Poly(p‐phenylene sulfide) nonisothermal cold‐crystallization

The poly(p‐phenylene sulfide) (PPS) nonisothermal cold‐crystallization behavior was investigated in a wide heating rate range. The techniques employed were the usual Differential Scanning Calorimetry (DSC), and the less conventional FT‐IR spectroscopy and Energy Dispersive X‐ray Diffraction (EDXD). The low heating rates (Φ) explored by EDXD (0.1 K min^?1) and FT‐IR (0.5–10 K min^?1) are contiguous and complementary to the DSC ones (5–30 K min^?1). The crystallization temperature changes from 95 °C at Φ = 0.05 K min^?1 to 130 °C at Φ = 30 K min^?1. In such a wide temperature range the Kissinger model failed. The model is based on an Arrhenius temperature dependence of the crystallization rate and is widely employed to evaluate the activation energy of the crystallization process. The experimental results were satisfactorily fit by replacing in the Kissinger model the Arrhenius equation with the Vogel–Fulcher–Tamann function and fixing U* = 6.28 k J mol^?1, the activation energy needed for the chains movements, according to Hoffmann. The temperature at which the polymer chains are motionless (T_∞ = 42 °C) was found by fitting the experimental data. It appears to be reasonable in the light of our previously reported isothermal crystallization results, which indicated T_∞ = 48 °C. Moreover, at the lower heating rate, mostly explored by FT‐IR, a secondary stepwise crystallization process was well evidenced. In first approximation, it contributes to about 17% of the crystallinity reached by the sample. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2725–2736, 2005     

Preferential orientation of crystallites spatially confined in lamellar microdomains of polyethylene‐block‐[atactic poly(propylene)]

Synchrotron small angle X‐ray scattering (SAXS), wide angle X‐ray scattering (WAXS), and transmission electron microscopy were carried out for an oriented polyethylene‐block‐[atactic poly(propylene)] with a molecular weight of 1.13×10⁵ and a volume fraction of polyethylene of 0.5. Isothermal crystallization at 93°C did not destroy the pre‐formed microdomain, however, with a higher crystallization temperature, the microdomain was more heavily deformed and more crystalline lamella grew. In WAXS profiles, preferential orientation of (020) reflection peak was observed, indicating that the crystalline lamella grew in parallel with the micro domain interface.     

Stille Cross‐Coupling of a Racemic Planar‐Chiral Ferrocene and Crystallographic Trace Analysis of Catalysis Intermediates and By‐products

A pressure‐controlled procedure for the S_N1 reaction of rac‐1‐[(dimethylamino)methyl]‐2‐(tributylstannyl)ferrocene ( 1 ) to rac‐1‐(phthalimidomethyl)‐2‐(tributylstannyl)ferrocene ( 2 ) was developed. Pd⁰‐Catalyzed Stille coupling of 2 with iodobenzene afforded rac‐1‐phenyl‐2‐(N‐phthalimidomethyl)ferrocene ( 5 ) in 74% yield; after trace enrichment by crystallization of the combined mother liquors, one single crystal of each, 5 , catalysis intermediate trans‐iodo(σ‐phenyl)bis(triphenylarsino)palladium(II) ( 7 ), trans‐diiodobis(triphenylarsino)palladium(II) ( 8 ), and rac‐2,2′‐bis(phthalimidomethyl)‐1,1′‐biferrocene ( 9 ) could be isolated by crystal sorting under a microscope and characterized by X‐ray crystal structure analysis. Furthermore, 5 was deprotected to amine ( 11 ), which does even survive the Birch reduction to rac‐1‐(aminomethyl)‐2‐(cyclohexa‐2,5‐dienyl)ferrocene ( 12 ).     

Long‐term X‐ray stimulated crystallization of poly(N‐methyldodecano‐12‐lactam) in blend with poly(styrene‐stat‐acrylic acid)

The effect of X‐ray irradiation on crystallization of the blend of poly(N‐methyldodecano‐12‐lactam) (PMDL) with 29.5% of statistical copolymer poly(styrene‐stat‐acrylic acid) (PSAA) was studied using DSC, WAXD, and solid‐state ¹³C NMR methods. Significant acceleration of crystallization was found in the as‐prepared X‐ray irradiated (XI), that is, WAXD‐measured, samples compared with the nonirradiated (NI) ones. In the XI blend, the incubation period was shortened and crystallization proceeded at significantly higher rate. In the asymptote, after 100–120 days, both NI and XI samples reached the same final crystallinity of about 18%. The second DSC runs indicated that the stimulating effect of X‐ray irradiation was eliminated by heating the sample during the first run. The ¹³C NMR studies have shown that PMDL chains crystallize exclusively in cis conformation on the C? N bond. Both in neat PMDL and in the blend with PSAA, the XI samples contained a significantly higher proportion of cis conformers in amorphous phase than the NI samples. It is suggested that energy absorbed by the sample during the standard WAXD measurement helps overcome the barrier of the trans/cis transition in the PMDL molecules. This opens the way to the formation of a higher number of critical equilibrium nuclei and, finally, results in accelerated crystallization of the XI samples. No irreversible changes were found in the XI samples. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 311–321, 2008     

Influence of deformation on irreversible and reversible crystallization of poly(ethylene‐co‐1‐octene)

The effect of uniaxial deformation and subsequent relaxation at ambient temperature on irreversible and reversible crystallization of homogeneous poly(ethylene‐co‐1‐octene) with 38 mol % 1‐octene melt‐crystallized at 10 K min was explored by calorimetry, X‐ray scattering, and Fourier transform infrared spectroscopy. At 298 K, the enthalpy‐based crystallinity of annealed specimens increased irreversibly by stress‐induced crystallization from initially 15% to a maximum of, at least, 19% when a permanent set of more than 200% was attained. The crystallinity increased by formation of crystals of pseudohexagonal structure at the expense of the amorphous polymer, and as a result of destruction of orthorhombic crystals. The stress‐induced increase of crystallinity was accompanied by an increase in the apparent specific heat capacity from 2.44 to about 2.59 J g^?1 K^?1, which corresponds to an increase of the total reversibility of crystallization from, at least, 0.10 to 0.17% K^?1. The specific reversibility calculated for 100% crystallinity increased from 0.67 to 0.89% K^?1 and points to a changed local equilibrium at the interface between the crystal and amorphous phases. The deformation resulted in typical changes of the phase structure and crystal morphology that involve orientation and destruction of crystals as well as the formation of fibrils. The effect of the decrease of the entropy of the strained melt on the reversibility of crystallization and melting is discussed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1223–1235, 2002     

A synchrotron radiation study of the one‐dimensional complex of sodium with (1S)‐N‐carboxylato‐1‐(9‐deazaadenin‐9‐yl)‐1,4‐dideoxy‐1,4‐imino‐d‐ribitol,a member of the 'immucillin' family

The sodium salt of [immucillin‐A–CO₂H]⁻ (Imm‐A), namely catena‐poly[[[triaquadisodium(I)](μ‐aqua)[μ‐(1S)‐N‐carboxylato‐1‐(9‐deazaadenin‐9‐yl)‐1,4‐dideoxy‐1,4‐imino‐d ‐ribitol][triaquadisodium(I)][μ‐(1S)‐N‐carboxylato‐1‐(9‐deazaadenin‐9‐yl)‐1,4‐dideoxy‐1,4‐imino‐d ‐ribitol]] tetrahydrate], {[Na₂(C₁₂H₁₃N₄O₆)₂(H₂O)₇]·4H₂O}_n, (I), forms a polymeric chain via Na⁺—O interactions involving the carboxylate and keto O atoms of two independent Imm‐A molecules. Extensive N,O—H...O hydrogen bonding utilizing all water H atoms, including four waters of crystallization, provides crystal packing. The structural definition of this novel compound was made possible through the use of synchrotron radiation utilizing a minute fragment (volume ∼2.4 × 10⁻⁵ mm⁻³) on a beamline optimized for protein data collection. A summary of intra‐ring conformations for immucillin structures indicates considerable flexibility while retaining similar intra‐ring orientations.     

Aqueous Sulfate Separation by Sequestration of [(SO4)2(H2O)4]4− Clusters within Highly Insoluble Imine‐Linked Bis‐Guanidinium Crystals

Selective crystallization of sulfate with a simple bis‐guanidinium ligand, self‐assembled in situ from terephthalaldehyde and aminoguanidinium chloride, was employed as an effective way to separate the highly hydrophilic sulfate anion from aqueous solutions. The resulting bis‐iminoguanidinium sulfate salt has exceptionally low aqueous solubility (K_sp=2.4×10^?10), comparable to that of BaSO₄. Single‐crystal X‐ray diffraction analysis showed the sulfate anions are sequestered as [(SO₄)₂(H₂O)₄]^4? clusters within the crystals. Variable‐temperature solubility measurements indicated the sulfate crystallization is slightly endothermic (ΔH_cryst=3.7 kJ mol^?1), thus entropy driven. The real‐world utility of this crystallization‐based approach for sulfate separation was demonstrated by removing up to 99 % of sulfate from seawater in a single step.     

Highly Stereocontrolled Ring‐Opening Polymerization of Racemic Alkyl β‐Malolactonates Mediated by Yttrium [Amino‐alkoxy‐bis(phenolate)] Complexes

Yttrium [amino‐alkoxy‐bis(phenolate)]amido complexes have been used for the ring‐opening polymerization (ROP) of racemic alkyl β‐malolactonates (4‐alkoxycarbonyl‐2‐oxetanones, rac‐MLA^Rs) bearing an allyl (All), benzyl (Bz) or methyl (Me) lateral ester function. The nature of the ortho‐substituent on the phenolate rings in the metal ancillary dictated the stereocontrol of the ROP, and consequently the syndiotactic enrichment of the resulting polyesters. ROP promoted by catalysts with halogen (Cl, Br)‐disubstituted ligands allowed the first reported synthesis of highly syndiotactic PMLA^Rs (P_r ≥ 0.95); conversely, catalysts bearing bulky alkyl and aryl ortho‐substituted ligands proved largely ineffective. All polymers have been characterized by ¹H and ¹³C{¹H} NMR spectroscopy, MALDI‐ToF mass spectrometry and DSC analyses. Statistical and thermal analyses enabled the rationalization of the chain‐end control mechanism. Whereas the stereocontrol of the polymerization obeyed a Markov first‐order (Mk1) model for the ROP of rac‐MLA^Bz and rac‐MLA^All, the ROP of rac‐MLA^Me led to a chain end‐control of Markov second‐order type (Mk2). DFT computations suggest that the high stereocontrol ability featured by catalysts bearing Cl‐ and Br‐substituted ligands does not likely originate from halogen bonding between the halogen substituent and the growing polyester chain.     

Facile Synthesis,Single‐Crystal Structure,and Biological Evaluation of Novel Pyrazolo[5,1‐d][1,2,5]triazepin‐4‐ones

A facile ring‐enlargement reaction of 2,6‐diphenyl‐4H‐pyrazolo[5,1‐c][1,4]oxazin‐4‐one is described, generating the pyrazolo[5,1‐d][1,2,5]triazepin‐4‐ones in good yields. Structures of the prepared compounds were determined on the basis of IR, ¹H‐ and ¹³C‐NMR, and HR‐MS data. Moreover, the molecular structure was confirmed by the X‐ray crystal‐structure analysis of one compound that was prone to crystallization. Preliminary biological evaluation showed that the compounds 2e – 2h promote the viability and inhibit the apoptosis of vascular endothelial cells at low concentration.     

Reaction of Paramagnetic Synthon,Lithiated 4,4,5,5‐Tetramethyl‐4,5‐dihydro‐1H‐imidazol‐1‐oxyl 3‐oxide,with Cyclic Aldonitrones of the Imidazole Series

It was shown that dipole‐stabilized paramagnetic carbanion lithiated 4,4,5,5‐tetramethyl‐4,5‐dihydro‐1H‐imidazol‐1‐oxyl 3‐oxide can be attached in a nucleophilic manner to either isolated or conjugated aldonitrones of the 2,5‐dihydroimidazole 3‐oxide and 2H‐imidazole 1‐oxide series to afford adducts the subsequent oxidation of which leads to polyfunctional mono‐ and diradicals. According to XRD, at least two polymorphic modifications can be formed during crystallization of the resulting paramagnetic compounds, and for each of them, geometric parameters of the molecules are similar. An EPR spectrum of the diradical in frozen toluene has a complicated lineshape, which can be fairly well reproduced by using X‐ray diffraction structural analysis and the following set of parameters: D=14.9 mT, E=1.7 mT; tensor a(¹⁴N)=[0.260 0.260 1.625] mT, two equivalent tensors for the nitronyl nitroxide moiety a(¹⁴N)=[0.198 0.198 0.700] mT, and g≈2.007. According to our DFT and ab initio calculations, the intramolecular exchange in the diradical is very weak and most likely ferromagnetic.     

Solvatochromism in Binary Solvent Mixtures by Means of a Penta‐tert‐butyl Pyridinium N‐Phenolate Betaine Dye

The solvatochromic behavior of a penta‐tert‐butyl prydinium N‐phenolate betaine dye was studied using UV‐visible spectrophotometry in several binary mixture solvents. The solvent polarity parameter, E_T (1) (kcal. mol^?1) was calculated from the position of the longest‐wavelength intramolecular charge transfer absorption band of this penta‐tert‐butyl betaine dye. For binary solvent mixtures, all plots of E_T (1) versus the mole fraction of a more polar component are nonlinear owing to preferential solvation of the probe by one component of the binary solvent mixture. In the computation of E_T (1) it was assumed that the two solvents mixed interact to form a common structure with an E_T (1) value not always intermediate between those of the two solvents mixed. The results obtained are explained by the strong synergism observed for some of the binary mixtures with strong hydrogen bond donors (HBD) solvents such as alcohols.     

Cyclodextrins in Polymer Synthesis: Enantiodiscrimination in Free‐Radical Polymerization of Cyclodextrin‐Complexed Racemic N‐Methacryloyl‐D,L‐phenylalanine Methyl Ester

The enantiodiscriminating polymerization of racemic cyclodextrin‐complexed N‐methacryloyl‐phenylalanine methyl ester is investigated. ¹H NMR spectra of the complexes with methylated β‐cyclodextrin in D₂O manifest splittings due to chiral recognition. The different stabilities of the diastereomeric complexes influence the kinetics of the homopolymerization, particularly at 0 °C. An enrichment of the residual N‐methacryloyl‐L ‐phenylalanine methyl ester of 14 % was achieved after 21 h of polymerization.     

Two‐dimensional Fourier transform infrared spectroscopy study of biosynthesized poly(hydroxybutyrate‐co‐hydroxyhexanoate) and poly(hydroxybutyrate‐ co‐hydroxyvalerate)

Generalized two‐dimensional (2D) Fourier transform infrared correlation spectroscopy was used to investigate the effect of the comonomer compositions on the crystallization behavior of two types of biosynthesized random copolymers, poly(hydroxybutyrate‐co‐hydroxyhexanoate) and poly(hydroxybutyrate‐co‐hydroxyvalerate). The carbonyl absorption band around 1730 cm^?1 was sensitive to the degree of crystallinity. 2D correlation analysis demonstrated that the 3‐hydroxyhexanoate units preferred to remain in the amorphous phase of the semicrystalline poly(hydroxybutyrate‐co‐hydroxyhexanoate) copolymer, resulting in decreases in the degree of crystallinity and the rate of the crystallization process. The poly(hydroxybutyrate‐co‐hydroxyvalerate) copolymer maintained a high degree of crystallinity when the 3‐hydroxyvalerate fraction was increased from 0 to 25 mol % because of isodimorphism. The crystalline and amorphous absorption bands for the carbonyl bond for this copolymer, therefore, changed simultaneously. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 649–656, 2002; DOI 10.1002/polb.10126     

Ultrasound Assisted Emulsification Microextraction Based on dimetyl (E)‐2‐[(Z)‐1‐acetyl)‐2‐hydroxy‐1‐propenyl]‐2‐butenedioate for Determination of Total Amount of Iron in Water and Tea Samples

An ultrasound assisted emulsification microextraction (USAEME) is successfully used for extraction and determination of trace amount of iron in water and tea samples, followed by flame atomic absorption spectroscopy (FAAS). In this approach, a new synthetic ligand dimetyl (E)‐2‐[(Z)‐1‐acetyl)‐2‐hydroxy‐1‐propenyl]‐2‐butenedioate (DAHPB) is used as chelating agent and chloroform is selected as an extraction solvent. The factors influencing the complex formation and extraction by USAEME method are optimized. These factors are extraction solvent type as well as extraction volume, time, temperature, pH, and the amount of chelating agent. Under optimum conditions, an enrichment factor of 202.9 is obtained from only 7.1 mL of aqueous phase. The calibration graph using the preconcentration system for iron is linear between 40.0 and 800.0 μg L^?1 with a detection limit of 7.4 μg L^?1. The relative standard deviation (R.S.D) for ten replicate measurements of 500.0 μg L^?1 of iron is 2.5%.     

Biodegradable poly(trimethylene carbonate‐b‐(L‐lactide‐ran‐glycolide)) terpolymers with tailored molecular structure and advanced performance

The macroinitiator of poly(1,3‐trimethylene carbonate) (PTMC) with number‐average molecular weight ( ) of 9.6 × 10³ g mol⁻¹ was synthesized by ring‐opening polymerization at 120°C. Then, the novel terpolymer P(TMC‐b‐(LLA‐ran‐GA)) consisting of PTMC homopolymer segment attached with various monomer molar ratios of L‐lactide (LLA) and glycolide (GA) random copolymerization block was prepared with about 5.0 × 10⁴ g mol⁻¹ by ring‐opening polymerization in bulk at 140°C. The tailored molecular structures of P(TMC‐b‐(LLA‐ran‐GA)) were characterized by ¹H nuclear magnetic resonance, ¹³C NMR, FTIR, and gel permeation chromatography, and chain microstructure analysis was performed in detail with ¹³C NMR spectroscopy. The effect of GA units on the thermal and crystallization behaviors, mechanical properties, as well as biodegradability of terpolymers was investigated by differential scanning calorimetry, wide‐angle X‐ray diffraction, stress‐strain measurements, and in vitro tests in comparison with corresponding poly(trimethylene carbonate‐block‐L‐lactide) copolymer P(TMC‐b‐LLA). The results show that amorphous PTMC segments have a significant effect on condensed state behavior of the terpolymers, and the incorporation of GA units strongly decreases the crystallinity and crystallization ability of LLA segment within terpolymers because of more random LLA‐GA sequence and shorter average LLA block length. Meanwhile, the toughness of materials is greatly improved, and in vitro degradation is also accelerated. Peripheral vascular stents were 3D printed for the first time and met the requirements for application. The results show totally biodegradable terpolymers with unique molecular structure, and modifiable properties are promising new biomaterials with advanced performance for biomedical application.     

Reaction of 3‐aminoquinoline‐2,4‐diones with isocyanates. Synthesis of novel 3‐(3′‐alkyl/arylureido)quinoline‐2,4‐diones and their cyclic carbinolamide isomers

3‐Alkyl/aryl‐3‐amino‐1H,3H‐quinoline‐2,4‐diones react with alkyl/aryl isocyanates to give novel 3‐alkyl/aryl‐3‐ureido‐1H,3H‐quinoline‐2,4‐diones or 3a‐alkyl/aryl‐9b‐hydroxy‐3,3a,5,9b‐tetrahydro‐1H‐imidazo[4,5‐c]quinoline‐2,4‐diones. In some cases, a mixture of both products was obtained and separated by fractional crystallization. All compounds were characterized by their ¹H, ¹³C, ir and ms data and some of them also by ¹⁵N nmr data.     

Polymer electrolyte membranes by in situ polymerization of poly(ethylene carbonate‐co‐ethylene oxide) macromonomers in blends with poly(vinylidene fluoride‐co‐hexafluoropropylene)

Salt‐containing membranes based on polymethacrylates having poly(ethylene carbonate‐co‐ethylene oxide) side chains, as well as their blends with poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF‐HFP), have been studied. Self‐supportive ion conductive membranes were prepared by casting films of methacrylate functional poly(ethylene carbonate‐co‐ethylene oxide) macromonomers containing lithium bis(trifluorosulfonyl)imide (LiTFSI) salt, followed by irradiation with UV‐light to polymerize the methacrylate units in situ. Homogenous electrolyte membranes based on the polymerized macromonomers showed a conductivity of 6.3 × 10^?6 S cm^?1 at 20 °C. The preparation of polymer blends, by the addition of PVDF‐HFP to the electrolytes, was found to greatly improve the mechanical properties. However, the addition led to an increase of the glass transition temperature (T_g) of the ion conductive phase by ～5 °C. The conductivity of the blend membranes was thus lower in relation to the corresponding homogeneous polymer electrolytes, and 2.5 × 10^?6 S cm^?1 was recorded for a membrane containing 10 wt % PVDF‐HFP at 20 °C. Increasing the salt concentration in the blend membranes was found to increase the T_g of the ion conductive component and decrease the propensity for the crystallization of the PVDF‐HFP component. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 79–90, 2007     

Copolymerization of poly(vinyl alcohol)‐graft‐poly(1,4‐dioxan‐2‐one) with designed molecular structure by a solid‐state polymerization method

Poly(vinyl alcohol)‐graft‐poly(1,4‐dioxan‐2‐one) (PVA‐g‐PPDO) with designed molecular structure was synthesized by a solid‐state polymerization. The solid‐state copolymerization was preceded by a graft copolymerization of PDO initiated with PVA as a multifunctional initiator, and Sn (Oct)₂ as a coininitiator/catalyst in a homogeneous molten state. The polymerization temperature was then decreased and the copolymerization was carried out in a solid state. The products prepared by solid‐state polymerization were characterized by ¹H NMR and DSC, and were compared with those synthesized in the homogeneous molten state. The degree of polymerization (D_p), degree of substitution (D_s), yield and the average molecular weight of the graft copolymer with different molecular structure were calculated from the ¹H NMR spectra. The results show that the crystallization process during the solid‐state polymerization may suppress the undesirable inter‐ or intramolecular side reactions, then resulting in a controlled molecular structure of PVA‐g‐PPDO. The results of DSC measurement show that the molecular structures determine the thermal behavior of the PVA‐g‐PPDO. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3083–3091, 2006     

Crystalline Structure of Mangiferin,a C‐Glycosyl‐Substituted 9H‐Xanthen‐9‐one Isolated from the Stem Bark of Mangifera indica

The crystalline structure of mangiferin (=2‐β‐D ‐glucopyranosyl‐1,3,6,7‐tetrahydroxy‐9H‐xanthen‐9‐one; 1 ), a biologically active xanthenone C‐glycoside, isolated from the stem bark of Mangifera indica (Anacardiaceae), was unambiguously determined by single‐crystal X‐ray diffraction (XRD). The crystal structure is summarized as follows: triclinic, P1, a=7.6575(5), b=11.2094(8), c=11.8749(8) Å, α=79.967(5), β=87.988(4), γ=72.164(4)°, V=955.3(1) ų, and Z=2. The structure also shows two molecules in the asymmetric unit cell and five crystallization H₂O molecules. The packing is stabilized by several intermolecular H‐bonds involving either the two symmetry‐independent mangiferin molecules 1a and 1b , or the H₂O ones.     

7‐Iodo‐5‐aza‐7‐deazaguanine: Syntheses of Anomeric D‐ and L‐Configured 2‐Deoxyribonucleosides

Iodination of N²‐isobutyryl‐5‐aza‐7‐deazaguanine ( 7 ) with N‐iodosuccinimide (NIS) gave 7‐iodo‐N²‐isobutyryl‐5‐aza‐7‐deazaguanine ( 8 ) in a regioselective reaction (Scheme 1). Nucleobase‐anion glycosylation of 8 with 2‐deoxy‐3,5‐di‐O‐toluoyl‐α‐D ‐ or α‐L ‐erythro‐pentofuranosyl chloride furnished anomeric mixtures of D ‐ and L ‐nucleosides. The anomeric D ‐nucleosides were separated by crystallization to give the α‐D ‐anomer and β‐D ‐anomer with excellent optical purity. Deprotection gave the 7‐iodo‐5‐aza‐7‐deazaguanine 2′‐deoxyribonucleosides 3 (β‐D ; ≥99% de) and 4 (α‐D ; ≥99% de). The reaction sequence performed with the D ‐series was also applied to L ‐nucleosides to furnish compounds 5 (β‐L ; ≥99% de) and 6 (α‐L ; ≥95% de).