CHEMOENZYMATIC SYNTHESIS OF BIODEGRADABLE POLY(1’-O-VINYLADIPOYL-SUCROSE)

t A novel polymer containing the sucrose group was synthesized by radical polymerization from an enzymaticallyprepared monomer, l'-O-vinyledipoyl-sucrose (VAS). Transesterification reaction of sucrose with divinyl adipate inanhydrous pyridine catalyzed by an alkaline protease from Bacillus subtilis at 60℃ for 7 days gave VAS (yield 55%) withoutany blocking/deblocking steps. The vinyl sucrose ester could be polymerized with potassium persulfate and H_2O_2 as initiatorto give poly(l'-O-vinyladipoyl-sucrose) with M_n = 33,000 and M_w = 53,200, M_w/M_n = 1.61. The polymer was biodegradable.After 6 days in aqueous buffer (pH 7), this alkaline protease could degrade poly(l'-O-vinyladipoyl-sucrose) to M_n of ca.1080, M_w/M_n = 3.30 (37℃), and M_n of ca. 5200, M_w/M_n = 2.44 (4℃). The polymer containing the sucrose branch would be afunctional material in various application fields.     

Two new sucrose esters from the rhizome of Sparganium stoloniferum Buch.-Ham.

Two new sucrose esters, β-D-(1-O-acetyl-3,6-O-trans-diferuloyl)fructofuranosyl-α-D-2′-O-acetylglucopyranoside (1) and β-D-(1-O-acetyl-3-O-cis-feruloyl-6-O-trans-feruloyl)fructofuranosyl-α-D-2′,4′,6′-O-triacetylglucopyranoside (2), together with four known sucrose esters (3–6) have been isolated from the rhizome of Sparganium stoloniferum Buch.-Ham. Their structures were elucidated by physical and chemical evidence and spectral analysis.     

Nucleotides,Part LXIII,New 2-(4-Nitrophenyl)ethyl(Npe)- and 2-(4-Nitrophenyl)ethoxycarbonyl(Npeoc)-Protected 2′-Deoxyribonucleosides and Their 3′-Phosphoramidites – Versatile Building Blocks for Oligonucleotide Synthesis

A series of new base-protected and 5′-O-(4-monomethoxytrityl)- or 5′-O-(4,4′-dimethoxytrityl)-substituted 3′-(2-cyanoethyl diisopropylphosphoramidites) and 3′-[2-(4-nitrophenyl)ethyl diisopropylphosphoramidites] 52 – 66 and 67 – 82 , respectively, are prepared as potential building blocks for oligonucleotide synthesis (see Scheme). Thus, 3′,5′-di-O-acyl- and N ²,3′-O,5′-O-triacyl-2′-deoxyguanosines can easily be converted into the corresponding O⁶-alkyl derivatives 6 , 8 , 10 , 12 , 14 , and 16 by a Mitsunobu reaction using the appropriate alcohol. Mild hydrolysis removes the acyl groups from the sugar moiety (→ 9 , 11 , 13 , 15 , and 19 (via 18 ), resp.) which can then be tritylated (→ 38 – 42 ) and phosphitylated (→ 57 – 61 ) in the usual manner. N ²-[2-(4-nitrophenyl)ethoxycarbonyl]-substituted and N ²-[2-(4-nitrophenyl)ethoxycarbonyl]-O⁶-[2-(4-nitrophenyl)ethyl]-substituted 2′-deoxyguanosines 5 and 7 , respectively, are synthesized as new starting materials for tritylation (→ 28 , 35 , and 37 ) and phosphitylation (→ 54 , 56 , 70 , and 78 ). Various O⁴-alkylthymidines (see 20 – 24 ) are also converted to their 5′-O-dimethoxytrityl derivatives (see 43 – 47) and the corresponding phosphoramidites (see 62 – 66 and 79 – 82 ).     

2′-O,5-dimethyluridine: A total synthesis and single crystal X-ray diffraction study

A new method for the synthesis of 2′-O,5-dimethyluridine ( 5 ) has provided the title compound in a higher yield. Application of a one-pot ribosylation methodology resulted in an efficient, high yield synthesis of 5-methyluridine (ribothymine, 3b ). An X-ray diffraction analysis of 5 disclosed the conformation of the sugar moiety of this nucleoside as anti, N(3′-endo), g⁺.     

Synthesis of a New Polymer Containing Uridine and Galactose as Pendent Groups

Abstract

A new styrene compound containing a derivatized undine unit, that is, 2′,3′-O-isopropylideneuridine 5′-p-styrenesulfonate (1), was synthesized and polymerized with AIBN as an initiator. Removal of protecting isopropylidene groups from the obtained polymer gave uridine-containing polystyrene. Uridine-containing polystyrene was synthesized also by the polymerization of the deprotected monomer (2), which had been prepared by removal of isopropylidene group from 1. Copolymerization of 1 with a styrene monomer having a galactosyl moiety, that is, N-p-vinylbenzyl-4-O-(β- d -galactopyranosy)- d -gluconamide¹ (3), was carried out in dimethyl sulfoxide. However, the deprotection of the obtained copolymer failed, because the lactonamide portion was severed in the process of deisopropylidenation. On the other hand, the copolymerization of 2 with 3 in dimethylformamide and in water with AIBN as an initiator gave the target copolymer which contained both uridine and galactose residues. Polymers and copolymers were characterized by ¹H NMR spectroscopy.     

Nucleosides and Nucleotides. Part 13. Synthesis and spectral properties of 1- (3′-O-Phosphoryl-2′-deoxy-β -D-ribofuranosyl)-2(1H)-pyridone-(3′-5′)-1-(2′-deoxy-β-D-ribofuranosyl)-2 (1H)-pyridone

The dinucleoside phosphate Π_dpΠ_d ( 4 ) was synthesized from the monomers 1-(5′-O-monomethoxytrityl - 2′ - deoxy - β - D - ribofuranosyl) - 2 (1 H) - pyridone ((MeOTr) Π_d, 2 ) and 1-(5′-O-phosphoryl-3′-O-acetyl-2′-deoxy-β-D -ribofuranosyl)-(1H)-pyridone (pΠ_d(Ac), 3 ). Its 6.4% hyperchromicity and an analysis of the ¹H-NMR. spectra indicate that the conformation and the base-base interactions in 4 are similar to those in natural pyrimidine dinucleoside phosphates.     

Über Pterinchemie. 85. Mitteilung. Polyacetylierte 5,6,7,8-Tetrahydro-D- und -L-neopterine. Ein besonderer Fall von N(5)-Alkylierung des 5,6,7,8-Tetrahydroneopterin-Gerüstes

Polyacetylated 5,6,7,8-Tetrahydro-D - and L -neopterins. A Special Case of N(5)-Alkylation of 5,6,7,8-Tetrahydroneopterins Improved conditions are reported for the preparation of the earlier described (6R)- and (6S)-1′-O,2′-O,3′-O,2-N,5-pentaacetyl-5,6,7,8-tetrahydro-L -neopterins, one of which could be obtained as pure crystals. Its structure, determined by X-ray-diffraction analysis, corresponds to the (6R)-enantiomer. The method has also been used to make the corresponding D -diastereoisomers. Further acetylation of (6RS)-1′-O,2′-O,3′-O,2-N-tetraacetyl-5,6,7,8-tetrahydro-D -neopterin under drastic conditions yields a mixture of several polyacetylated D -neopterin derivatives and a polyacetylated ethyl-tetrahydro-D -neopterin which was isolated in crystalline form and established by X-ray-diffraction analysis to be (6R)-1′-O,2′-O,3′-O,4-O,2-N,2-N,8-heptaacetyl-5-ethyl-5,6,7,8-tetrahydro-D -neopterin.     

Nucleosides. Part LXI. A Simple Procedure for the Monomethylation of Protected and Unprotected Ribonucleosides in the 2′-O- and 3′-O-Position Using Diazomethane and the Catalyst Stannous Chloride

Intensive studies on the diazomethane methylation of the common ribonucleosides uridine, cytidine, adenosine, and guanosine and its derivatives were performed to obtain preferentially the 2′-O-methyl isomers. Methylation of 5′-O-(monomethoxytrityl)-N²-(4-nitrophenyl)ethoxycarbonyl-O⁶-[2-(4-nitrophenyl)ethyl]-guanosine ( 1 ) with diazomethane resulted in an almost quantitative yield of the 2′- and 3′-O-methyl isomers which could be separated by simple silica-gel flash chromatography (Scheme 1). Adenosine, cytidine, and uridine were methylated with diazomethane with and without protection of the 5′ -O-position by a mono- or dimethoxytrityl group and the aglycone moiety of adenosine and cytidine by the 2-(4-nitrophenyl)ethoxycarbonyl (npeoc) group (Schemes 2–4). Attempts to increase the formation of the 2′-O-methyl isomer as much as possible were based upon various solvents, temperatures, catalysts, and concentration of the catalysts during the methylation reaction.     

Synthesis of 2′-deoxyguanosine containing a N2-polyamine

The synthesis of benzylated N²-(4,7,10,13-tetraazatridec-1-yl)-2′-deoxyguanosines 4 was accomplished by a key nucleophilic reaction of the novel unsymmetrical polyamine 2 , with 3′,5′-O-(tetraisopropyldisiloxane-1,3-diyl)-2-chloro-2′-deoxyinosine ( 1 ).     

Synthesis of New 3′-Deoxyribonucleosides Employing the Acid-Catalyzed Fusion Method

Coupling of 4,6-dichloro-1H-imidazo[4,5-c]pyridine (2,6-dichloro-3-deaza-9H-purine) ( 1 ) with 1,2-O-di-acetyl-5-O-benzoyl-3-deoxy-β-D -ribofuranose ( 2 ), employing the acid-catalyzed fusion method, is reported (Scheme 1). The condensation reaction was regioselective and gave the three N¹-glycosylation products 3 – 5 , whereas no N³-nucleosides were detected. Treatment of 3 – 5 with methanolic ammonia afforded the corresponding deprotected nucleosides 6 – 8 . Compounds 6 and 7 were assigned the structure of the β-D - and α-D -anomeric N¹-(3′-deoxyribo)nucleosides, respectively. The third derivative 8 proved to be the α-D -anomer of a 3′-deoxyarabinonucleoside deriving from epimerization at C(2) of the sugar. The 2-chloro- and N⁶-substituted derivatives 9 , 11 , and 13 of 3′-deoxy-3-deazaadenosine ( 10 ) and of its α-D -anomer 12 can be obtained from these versatile synthons (Schemes 2 and 3).     

Nucleosides. Part LI The 2-(4-nitrophenyl)ethoxycarbonyl (npeoc) and 2-(2,4-dinitrophenyl)ethoxycarbonyl (dnpeoc) groups for protection of hydroxy functions in ribonucleosides and 2′ -deoxyribonucleosides

The Common 2′ -deoxypyrimidine and -purine nucleosides, thymidine ( 4 ), O⁴-[2-(4-nitrophenyl)ethyl]-thymidine ( 17 ), 2′-deoxy-N⁴-[2-(4-nitrophenyl)ethoxycarbonyl]cytidine ( 26 ), 2′-deoxy-N⁶-[2-(4-nitrophenyl)-ethoxycarbonyl]adenosine- 39 , and 2′-deoxy-N²-[2-(4-nitrophenyl)(ethoxycarbonyl]-O⁶-[2–4-nitrophenyl)ethyl]-guanosine ( 52 ) were further protected by the 2-(4-nitrophenyl)ethoxycarbonyl (npeoc) and the 2-(2,4-dinitrophenyl)ethoxycarbonyl (dnpeoc) group at the OH functions of the sugar moiety to form new partially and fully blocked intermediates for nucleoside and nucleotide syntheses. The corresponding 5′-O-monomethoxytrityl derivatives 5 , 18 , 30 , 40 , and 56 were also used as starting material to synthesize some other intermediates which were not obtained by direct acylations. In the ribonucleoside series, the 5′ -O-monomethoxytrityl derivatives 14 , 36 , 49 , and 63 reacted with 2-(4-nitrophenyl) ethyl chloroformate ( 1 ) to the corresponding 2′,3′-bis-carbonates 15 , 37 , 50 , and 64 which were either detriylated to 16 , 38 , 51 , and 65 , respectively, or converted by 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) treatment to the 2′,3′-cyclic carbonates 66 – 69 . The newly synthesized compounds were characterized by elemental analyses and UV and ¹H-NMR spectra.     

A Facile,Controlled Synthesis of Soluble Star Polymers Containing a Sugar Residue by Ring-Opening Metathesis Polymerization (ROMP)

Summary: Precise syntheses of soluble star polymers containing a sugar residue could be attained by adopting sequential ring-opening metathesis polymerizations of norbornene, 1,4,4a,5,8,8a-hexahydro-1,4,5,8-exo-endo-dimethanonaphtalene, and then 1,2:3,4-di-O-isopropylidene-α-D-galacto-pyranos-6-O-yl 5-norbornene-2-carboxylate using Mo(CHCMe₂Ph)(N-2,6-ⁱPr₂C₆H₃)(O^tBu)₂. The resultant polymers possessed uniform molecular weight distributions, and the M_n values could be varied by the monomer/Mo molar ratios; their spherical images were observed in the TEM micrographs.     

A New Pyranocoumarin Diester from Polygala paniculata L

A new coumarin diester has been isolated from Polygala paniculata L. (Polygalaceae) by a combination of flash chromatography on silica gel and preparative reversed-phase chromatography. Its structure has been determined as 3′-O-acetyl-4′-O-benzoylkhellactone (= 9-acetoxy-9,10-dihydro-8,8-dimethyl-2-oxo-2 H,8H-benzo[1,2-b:3,4-b′]dipyranh-10-yl benzoate) by spectroscopic methods (UV, IR, ¹H-NMR, EI-and CI-MS) and by X-ray analysis.     

Click synthesis of N1-(β-D-ribofuranosyl)-C4-(coumarin-4″-yl)-1,2,3-triazoles

A series of eight N¹-(β-D-ribofuranosyl)-C⁴-(coumarin-4′′-yl)-1,2,3-triazoles have been synthesized by Cu(I)-catalyzed click reaction of 1-azido-1-deoxy-2,3,5-tri-O-benzoyl-β-D-ribofuranose with differently substituted 4-ethynylcoumarins followed by debenzoylation of the resulted N¹-(2′,3′,5′-tri-O-benzoyl-β-D-ribofuranosyl)-C⁴-(coumarin-4″-yl)-1,2,3-triazoles in 71 to 89% overall yields. The structures of all the synthesized compounds were established on the basis of their spectral data analysis that was further confirmed by X-ray data analysis of one of the model benzoylated compounds, i.e. N¹-(2′,3′,5′-tri-O-benzoyl-β-D-ribofuranosyl)-C⁴-(7″-isopropoxycoumarin-4″-yl)-1,2,3-triazole.     

Synthesis of 5-Methyluridine and Its 5′-Mercapto-, 2-Amino-, and 4′,5′-Unsaturated Analogues

The stereospecific cis-hydroxylation of 1-(2,3-dideoxy-β-D -glyceropent-2-enofuranosyl)thymine (1) into 1-β-D -ribofuranosylthymine (2) by osmium tetroxide is described. Treatment of 2′,3′-O, O-isopropylidene-5-methyl-2,5′-anhydrouridine (8) with hydrogen sulfide or methanolic ammonia afforded 5′-deoxy-2′,3′-O, O-isopropylidene-5′-mercapto-5-methyluridine (9) and 2′,3′-O, O-isopropylidene-5-methyl-isocytidine (10) , respectively. The action of ethanolic potassium hydroxide on 5′-deoxy-5′-iodo-2′,3′-O, O-isopropylidene-5-methyluridine (7) gave rise to the corresponding 1-(5-deoxy-β-D -erythropent-4-enofuranosyl)5-methyluracil (13) and 2-O-ethyl-5-methyluridine (14) . The hydrogenation of 2 and its 2′,3′-O, O-isopropylidene derivative 4 over 5% Rh/Al₂O₃ as catalyst generated diastereoisomers of the corresponding 5-methyl-5,6-dihydrouridine ( 17 and 18 ).     

Nucleosides. Part LIX. The 2-(4-nitrophenyl)ethylsulfonyl (Npes) Group: A New Type of Protection in Nucleoside Chemistry

The 2-(4-nitrophenyl)ethylsulfonyl (npes) group is developed as a new sugar OH-blocking group in the ribonucleoside series. Its cleavage can be performed in a β-eliminating process under aprotic conditions using 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as the most effective base. Since sulfonates do not show acyl migration, partial protection of 1,2-cis-diol moieties is possible leading to new types of oligonucleotide building blocks. A series of Markiewicz-protected ribonucleosides 1–10 is converted into their 2′-O-[2-(4-nitrophenyl)ethylsulfonyl] derivatives 29–38 in which the 5′-O? Si bond can be cleaved by acid hydrolysis forming 39–45 . Subsequent monomethoxytritylation leads to 46–50 , and desilylation affords the 5′-O-(monomethoxytrityl)-2′-O-[2-(4-nitrophenyl)ethylsulfonyl]ribonucleosides 51–55 . Acid treatment to remove trityl groups do also not harm the npes group (→ 56–58 ). Unambiguous syntheses of fully blocked 2′-O-[2-(4-nitrophenyl)ethylsulfonyl]ribonucleosides 96–102 are achieved from the corresponding 3′-O-(tert-butyl)dimethylsilyl derivatives. Furthermore, various base-protected 5′-O-(monomethoxytrityl)- and 5′-O-(dimethoxytrityl)ribonucleosides, i.e. 59–77 , are treated directly with 2-(4-nitrophenyl)ethylsulfonyl chloride forming in all cases a mixture of the 2′,3′-di-O- and the two possible 2′- and 3′-O-monosulfonates 107–148 which can be separated into the pure components by chromatographic methods. The npes group is more labile towards DBU cleavage than the corresponding base-protecting 2-(4-nitrophenyl)ethyl (npe) and 2-(4-nitrophenyl)ethoxycarbonyl (npeoc) groups allowing selective deblocking which is of great synthetic potential.     

Homo and heterodinuclear complexes derived from unsymmetrical macrocyclic ligands with two coordination sites: removal of a pendant arm and migration of copper ion upon cyclization

The dinucleating macrocyclic ligands (L^2a)^2? and (L^2b)^2? were prepared by [1?:?1] cyclic condensation of N,N′-dipropionitrile-N,N′-ethylene-di(5-methyl-3-formyl-2-hydroxybenzylamine or N,N′-dipropionitrile-N,N′-ethylene-di(5-bromo-3-formyl-2-hydroxybenzylamine with 1,3-diaminopropane. The ligands include dissimilar N(amine)₂O₂ and N(imine)₂O₂ coordination sites sharing two phenolic oxygen atoms and containing two propionitrile pendant arms on the amine nitrogen atoms. A series of mono- and dinuclear complexes were synthesized and characterized on the basis of elemental analysis, molar conductance measurement, X-ray crystallography, IR, NMR, and UV-Vis spectroscopies as well as cyclic voltammetric measurements. During the cyclization copper(II) migrates from the N(amine)₂O₂ to the N(imine)₂O₂ coordination site and one of the propionitrile pendant arms is removed. The heterodinuclear complexes [ZnL²Cu(OAc)]⁺ were prepared by a transmetallation reaction. The characterization results showed that the two metal ions are bridged by two phenolic oxygen atoms and an acetate group, providing distorted five-coordinate geometries for both metals.     

Oligonucleotides Containing Novel 4′‐C‐ or 3′‐C‐(Aminoalkyl)‐Branched Thymidines

The synthesis of four novel 3′‐C‐branched and 4′‐C‐branched nucleosides and their transformation into the corresponding 3′‐O‐phosphoramidite building blocks for automated oligonucleotide synthesis is reported. The 4′‐C‐branched key intermediate 11 was synthesized by a convergent strategy and converted to its 2′‐O‐methyl and 2′‐deoxy‐2′‐fluoro derivatives, leading to the preparation of novel oligonucleotide analogues containing 4′‐C‐(aminomethyl)‐2′‐O‐methyl monomer X and 4′‐C‐(aminomethyl)‐2′‐deoxy‐2′‐fluoro monomer Y (Schemes 2 and 3). In general, increased binding affinity towards complementary single‐stranded DNA and RNA was obtained with these analogues compared to the unmodified references (Table 1). The presence of monomer X or monomer Y in a 2′‐O‐methyl‐RNA oligonucleotide had a negative effect on the binding affinity of the 2′‐O‐methyl‐RNA oligonucleotide towards DNA and RNA. Starting from the 3′‐C‐allyl derivative 28 , 3′‐C‐(3‐aminopropyl)‐protected nucleosides and 3′‐O‐phosphoramidite derivatives were synthesized, leading to novel oligonucleotide analogues containing 3′‐C‐(3‐aminopropyl)thymidine monomer Z or the corresponding 3′‐C‐(3‐aminopropyl)‐2′‐O,5‐dimethyluridine monomer W (Schemes 4 and 5). Incorporation of the 2′‐deoxy monomer Z induced no significant changes in the binding affinity towards DNA but decreased binding affinity towards RNA, while the 2′‐O‐methyl monomer Z induced decreased binding affinity towards DNA as well as RNA complements (Table 2).     

Enzymatic synthesis of novel quercetin sialyllactoside derivatives

Quercetin and its derivatives are important flavonols that show diverse biological activity, such as antioxidant, anticarcinogenic, anti-inflammatory, and antiviral activities. Adding different substituents to quercetin may change the biochemical activity and bioavailability of molecules, when compared to the aglycone. Here, we have synthesised two novel derivatives of quercetin, quercetin-3-O-β-d-glucopyranosyl, 4′′-O-d-galactopyranosyl 3′′′-O-α-N-acetyl neuraminic acid i.e. 3′-sialyllactosyl quercetin (3′SL-Q) and quercetin-3-O-β-d-glucopyranosyl, 4′′-O-β-d-galactopyranosyl 6′′′-O-α-N-acetyl neuraminic acid i.e. 6′-sialyllactosyl quercetin (6′SL-Q) with the use of glycosyltransferases and sialyltransferases enzymes. These derivatives of quercetin were characterised by high-resolution quadrupole-time-of-flight electrospray ionisation mass spectrometry (HR-QTOF-ESI/MS) and ¹H and ¹³C nuclear magnetic resonance (NMR) analyses.