Spiroacetal Moiety Research Articles

Ultraviolet-Curable Cycloaliphatic Polyesters Containing Spiroacetal Moieties for Application as Powder Coatings

Ultraviolet-Curable Cycloaliphatic Polyesters Containing Spiroacetal Moieties for Application as Powder Coatings

Transparent and toughening epoxy thermosets modified by linear telechelic polymer containing rigid spiroacetal moieties: Uncovering the relationship between the heterogeneous crosslinked network and thermoset performances

AbstractSpiroacetal moieties containing linear telechelic polymers (LTPs) with two terminal epoxy groups were facilely synthesized via the successive thiol‐ene and thiol‐epoxy click additions. The LTPs were incorporated into epoxy matrix to fabricate the transparent and toughening thermosets. In term of the miscibility of epoxy with the adduct of ethanedithiol and 3,9‐divinyl‐2,4,8,10‐tetraoxaspiro[5.5]undecane (BTU), it is proposed that the size of the formed nanostructures was small enough to allow light penetrate. Therefore, the modified thermosets were transparent, which was further confirmed by small‐angle X‐ray scattering (SAXS) measurements. The LTPs with an alternating structure of rigid spiroacetal moiety and soft thioether could formed heterogeneous crosslinked networks (HCNs) and obviously toughen epoxy thermosets. Flexural strength increased from 1.06 GPa for neat epoxy to 2.09 GPa for toughening thermosets modified with 15 wt% LTPs. The stress field intensity (KIC) value reached up to 3.93 by more than 125% compared with that of the control sample (1.75). This work uncovered the role of HCNs on performance and paved a way for technological advances toward transparent and toughening materials in epoxy thermosets.

Synthesis and properties of oligonucleotides bearing thymidine derivatives with 1,6-dioxaspiro[4.5]decane skeleton

Thymidine derivatives bearing spiroacetal moieties on the C4ʹ-position (5ʹR-spiro-thymidine and 5ʹS-spiro-thymidine) were synthesized and incorporated into oligonucleotides. The duplex- and triplex-forming abilities of both the oligonucleotides were evaluated from UV melting experiments. Oligonucleotides with the 5ʹS-spiro modifications could form thermally stable duplexes with complementary RNA and DNA; however, the 5ʹR-spiro modification significantly decreased the thermal stabilities of the duplexes and triplexes. Oligonucleotides with these spiro-thymidines showed significantly high resistance towards enzymatic degradation.

Axial chirality inversion at a spiro carbon leads to efficient synthesis of polyimine macrocycle

The synthesis and conformational preferences of a novel chiral macrocyclic polyimine possessing spiro carbon atoms is described. The key feature of the synthesis is the incorporation of an axially chiral surrounding of quaternary carbon atom having four constitutionally identical substituents into the structure of the macrocycle. This is possible by partial hydrolysis, which enables the inversion of absolute configuration, of the spiro-acetal moiety. This approach allows to obtain the macrocyclic product with almost quantitative yield. The synthesis of rhombimine with enantiopure trans -1,2-diaminocyclohexane and racemic bisaldehyde with spiro carbon atoms yields single macrocyclic product with almost quantitative yield. This is possible by partial reverse hydrolysis and thus ring opening and the inversion of absolute configuration of the a conformationally stable spiro-acetal moiety. • Diastereoselective synthesis of spiro rhombimines. • Absolute configuration of spiro moiety changes during the reaction. • New mechanism for adapting the racemic substrate in the macrocyclization reaction.

Synthesis and Properties of Poly(butylene carbonate-co-spirocyclic carbonate)

Poly(butylene carbonate)(PBC) has significantly promising applications as a degradable material in the field of polymers, while its poor thermal performance and low crystallization rate are its main defects. To overcome these shortcomings, a series of poly(butylene carbonate-co-spirocyclic carbonate)(PBSC) copolymers were synthesized from diphenyl carbonate, 1,4-butanediol and spiroglycol via two-step polycondensation reactions, using magnesium oxide as a catalyst. Differential scanning calorimetry(DSC) results indicated that the glass transition temperature(Tg) values of PBSC copolymers were enhanced from −19 °C to 56 °C with rising the spiroacetal moiety content. Thermogravimetric analysis(TGA) results showed that the resulting PBSCs have a higher thermal stability than that of poly(butylene carbonate). Wide angle X-ray diffraction(WXRD) patterns were characterized to investigate the crystallization behaviour of PBSCs. Tensile testing demonstrated that copolymerization of spiroacetal moieties into PBC chains imparted PBSC with favourable mechanical performance. Typically, PBSC30 had a tensile modulus of (1735±430) MPa, a tensile strength of (42±5) MPa and an elongation of 504%±36%.

Multifunctional hybrid 3D network based on hyaluronic acid and a copolymer containing pendant spiroacetal moieties

The elasticity, soft consistency and similarity to the human body are important characteristics of the gels. Such similarities allow the hydrogels to be biocompatible and, as a consequence, they are very attractive to be applied as biomaterials. This study presents a new strategy for developing a biohybrid complex based on a natural/synthetic polymer conjugate as gel type structure enriched with quercetin, which can be a relevant biomaterial for its antimicrobial properties. There are evidenced the preparation possibilities for the natural/synthetic structure as complex gel based on hyaluronic acid conjugated with poly(itaconic anhydride‑co‑3,9‑divinyl‑2,4,8,10‑tetraoxaspiro[5.5] undecane) copolymer decorated with quercetin. The effects of the composition on various properties were assessed. The chemical composition of bioconjugate gels was confirmed by FTIR spectroscopy. It was established that the new gel structures have enhanced swelling capacity and a typical gel-like behavior. The investigations evidenced the gels responsiveness to stimuli and their high elasticity. The new structures were tested as drug delivery systems. The in vitro release shows the dependence of the mechanism of release on the composition of the gels, evidencing a transport behavior which varies from the Fickian to super case II. In vivo investigations demonstrated a good biocompatibility after systemic administration in mice.

Functional and structural analysis of a network containing a polymer structure with spiroacetal moieties and riboflavin as low molecular mass gelator

The study presents an investigation on the conformational changes and the interaction between the components of a new network structure based on a polymer system with spiroacetal moieties, namely poly(itaconic anhydride-co-3,9-divinyl-2,4,8,10-tetraoxaspiro[5.5] undecane) (PItAU), and riboflavin (Rb) as low molecular mass gelator, in order to tailor its properties according to a targeted application. Therefore, the physicochemical characteristics of the new PItAU_Rb compound were evaluated in terms of thermal stability, microscopic, spectroscopic and dielectric properties. The maintaining of the thermal stability of the new compounds close to that of the starting copolymer was confirmed. The fluorescence emission and circular dichroism spectroscopy attested that the chemical reaction between PItAU and Rb did not destroyed the structure and the properties of Rb. Additionally, the dielectric spectroscopy investigation evidenced that the presence of Rb could lead to controlling the network architecture and the chain connectivity, which is critical for further self-aggregation organisation and network formation.

Interpenetrating polymer network systems based on poly(dimethylaminoethyl methacrylate) and a copolymer containing pendant spiroacetal moieties

The interpenetrating polymer networks (IPNs) are promising materials due to their unique properties. In this context, in the present study, new IPN structures based on poly(dimethylaminoethyl methacrylate) (PDMAEMA) and poly(itaconic anhydride-co-3,9-divinyl-2,4,8,10-tetraoxaspiro[5.5] undecane) (PITAU) were synthesized. The double network was prepared by synthesizing and crosslinking (with N, N′-methylenebis(acrylamide)) PDMAEMA in the presence of a preformed PITAU network. The effect of the two components upon some properties such us: viscoelasticity, thermal stability and swelling behavior of the new prepared gels were deeply investigated. The viscoelastic parameters indicated stronger networks for PDMAEMA/PITAU hydrogels as compared with PDMAEMA.The thermal parameters also indicate that the IPNs are more stable than PDMAEMA. The IPNs present an increased sensitivity to temperature and pH, the equilibrium swelling degree being strongly influenced by them. This behaviour highlights the possibility of controlling the release of therapeutic agents by swelling and deswelling cycles of the IPNs at different pH and temperatures, depending on composition and the application envisaged.

Using Riboflavin as Low Molecular Mass Gelator for the Preparation of a New Network Structure Having Spiroacetal Moieties

Abstract: The present investigation presents the synthesis and properties of a new nanogel structure based on poly(itaconic anhydride-co-3,9-divinyl-2,4,8,10-tetraoxaspiro[5.5] undecane) and a low molecular mass gelator, namely riboflavin. The chemical structure of the new network system was confirmed by FTIR and 1 H-NMR. The sensitivity of the new structures was evaluated by determining the hydrodynamic radius in interdependence with environmental conditions. The investigation was realized as nanogels are considered very attractive carrier systems owing to their nanometer-sized dimensions, which allow for holding large amounts of solvent and incorporating specific compounds in their nanoscale three-dimensional polymer networks.

Polyamides based on a partially bio-based spirodiamine

In this study novel, fully and partially bio-based polyamides containing spiroacetal moieties in the backbone derived from bio-glycerol and bio-ethanol were prepared and characterized. The renewable diamine employed to obtain a series of polyamides was synthesized by means of thiol-ene click chemistry and therefore contains flexible thioether as well as rigid spiroacetal moieties. Two different chemical pathways for the polymerization were investigated and evaluated. The polymerization of polyamide salts proved to be the most promising method and therefore salt polymerization was applied in the synthesis of polyamides with aliphatic and aromatic dicarboxylic acids. Subsequently, the structure of the polymers was confirmed by Maldi-ToF analysis and additionally thermal and mechanical properties were investigated revealing Tg’s between 24 and 80°C and ductile materials with moduli between 1.0 and 1.5GPa. Both semicrystalline and amorphous polyamides were thermally stable and therefore suitable for thermal processing. In the end, degradation studies were performed on the acetal containing polyamides which showed that the polymers were stable at pH 3 and higher.

Investigation on thermal, rheological, dielectric and spectroscopic properties of a polymer containing pendant spiroacetal moieties

The synthesis of “smart” molecules is in current areas of research as their specific functions can significantly improve the performance in various applications. This study is devoted to the investigation of poly(N,N dimethylacrylamide-co-3, 9-divinyl-2, 4, 8, 10-tetraoxaspiro (5.5) undecane) as “smart” macromolecular compound in order to evaluate the physico-chemical characteristics in terms of molecular weight, temperature-sensitive abilities, thermal stability, as well as its rheological, dielectric and spectroscopic properties. Differential scanning calorimetry investigation on the studied copolymer indicated a single glass transition temperature, while the rheological studies (rotational tests) confirmed a non-Newtonian shear-thinning fluid behavior of the copolymer solution. Dielectric properties of the copolymer have been evaluated in order to investigate the relaxation processes. It was found that the main contribution to dielectric relaxation derived from the non-cooperative motion of the side groups. The thermosensitive character was evidenced by the modification of the hydrodynamic radius of the macromolecular chains particles, which were estimated by dynamic light scattering technique. The fluorescence spectroscopy confirmed the structure of the copolymer, the spiroacetal moiety getting an axial conformation which is more stable, has lower energy and is more capable of making specific interactions with solvents, phenomena underlined by different shapes of the emission spectra of the copolymer.

Evaluation of the controlled release ability from the poly(2-hydroxyethyl methacrylate-co-3,9-divinyl-2,4,8,10-tetraoxaspiro[5.5]-undecane) polymer network synthesized in the presence of β-cyclodextrin

The study presents the possibility to use the 2-hydroxyethyl methacrylate--HEMA copolymer with a comonomer with spiroacetal moiety, 3,9-divinyl-2,4,8,10-tetraoxaspiro[5.5]-undecane)-U, as polymer network for loading the indomethacin--INN as drug model, and also, the controlled release evaluation of the prepared bioactive system. The macromolecular compounds were prepared by radical dispersion polymerization in the presence of a pair of surfactants. The use of cyclodextrin as surfactant allowed the building of the host-guest complexes by inclusion of hydrophobic molecules. Also, the cyclodextrin supplemented the hydrogen bonds and the hydrophobic interactions responsible for the stability of the achieved complexes. The copolymers composition and the INN inclusion onto the polymeric matrix were confirmed by FTIR analysis. The porous structure of the lyophilized P(HEMA-U) samples was illustrated by SEM images. The swelling studies evidenced the interdependence between P(HEMA-U) network properties and the spiroacetal moiety amount. Thus, the copolymers presented the increase of the equilibrium swelling degree with pH and temperature. Also, the polymeric matrices manifested dual sensitivity with pH and temperature. The in vitro release of the INN drug from the polymeric network as well as the in vivo experimental studies evidenced the benefit consequence of the spiroacetal compound presence. The clinical observation of the experimental groups does not show any behavioral modifications to suggest a possible toxic effect of these polymeric formulations with and without INN.

Nano-network with dual temperature and pH responsiveness based on copolymers of 2-hydroxyethyl methacrylate with 3,9-divinyl-2,4,8,10-tetraoxaspiro[5.5]-undecane

This study refers to the synthesis of a nano-network with dual temperature and pH responsiveness based on the 2-hydroxyethyl methacrylate (HEMA) copolymers with a comonomer with spiroacetal moiety and crosslinking capacity, namely 3,9-divinyl-2,4,8,10-tetraoxaspiro[5.5]-undecane (U). The copolymers were synthesized by radical emulsion polymerization, using 4,4′-azobis(cyanopentanoic acid) as initiator, in the presence of sodium lauryl sulfate as tensioactive agent and poly(vinyl alcohol) as protective colloid. Three copolymer variants were taken into study resulted from the different ratio between the comonomers (HEMA/U), which was about 98/2, 95/5, and 90/10, respectively. The copolymers were characterized by FTIR and thermal analysis. The copolymers sensitivity was evidenced by studying the evolution of the hydrodynamic radius and zeta potential of the polymeric particles as a function of pH. Thus, the particles size increases with the comonomer amount, from 193 nm in case of the homopolymer up to 253 nm for the copolymer with maximum content of the comonomer (10%). The increase of the particle hydrodynamic radius with the growth of temperature was also put into evidence.

Copolymerization of 2‐hydroxyethyl methacrylate with a comonomer with spiroacetal moiety

AbstractThe study reports the synthesis of a copolymer based on 2‐hydroxyethyl methacrylate and 3,9‐divinyl‐2,4,8,10‐tetraoxaspiro[5.5]undecane (U) acquired through radical polymerization in the presence of 2,2′‐azobis(2‐methylpropionitrile). The attempt was to have a solid content as high as 10 wt %. The polymerization process was conducted in the presence of a classic ionic surfactant—sodium lauryl sulfate—and comparatively using two variants of protective colloid β‐cyclodextrin and poly(aspartic acid), respectively. The prepared dispersions were characterized from the viewpoint of their hydrodynamic radius, zeta potential, and conductivity evolution during syntheses. The mean particle size and size distribution and zeta potential and conductivity were also evaluated for the synthesized polymeric particles. The compositions of the polymers were confirmed by FTIR and 1H NMR spectra, and also, the thermal stability of the polymeric compounds was evaluated. SEM and AFM investigations of the polymer morphology are also presented. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Synthesis of a spiroacetal moiety of antitumor antibiotic ossamycin by anodic oxidation

Synthesis of the spiroacetal moiety (C20–C33) of the antitumor antibiotic ossamycin, is reported. Anodic oxidation of the dithioacetal effected simultaneous removal of the protecting group and acetalization to afford the corresponding 6,6-spiroacetal structure in excellent yield.

Facile synthesis of 12-carboxamido-11-spirostenes via palladium-catalyzed carbonylation reactions

12-Carboxamido- and 12-carboxyl-11-spirostenes were synthesized from the corresponding 12-iodo-11-ene derivative in palladium-catalyzed carbonylation reactions under mild reaction conditions. The synthesis of the iodo-alkene substrate is based on the transformation of the 12-keto derivative (hecogenin) to hydrazone, which was treated with iodine in the presence of a base (1,1,3,3-tetramethyl guanidine). While various 12-carboxamides were synthesized in moderate to high yields by using simple alkyl/arylamines or amino acid methylesters as N-nucleophiles, low yields can be achieved with alcohols as O-nucleophiles. The homogeneous carbonylation reactions tolerate the 3-hydroxy substituent and the spiroacetal moiety.

Macrodasine A, a Novel Macroline Derivative Incorporating Fused Spirocyclic Tetrahydrofuran Rings Containing a Spiroacetal Moiety

A novel indole alkaloid, viz., macrodasine A, incorporating fused spirocyclic tetrahydrofuran rings onto a macroline-like moiety, was obtained from a Malayan Alstonia species. The structure, which is also notable for the presence of an unprecedented spiroacetal moiety in an indole alkaloid, was established by spectroscopic analysis.

Macrodasine A, a novel macroline derivative incorporating fused spirocyclic tetrahydrofuran rings containing a spiroacetal moiety

A novel indole alkaloid, viz., macrodasine A, incorporating fused spirocyclic tetrahydrofuran rings onto a macroline-like moiety, was obtained from a Malayan Alstonia species. The structure, which is also notable for the presence of an unprecedented spiroacetal moiety in an indole alkaloid, was established by spectroscopic analysis.

Biosynthetic studies on blazeispirane and protoblazeispirane derivatives from the cultured mycelia of the fungus Agaricus blazei

The biosynthesis of blazeispirol A, an unprecedented skeleton, was investigated by feeding 13C-labeled acetates, propionate and methionine to the growing cultures of Agaricus blazei (Agaricaceae). 13C NMR spectral analysis demonstrated the mevalonate origin of the spiroacetal moiety and the dihydronaphthalene moiety. The O-methyl and 28-methyl groups of blazeispirol A were labeled by feeding l-[methyl- 13C] methionine. The biosynthetic origin of blazeispirol A derived from ergosterol was directly demonstrated by the feeding experiment using the biosynthetically produced 14C labeled ergosterol. Furthermore, the hypothetical biogenesis of the blazeispirane and protoblazeispirane derivatives is discussed.

Sub-structure syntheses and relative stereochemistry in the bistramide (bistratene) series of marine metabolites

The (6 R*,9 S*,11 S*) and (22 S*,23 R*,27 R*,31 R*) stereochemistry, respectively, of the tetrahydropyranyl and spiroacetal moieties in bistramide A ( 1 ) have been established by stereoselective syntheses and high field NMR comparisons. Routes to the γ-amino acid moiety are outlined.