Polyol Fragment Research Articles

Organometallic complexation phenomenon observed during the natural aging of polyester urethane in the presence of iron corrosion

Shoes with polyester urethane soles have been stored for 3 decades in a museum environment after several months of mining use. Upon observation of sole material ageing under natural conditions, the shoes were laboratory stored since 2017 in order to evidence and follow signs of polyester urethane degradation. This study aims at characterizing a complex degradation material found on several shoes of the museum’s collection. Combining chemical composition analysis (EDX), mass spectroscopy (EGA-MS, py-GCMS) and vibrational spectroscopy (Raman and IR), results evidence the presence of iron carboxylates in different coordination modes. This study highlights the formation of a hitherto unknown degradation material of polyester urethane: an organometallic complex with iron ions coordinated with carboxylic rests of polyester polyol chains. The compound arises from the interaction between iron ions from the corrosion of structural metallic elements of the sole, and the polyester polyol fragments from the hydrolysis of the polyester urethane.

ChemInform Abstract: Medium‐Ring Stereocontrol in the Temporary Silicon‐Tethered Ring‐Closing Metathesis Approach to the Synthesis of Polyketide Fragments.

The temporary silicon-tethered ring-closing metathesis of chiral non-racemic allylic and homoallylic alcohols affords unsymmetrical Z -configured trisubstituted olefins that readily undergo stereoselective hydroboration and dihydroxylation to provide a novel approach to masked polypropionate and polyol fragments present in an array of biologically important natural products. For example, this strategy provides a convenient method for the construction of polyol fragments relevant to the secondary metabolites amphidinol 3 and lophodiol A, which have antifungal and cytotoxic activity, respectively.

Synthesis of the Acyclic Carbon Skeleton of Filipin III.

The synthesis of the carbon skeleton of filipin III, a polyenic macrolactone possessing 11 stereogenic centers, was achieved using a convergent strategy with the longest linear sequence of 19 steps starting from hexanal. Construction of the polyene was realized using two successive Heck couplings as the key steps. Control of the stereogenic centers of the polyol fragment was performed by utilizing an Evans aldolization, a 1,3-syn aldolization, enantio- and diastereoselective allylations, a hemiacetalization/oxa-Michael sequence, and a 1,3-syn reduction. The polyol and polyenic fragments were coupled using a 1,5-anti diastereoselective aldolization followed by a 1,3-anti reduction.

Medium-Ring Stereocontrol in the Temporary Silicon-Tethered Ring-Closing Metathesis Approach to the Synthesis of Polyketide Fragments

The temporary silicon-tethered ring-closing metathesis of chiral non-racemic allylic and homoallylic alcohols affords unsymmetrical Z -configured trisubstituted olefins that readily undergo stereoselective hydroboration and dihydroxylation to provide a novel approach to masked polypropionate and polyol fragments present in an array of biologically important natural products. For example, this strategy provides a convenient method for the construction of polyol fragments relevant to the secondary metabolites amphidinol 3 and lophodiol A, which have antifungal and cytotoxic activity, respectively.

Total Synthesis of (+)-Cryptocaryol A Using a Prins Cyclization/Reductive Cleavage Sequence.

The total synthesis of (+)-cryptocaryol A was achieved in 20 steps from (R)-glycidol. The key steps were a Prins cyclization/reductive cleavage sequence to construct the C5-C11 polyol fragment, a diastereoselective aldol reaction to control the stereogenic center at C13, and a stereocontrolled reduction to introduce the stereogenic center at C15.

A modular phosphate tether-mediated divergent strategy to complex polyols.

An efficient and divergent synthesis of polyol subunits utilizing a phosphate tether-mediated, one-pot, sequential RCM/CM/reduction process is reported. A modular, 3-component coupling strategy has been developed, in which, simple “order of addition” of a pair of olefinic-alcohol components to a pseudo-C2-symmetric phosphoryl chloride, coupled with the RCM/CM/reduction protocol, yields five polyol fragments. Each of the product polyols bears a central 1,3-anti-diol subunit with differential olefinic geometries at the periphery.

Synthesis and properties of new fullerene C60 derivatives, containing acetonide and polyol fragments

New mono- and hexa-methanofullerenes containing different number of acetonide groups are synthesized and characterized. Removing the acetonide protection leads to new chromatographically pure water-soluble polyol methanofullerenes with essentially quantitative yields.

A Novel Compound from the Mushroom Cryptoporus volvatus Inhibits Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) In Vitro

Porcine reproductive and respiratory syndrome (PRRS), caused by PRRS virus (PRRSV), is a serious contagious disease in the swine industry. At present, there are no effective control strategies against PRRSV. Thus, there is an urgent need for new treatment regimens that have efficacious antiviral activity to compensate for vaccines. The anti-infective effect of Cryptoporus volvatus has previously been demonstrated in Tradational Chinese Medicine. In this report, we expected to identify a new anti-PRRSV agent in the aqueous extract of C. volvatus, by employing a combination of modern chromatographic purification techniques and indirect immunofluorescence assay (IFA). Our results showed that C. volvatus extracts from every separation step differed in their inhibitory potency on PRRSV. One anti-PRRSV component designated as CM-H-L-5 was isolated from water-soluble fraction of C. volvatus. The inhibition induced by CM-H-L-5 occurred in a dose-dependent manner. CM-H-L-5 appeared to be a low-molecular-weight polyol fragment with amide groups and carboxylic acid groups. Collectively, our findings imply that CM-H-L-5 from the aqueous extract of C. volvatus has the potential to be used for anti-PRRSV therapy.

Formal synthesis of tetrahydrolipstatin and tetrahydroesterastin

A versatile and efficient approach to (3S,5R)-methyl 3-(benzyloxy)-5-(methoxymethoxy)hexadecanoate, a key chiral building block and a common polyol fragment of the anti-tumor and anti-obesity agents tetrahydrolipstatin 3 and tetrahydroesterastin 4 using both hydrolytic kinetic resolution (HKR) and proline catalyzed sequential α-aminoxylation, followed by HWE-olefination reaction is described.

Efficient and Stereoselective Access to the Polyol Fragment C9−C16 of Ansamycin Antibiotics

Efficient synthesis of the fragment C9-C16 bearing the anti,syn stereotriad of ansamycin antibiotics is described. Key steps for controlling the configuration of the three stereogenic centers involve a stereoselective Reformatsky-type reaction followed by a diastereoselective reduction of a beta-ketosulfoxide.

An asymmetric synthesis of the polyol fragment of the polyene macrolide antibiotic RK-397

A highly convergent and asymmetric synthesis of the C11–C31 polyol fragment of RK-397 as a single isomer is accomplished via a catalytic enantioselective hetero-Diels–Alder reaction and an intermolecular olefin cross-metathesis as key steps.

Divergent Synthesis of Complex Polyketide-Like Macrolides from a Simple Polyol Fragment

[structure: see text] Three stereochemically and structurally complex non-natural polyketide macrolides have been synthesized from the same simple polyol precursor. That this polyol fragment is rapidly available in quantity is key to the practicality of these syntheses and allows the targeting of more highly complex and "natural product-like" macrolides.

Absolute configuration of a polyol fragment of blasticidin A, a specific inhibitor of aflatoxin production.

Blasticidin A (1) and aflastatin A (2), Streptomyces metabolites with similar structures, are specific inhibitors of aflatoxin production by Aspergillus parasiticus. The stereochemistry of the polyol fragment of 1 (3a) containing ten chiral centers was elucidated by applying acetonide and MTPA methods to a variety of acetonide derivatives of 3a, which determined the absolute configuration of 3a. By using the similar methods, the absolute configuration of the polyol fragment of 2 (4a) was determined, which was the same as that elucidated by J-based and other chemical methods previously.

(+)-Rimocidin synthetic studies. Construction of an advanced C(1-18) polyol fragment.

[structure: see text] The synthesis of an appropriately functionalized advanced C(1-18) polyol fragment of the mycosamine-glycosylated polyene macrolide, (+)-rimocidin (1), has been achieved in a highly efficient manner. Highlights of the strategy include the S(N)2/S(N)2' addition of dithiane anions to vinyl epoxides and the multicomponent linchpin union of 2-TBS-1,3-dithiane with two advanced epoxides.

A Chiral β,δ-Dioxo-ε-sulfinyl Ester in a Convergent Enantioselective Synthesis towards the C1–C13 Polyol Fragment of Amphotericin B

This paper describes an efficient stereocontrolled and convergent approach towards the C1–C13 polyol fragment of amphotericin B. The strategy is based on the stereoselective reduction of a chiral β,γ-dioxo-ϵ-sulfinyl ester to obtain anti- or syn-1,3-diols.

Convergent synthesis of the amphotericin polyol subunit employing asymmetric dienolate addition reactions

We have described a convergent asymmetric synthesis of the polyol fragment of amphotericin B that utilizes a versatile dienolate aldol addition reaction of furfural to rapidly assemble the constituent polyol subunit. This strategy allows for the efficient synthesis of large quantities of the desired fragment while inherently flexible to allow the construction of analogs. The synthesis of the C 1C 13 fragment of amphotericin requires only eleven steps and proceeds in 28% overall yield.

Studies Towards a Total Synthesis of Amphidinolide B. Stereocontrolled Synthesis of the C14-C26 Polyol Fragment

A practical synthesis of the C14-C26 polyol unit 2 in amphidinolides B1 and B2, 1, is described which involves elaboration of the chiral unsaturated aldehyde 4 and the chiral ketone 5, followed by crossed-aldolisation of 4 and 5 in the presence of LiHMDS at -78 °C, as key steps.

Total synthesis of the polyene macrolide antibiotic roxaticin. I. Synthesis of the polyol fragment of roxaticin using a four-carbon chain extension strategy

The C11–C26 polyol fragment of roxaticin containing eight chiral centers has been prepared in a reiterative manner using coupling reactions of chiral dithianes and epoxides followed by stereoselective reduction.

Synthesis of Extended 1,3-Polyols Using Four-Carbon Units: An Approach to the Construction of the Polyol Fragment of Roxaticin

The polyol fragment of roxaticin containing eight chiral centers has been prepared in a reiterative manner using coupling reactions of chiral dithianes with epoxides followed by stereoselective reduction

Gas chromatographic analysis of cross-linked polyester-basedpolyurethane foams containing tri- and tetrafunctional alcohols after alkali fusion

An analytical procedure is described for rapid qualitative and quantitative analysis of polyester-based polyurethane foams containing tri- and tetrafunctional alcohols. The foams are conventionally the complex reaction products of an isocyanate-terminated partially cross-linked polyester prepolymer further cross-linked with water. The polymer is cleaved into the corresponding diamine, dicarboxylic acid and polyol fragments by molten alkali fusion at high temperature. These products are treated with trimethylsilylimidazole to convert polyols into volatile trimethylsilyl derivatives and hence to eliminate the extraction steps previously employed, which are of limited success with the polyfunctional alcohols. Dicarboxylic acids are converted after extraction into dimethyl ester derivatives. The polyol and acid derivatives and diamines corresponding to the diisocyanates were determined by gas chromatography.