Rapid analysis of starch, amylose and amylopectin by high-performance size-exclusion chromatography

Starch components, amylose and amylopectin, were analyzed by high-performance size-exclusion chromatography. These two-components were separated using a two-column system (E-Linear and E-1000) and dimethyl sulphoxide as the mobile phase. The void volume (V0 = 2.22 ml) was measured using tobacco mosaic virus. Column calibration was accomplished with dextrans of known average molecular weight (Mw range = 10,100-2,000,000). The elution volume of amylopectin (Ve = 2.5 ml) indicated that this starch component was fractionated on the column system despite its very large molecular size. Standard curves were prepared from various mixtures of purified corn and wheat amylose and amylopectin. From the linear relationships obtained, the percentages of both components in corn and wheat starches were determined. The method developed proved useful to monitor the purity of amylose and amylopectin preparations, and to estimate rapidly the amylose:amylopectin ratio of starch samples.     

Synthesis and structure of ferrocenylmethylphosphines, their borane adducts, and some related derivatives

Syntheses of the known ferrocenylmethylphosphines FcCH₂PH₂ (2, Fc = (η⁵-C₅H₄)Fe(η⁵-C₅H₅)), (FcCH₂)₂PH (3), and (FcCH₂)₃P (4) have been reinvestigated. The reaction of [FcCH₂NMe₃][I] with P(CH₂OH)₃, generated from [P(CH₂OH)₄][Cl] and KOH, gave a mixture of the major product (FcCH₂)P(CH₂OH)₂ (1) and over-alkylated (FcCH₂)₂P(CH₂OH) (9). Treatment of pure 9 with Na₂S₂O₅ gave the secondary phosphine 3; slow addition of Na₂S₂O₅ to 1 gave 2 in improved yield. Reaction of 1 with [FcCH₂NMe₃][I], followed by treatment with NEt₃, gave the tertiary phosphine (FcCH₂)₃P (4), along with the known phosphonium salt [(FcCH₂)₄P][I] (5), which could be prepared in higher yield by adjusting the stoichiometry. Phosphine 4 oxidized slowly in air to yield (FcCH₂)₃P(O) (12), was protonated by HBF₄(OMe₂) to give [(FcCH₂)₃PH][BF₄] (13), and reacted with Pt(COD)Cl₂ or PtCl₂ to yield a mixture of cis- and trans-Pt(P(CH₂Fc)₃)₂Cl₂ (14). Silylation of 2 with n-BuLi/Me₃SiCl gave FcCH₂P(SiMe₃)₂ (10); treatment of 1 with Me₃SiCl/Et₃N gave FcCH₂P(CH₂OSiMe₃)₂ (11). The phosphine-borane adducts FcCH₂PH₂(BH₃) (6), (FcCH₂)₂PH(BH₃) (7), (FcCH₂)₃P(BH₃) (8) and (FcCH₂)P(CH₂OSiMe₃)₂(BH₃) (15) were prepared from the corresponding phosphines and BH₃(SMe₂). The phosphines 2, 3, and 4, phosphonium salts 5 and 13, phosphine oxide 12, Pt complex trans-14, and phosphine-boranes 6, 7 and 8 were structurally characterized by X-ray crystallography. The solid cone angle of (FcCH₂)₃P, 139°, in Pt complex 14 showed that 4 was bulkier than PPh₃, but less sterically demanding than P(t-Bu)₃. The structural changes observed on quaternization of P (shorter P-C bonds and larger angles at P), along with results from NMR and IR spectroscopy and DFT calculations, were consistent with the expected rehybridization at phosphorus. Related observations for analogous methylphosphines suggest that methyl and ferrocenylmethyl phosphorus substituents have similar properties.     

Studies on amylose and its derivatives. X. Dilute solution conformation of amylose tripropionate

Some dilute solution parameters have been measured for linear amylose tripropionate samples in ethyl acetate and tetrahydrofuran. Mark-Houwink relations for the molecular weight range 10⁴ to 1.5 × 10⁵ have been established, and the exponents are 0.58 and 0.61 in ethyl acetate and tetrahydrofuran, respectively. This indicates that the coil is only slightly expanded in these solvents. A value of 6.21 was calculated for the characteristic ratio C_∞ leading to a steric parameter of σ = 2.32. The temperature dependence of the unperturbed dimensions (d In C_∞/dT) was found to negative and of the order ?4.05 × 10^?3°K^?1.     

Branching ratios of starch via proton nuclear magnetic resonance and their use in determining amylose/amylopectin content: Evidence for three types of amylopectin

The branching (α-1,4)/(α-1,6) ratio of starch from a number of sources can be quickly and accurately determined by proton nuclear magnetic resonance (NMR). This NMR ratio, with standard ratios for isolated amylose and amylopectin, can then be used to determine the amylose/amylopectin content of starches. In the course of determining the amylose/amylopectin content of various starches, it was discovered that two different types of amylopectin standards were required to obtain results comparable to those obtained from iodine-binding amylose determinations. These two types were a waxy amylopectin, with a high level of branching, and a potato amylopectin, with a lower level of branching. A third type of amylopectin, with a still lower level of branching, is apparently present in high amylose cornstarches, leading to the conclusion that starches with higher amylose contents generally contain amylopectin with a lower level of branching. The three amylopectin types are referred to as amylopectin I, II and III, with the higher numeral coinciding with higher branching (α-1,4)/(α-1,6) ratio, or less branching.     

Electrosprayed maize starch and its constituents (amylose and amylopectin) nanoparticles

Starch consists of amylose and amylopectin. Properties such as being natural and highly hygroscopic as well as biodegradability have opened a considerable range of applications for amylose, amylopectin and starch. The performance of particles is highly dependent on their size which in turn determines the specific surface area. This work studies the application of electrospraying to fabricate maize starch and its constituents: amylose and amylopectin nanoparticles. This study showed that electrospraying technique is capable of producing amylose, amylopectin and starch nanopowder with an average particle size around 100 nm. FTIR analysis showed no reaction or interaction occurring in amylose, amylopectin and starch nanoparticle compared with their natural form. Basically, lower concentration, lower viscosity and lower surface tension of the electrospraying solution as well as higher nozzle–collector distance, higher voltage and lower feed rate lead to smaller nanoparticle size. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis and structure of some thienopyrimidine derivatives

A series of substituted thieno[2,3-d]pyrimidines was synthesized starting from ethyl-2-amino-4-isopropylthiophene-3-carboxlate. Reaction of 2-hydrazino-5-isopropyl-thieno[2,3-d]pyrimidin-4(3H)-one and its 3-methyl analogue with different reagents afforded thieno[2,3-d]triazolo[4,3-a]pyrimidines and thieno[3,2-e]triazolo[4,3-a]pyrimidines, beside open chain derivatives. Correspondence: Atef A. Hamed, Department of Chemistry, Faculty of Science, Menoufia University, Shebin El Koam, Egypt.     

Two-dimensional1H and13C NMR spectroscopy and the structural aspects of amylose and amylopectin

Summary A complete assignment of the¹³C and¹H NMR signals of amylose dissolved in dimethylsulfoxide was achieved using two-dimensional H-H and C-H correlated spectroscopy and deuterium exchange. The same methods together with an INEPT experiment provided the assignments of the¹H and¹³C NMR signals of the amylose type glucan units, the branch end glucan fragments, and a few assignments of nuclei within the branching glucan units of amylopectin dissolved in dimethylsulfoxide. From these assignments and from the integration of pertinent proton signals the branching degrees of amylose and amylopectin were derived to amount to 3.9 and 8–9%.

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Zweidimensionale¹H und¹³C-NMR-Spektroskopie und die strukturellen Aspekte von Amylose und Amylopektin

Zusammenfassung Die vollständige Zuordnung der¹³C- und¹H-NMR-Signale von in Dimethylsulfoxid gelöster Amylose konnte mit Hilfe zweidimensionaler H-H- und C-H-Korrelationsspektroskopie und Deuteriumaustausch erzielt werden. Die gleichen Methoden sowie ein INEPT-Experiment ermöglichten auch die Zuordnung der¹³C- und¹H-NMR-Signale der amylosischen Glucaneinheiten, der Verzweigungsendfragmente und einzelner Kerne im Bereich der Verzweigungsstellen von in Dimethylsulfoxid gelöstem Amylopektin. Aus diesen Zuordnungen und der Integration entsprechender Protonensignale konnte ein Verzweigungsgrad von Amylose und Amylopektin von 3.9 und 8–9% abgeleitet werden.

     

Synthesis and structure of some group VII 1,2-diacyl cyclopentadiene complexes and their pyridazine derivatives

A series of 1,2-diacyl cyclopentadienyl tricarbonyl manganese and rhenium complexes, [M(CO)₃{η⁵-1,2-C₅H₃(CO-(R)₂}] (3a–c and 4a–b), were isolated utilizing a straightforward, 3-step route. The synthetic pathway began with a 1,2-diacyl cyclopentadiene (fulvene), followed by the formation of its corresponding thallium salt and transmetallation with the appropriate pentacarbonyl metal bromide. X-ray crystallographic analysis and high-accuracy mass spectrometry confirmed the structures of the both the 4-methoxyphenyl and 4-chlorophenyl diacyl rhenium complexes, [Re(CO)₃{η⁵-1,2-C₅H₃(CO-(4-OCH₃)C₆H₄)₂}] (4a) and [Re(CO)₃{η⁵-1,2-C₅H₃(CO-(4-Cl)C₆H₄)₂}] (4b). Diacyl complexes 3a–c and 4a–b were then ring-closed with hydrazine hydrate to form their corresponding pyridazine complexes, [M(CO)₃{η⁵-1,2-C₅H₃(1,4-(R)₂N₂C₂}] (5a–c and 6a–b), in good yields (60–83%). The pyridazyl ligands were found to be relatively labile, and recrystallization of the target complexes 5a–c and 6a–b afforded only the free pyridazine ligands.     

Molecular polarizability of organic compounds and their complexes: LV. Molar volume and structure of some nitrogen compounds,their structural analogues,and some sterically hindered systems in solution

The molar volumes in solutions of a wide range of aliphatic and alicyclic amines, substituted acetanilides, 9- and 9,10-substituted anthracenes, and 1- and 1,8-substituted naphthalenes were estimated and discussed. Conformations of alkyl substituents in the aliphatic amines are similar to the conformations of the respective alkanes. Conformations (chair) of the molecules of alicyclic amines and cyclohexane are almost identical. In the molecules of acetanilides, the C(O)CH₃ group is conjugated with aromatic ring and is oriented toward the latter and toward the nitrogen of the amide group in the same manner as in acetophenone. A systematic decrease in the values of the molar volume increments of the substituents R in going from substituted benzene to substituted naphthalene and anthracene was revealed, which indicates the extension of the π-systems over the C-R bond. The orientation of 1,8-substituents relative to the naphthalene ring was found to be approximately orthogonal. A possibility to simplify the methods for determining the dipole moments and Kerr constants of compounds on the basis of their additive molar volumes was demonstrated.     

Synthesis of polynitroazaalkanols and some of their derivatives

Conclusions Polynitroazaalkanols and their chloro derivatives, nitrates, and acetates have been obtained for the first time.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 445–447, February, 1970.     

Phosphorylated chloral polyacetals and some of their derivatives

Conclusions The reaction of the acid chlorides of acetic, chloroacetic and ethylcarbonic acid, and also of phosphorus pentachloride with the products obtained by the condensation of chloral with the diethyl and diisopropyl esters of the -hydroxymethyl(ethyl)phosphonic acids gave the corresponding chloral hydrate derivatives, which were characterized.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1161–1163, May, 1967.