloro-9H-purine derivative, which was condensed with primary or secondary alcohols to give N2-alkylated analogues. The products were treated with mercaptoethanol in the presence of sodium methoxide to afford N2-alkylguanosines.     

A new method for the synthesis of 2'-O-benzyladenosine using Mitsunobu reaction

A new method to introduce a benzyl group onto the 2'-OH of purine ribonucleoside is described. Thus, 6-chloropurine 3'-O-benzoylriboside and its 5'-O-trityl congener were condensed with benzyl alcohol using the Mitsunobu reaction to give the 2'-O-benzyl derivative. The yields were varied from 4.6 to 62.9% depending on the solvent used. The product was converted to adenosine, indicating that the stereochemistry at C-2' is retained.     

Novel synthesis of carbocyclic nucleosides from 2-azabicyclo[2.2.1]heptanes via the reductive N2-C3 cleavage reaction as a key step

Carbocyclic ribofuranosyl and arabinofuranosyl pyrimidine nucleosides were synthesized stereoselectively from 2-azabicyclo[2.2.1]hept-5-en-3-one via NaBH4 promoted C-N bond cleavage reaction as a key step.     

Improved synthesis of cord factor analogues via the Mitsunobu reaction

Treatment of trehalose with triphenylphosphine, diisopropyl azodicarboxylate and beta-O-tetrahydropyran-2-ylmycolic acid in 1:1 hexamethylphosphoric triamide/dichloromethane, followed by removal of the tetrahydropyranyl protecting group, gave cord factor (1) in good yield, under exceptionally mild conditions. Two new cord factor analogues were similarly prepared from beta-O-methylmycolic acid and from the alpha, beta-unsaturated 'anhydro' mycolic acid respectively. The procedure, employing excess trehalose, can also be used for the synthesis of trehalose monomycolates in good yield. No protection of the carbohydrate is required.     

The Amadori rearrangement as key reaction for the synthesis of neoglycoconjugates

The Amadori rearrangement was introduced as a key step for the conjugation of carbohydrate moieties with suitable amines such as aliphatic amines and amino acid derivatives. The rearrangement products were further transformed into the corresponding 1-N,2-O cyclic carbamates employing triphosgene to obtain anomerically stable glycoconjugates. The reaction conditions were probed on a model substrate, 3,5-di-O-benzyl-alpha,beta-d-glucofuranose and further applied to d-glycero-d-gulo-heptose, which gave 'd-gluco-conjugates' in the alpha-anomeric form exclusively in high isolated yields.     

Esterification of polymer-supported hydroxyl groups using the Mitsunobu reaction

Summary Resin-bound hydroxyl groups were esterified by N-protected amino acids using triphenylphosphine and diethyl azodicarboxylate (Mitsunobu reaction) in tetrahydrofuran or dimethylformamide. The typical reaction time was 1 h and the yield for different amino acids varied from 65 to 100%. No racemization was detected in model peptides.     

A new method of synthesis of alkyl beta-glycosides using sucrose as sugar donor

Cellobiose phosphorylase from Clostridium thermocellum catalyzed the beta-anomer-selective synthesis of alkyl glucosides from cellobiose. Synthesis of alkyl beta-glucoside from inexpensive sucrose using cellobiose phosphorylase and sucrose phosphorylase from Pseudomonas saccharophilia was investigated. By combined use of these two phosphorylases, alkyl beta-glucoside was anomer-selectively synthesized from sucrose and alkyl alcohol.     

A convenient synthesis of the side chain of loteprednol etabonate--an ocular soft corticosteroid from 20-oxopregnanes using metal-mediated halogenation as a key reaction

A facile synthesis of the side chain of loteprednol etabonate, namely, chloromethyl-17α-[(ethoxycarbonyl))oxy]-11β-hydro of loteprednol etabonate, viz., chloromethyl-17α-[(ethoxycarbonyl))oxy]-11xy-3-oxoandrosta-1,4-diene-17β-carboxylate - an ocular soft corticosteroid, has been described starting from a 20-oxopregnane, namely, 3β-acetoxy-pregn-5(6),16(17)-diene-20-one (16-dehydropregnenolone acetate, i.e., 16-DPA) using our recently developed metal-mediated halogenation as a key reaction.     

A new method for the synthesis of N3-alkylated analogs of 5-fluorouracil.

5-Fluorouracil (5-FU) is converted to the adducts 1a,b then subjected to Mitsunobu reaction with the secondary alcohols to give the condensates 2a,b. Hydrogenation of 2a,b with Pd/C affords N3-alkyl-5-fluorouracil 3a,b.     

A new selective ultrahistochemical method for the demonstration of calcium using N,N-naphthaloylhydroxylamine

Summary A new, simple, rapid, and highly sensitive and selective method for the ultrahistochemical detection of calcium is described. The reagent N,N-Naphthaloylhydroxylamine (1,8-C₁₀H₆CON(ONa)CO) sodium salt was employed in this study for the demonstration of calcium at the subcellular level in relaxed and contracted muscles (smooth muscle of the stomach, thoracic aorta, and myocardial muscle cells) of the rat (in vitro as well as in vivo) and in the human vascular smooth muscle of the aorta with atherosclerotic calcification.Direct evidence of the presence of calcium in the electron-dense reaction products (calcium N,N-Naphthaloylhydroxylamine) is given by X-ray microanalysis of 1,500–2,000 Å thick sections.The significance of distributional differences in the localization of calcium in subcellular structures of relaxed and contracted muscles in discussed in relation to the role of calcium in the control of the muscle activity during the contraction-relaxation cycle.     

A new method for the synthesis of a structural gene.

A novel method of synthesizing a structural gene or gene fragment, consisting of the first synthesis of a single-stranded DNA (ssDNA), has been developed. As a preliminary test of this method, four synthetic genes or gene fragments have been synthesized. The first one with 396 base pairs (b.p.) codes for the mature rbcS from wheat, the next two with 370 and 342 b.p. respectively, for two half molecules of a gene for trichosanthin and the last one with 315 b.p. for the N-terminal 1-102 residues of human prourokinase. In all these syntheses, a plus-stranded DNA of the target gene was generally assembled by a stepwise or one step T4 DNA ligase reaction of six oligonucleotides (A, *pB, *pC, *pD, *pE and *pF) of 30-71 nucleotides long in the presence of two terminal complementary oligonucleotides (Ab' and eF') and three short inter-fragment complementary oligonucleotides (bc, cd and de). After purification, the synthetic ssDNA was inserted into a cloning vector, pWR13. The resulting product was directly used to transform a host cell. The structure of the cloned synthetic gene was confirmed by DNA sequence analysis.     

New synthesis of artepillin C,a prenylated phenol,utilizing lipase-catalyzed regioselective deacetylation as the key step

We have synthesized artepillin C, a diprenylated p-hydroxycinnamate originally isolated from Brazilian propolis and exhibiting antioxidant and antitumor activities, from 2,6-diallylphenol. Replacement of the terminal vinyl with 2,2-dimethylvinyl group by olefin cross-metathesis and subsequent transformation yielded 2,6-diprenyl-1,4-hydroquinone diacetate. Candida antarctica lipase B-catalyzed deacetylation in 2-propanol regioselectively removed the less hindered acetyl group to give 2,6-diprenyl-1,4-hydroquinone 1-monoacetate. After triflation of the liberated 4-hydroxy group, a three-carbon side chain was introduced by palladium-mediated alkenylation with methyl acrylate. Final hydrolysis of the esters furnished artepillin C.     

Parapause breakage as a key step for the continuous indoor rearing of Philaenus spumarius

The development of an efficient indoor rearing protocol of Philaenus spumarius is a key step for research on the meadow spittlebug, as it could reduce researchers' dependency on the availability and collection of univoltine individuals in the field. Here, we implemented the rearing protocol previously described by inducing females' parapause breakage before mating. This new step enables the completion of the life cycle of P. spumarius (adult to adult) in 149 days, potentially providing three generations per year under laboratory conditions.     

A new selective ultrahistochemical method for the demonstration of calcium using N,N-naphthaloylhydroxylamine.

A new, simple, rapid, and highly sensitive and selective method for the ultrahistochemical detection of calcium is described. The reagent N,N-Naphthaloylhydroxylamine (1,8-C10H6CON(ONa)CO) sodium salt was employed in this study for the demonstration of calcium at the subcellular level in relaxed and contracted muscles (smooth muscle of the stomach, thoracic aorta, and myocardial muscle cells) of the rat (in vitro as well as in vivo) and in the human vascular smooth muscle of the aorta with atherosclerotic calcification. Direct evidence of the presence of calcium in the electron-dense reaction products (calcium N,N-Naphthaloylhydroxylamine) is given by X-ray microanalysis of 1,500-2,000 A thick sections. The significance of distributional differences in the localization of calcium in subcellular structures of relaxed and contracted muscles is discussed in relation to the role of calcium in the control of the muscle activity during the contraction-relaxation cycle.     

A new method for continuous recording of the transketolase reaction

This paper describes a method for assaying transketolase activity by using hydroxypyruvate as one of substrates and following its disappearance by optical density measurements in the UV region.     

A new strategy for photoelectrochemical DNA biosensor using chemiluminescence reaction as light source

Physical light source is absolutely necessary for usual photoelectrochemical measurement. In this work, chemiluminescence reaction rather than physical light source was used for the development of a novel photoelectrochemical DNA biosensor. CIPO (bis(2,4,5-trichlro-6-n-pentoxycarbonylphenyl)oxalate)-H(2)O(2)-9,10-diphenylanthrancene was selected as a CL system, which can produce appropriate exciting light and excite photoelectro active materials Ru(bpy)(2)dppz(2+) intercalated into the double-stranded DNA. Using such simple intercalation method, a detection limit of 4.5×10(-9) M target DNA was achieved without any amplification process. In addition, the selected CL system could be used to excite AuNPs-Ru(bpy)(2)dppz(2+) complex as well as CdSe QD multilayer, which indicated a good applicability for the established method.