Conformational studies of sequential polypeptides of L-Alanine and β-Alanine

Summary In order to investigate the effect of the -alanine residue on the conformational stability of -helical poly(L-alanine), studies have been made on the conformations of sequential copolypeptides having the following repeating sequences: (L-Ala--Ala) _n , (L-Ala-L-Ala--Ala) _n , (L-Ala--Ala-L-Ala-L-Ala) _n and (L-Ala-L-Ala-X) _n , where X is D,L--amino-isobutyric acid residue. Conformations of these polypeptides were measured both in the solution and solid states by means of optical rotatory dispersion, infrared and far-infrared spectroscopies and X-ray diffractions. All the copolypeptides studied here did not give the -helix. It may be, therefore, concluded that the -alanine residue is not incorporated in but impairs the -helix of poly(L-alanine), since the hydrogen bond periodicity in the -helical chain is disturbed by the introduction of such a -amino acid as -alanine.With 5 figures and 2 tables     

Kinetics of oxidation of carbonyl compounds by peroxomonosulfate. Formaldehyde, formic acid and formate anion

Kinetics of oxidation of formaldehyde, formic acid and formate anion by peroxomonosulfate (PMS) were studied. Formaldehyde is oxidized both by HSO ₅ ^– and SO ₅ ^2– , whereas formic acid and formate ion are oxidized by SO ₅ ^2– alone. The kinetic results show that the formaldehyde is 10³ times more reactive than formic acid, which in turn reacts 10² times faster than formate anion. Mechanisms are discussed in terms of the kinetic results.

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, . HSO ₅ ^– , SO ₅ ^2– , SO ₅ ^2– . , . 10³ , , , , . 10² , . .

     

Radiation-induced reactions of cholesterol in an aqueous medium

⁶⁰Co -ray radiolysis of cholesterol /3-hydroxy-5-cholestene/ /I/ in the two-phase system /water-ethyl acetate/ and in the presence of air has been studied using TLC and GC methods. The following products were observed in the irradiated mixture: 3, 7-dihydroxy-5-cholestene /II/, G O. 36, 3-hydroxy-7-keto-5-cholestene /III/, G 1.48, 3-hydroxy-7-keto-5-cholestane /IV/, G 0.22, 3,5,6-trihydroxy-5-cholestane /V/, G 0.83, 5,6-epoxy-3-hydroxy-5-cholestane /VIa/, G 0.26, 5,6-epoxy-3-hydroxy-5-cholestane /VIb/, G 0.24, and 2, 3-dihydroxy-5-cholestene /VII/, G 0.22. The dose dependence of the formation of these products shows that the cholesterol derivatives substituted in the position 7 /II–IV/ are formed from a common precursor — the radical Ia. On the other hand, the products of the 5–C=C double bond reactions /V and VI/ are formed independently. Also the product VII is formed independently. A reaction scheme that is in agreement with these results is proposed.     

Glycosides of marine invertebrates. XII. Structure of a new triterpene oligoglycoside from holothurians of familyStichopodidae

From an ethanolic extract of the holothuriansStichopus chloronotus by column chromatography on silica gel a new triterpene oligoside has been isolated the structure of which has been established as 23(S)-acetoxy-3-{4-O-[O-(3-O-methyl--D-glucopyranosyl)-(13)--D-glucopyranosyl]-2-O-[O-(3-O-methyl--D-glucopyranosyl(-(13)-O--D-xylopyranosyl-(14)--D-glucopyranosyl]--D-xylopyranosyloxy}holost-7-ene. A hypothesis has been put forward concerning the biosynthesis of the carbohydrate chains in the glycosides of holothurians of the orderAspidochirota from bioside blocks.Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 200–204, March–April, 1982.     

Sterol glycosides from the Far Eastern holothurianCucumaria japonica

Sterol -D-xylopyranosides and arabinopyranosides in a ratio of 9:1 have been isolated from a lipid extract of the musculocutaneous sac of the Far Eastern holothurianC. japonica. The main components of both glycosidic fractions were identified as derivatives of cholesta-7,22-diene-3-ol, cholest-22-en-3-ol, 5-cholestan-3-ol, 24-ethylcholesta-7,22-dien-3-ol, and 24-methylene-, 24-methyl-, and 24-ethyl-cholest-22-en-3-ols.Institute of Immunology, Ministry of Health of the USSR, Moscow. M. M. Shemyakin Institute of Biorganic Chemistry, Academy of Sciences of the USSR, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 54, pp. 615–620, September–October, 1984.     

Ultrasonic study of the molecular encapsulation and the micellization processes of dodecylethyldimethylammonium bromide-water solutions in the presence of β-cyclodextrin or 2,6-di-o-methyl-β-cyclodextrin

Aqueous solutions of -cyclodextrin (-CD) or 2,6-di-o-methyl--cyclodextrin (DM--CD) and dodecylethyldimethylammonium bromide (D₁₂EDMAB) have been studied from speed of sound (u) data at 298.15 K, using a pulse-echo-overlap technique. The molecular encapsulation process of the surfactant monomer into the cyclodextrin cavity and its effect in the micellization process of the surfactant have been analyzed from theu measurements: I) as a function of [D₁₂EDMAB] in the presence of several initial cyclodextrin concentrations (-CD or.DM--CD); II) as a function of [cyclodextrin] (-CD or DM--CD), for an initial micellar solution of D₁₂EDMAB and; III) as a function of the [cyclodextrin]/[surfactant] stoichiometric concentrations. Both inclusion complexes formed (-CDD₁₂EDMAB) and (DM--CDD₁₂EDMAB) have stoichiometries of 11, and their association constantK have been determined using a model proposed in this work, based on the additivity of the different contributions of the involved species to the speed of sound. The apparent critical micellar concentration, cmc^*, of D₁₂EDMAB is found to increase linearly upon the addition of cyclodextrin (-CD or DM--CD). The free surfactant concentration in the micellar region, [D₁₂EDMAB]_f, decreases in the presence of -CD and slightly increases in the presence of DM--CD. The influence of the parcial methylation of the -cyclodextrin (-CDDM--CD) and of the polar head of the surfactant (D₁₂TAB D₁₂EDMAB) on the complextion and micellar parameters are also discussed.Supplementary material available: Tables of speed of sound (14 pages) are available from the authors.     

Steroids

Summary 1. A new type of steroido[17, 16-d]-3-(methyl, phenyl)isoxazoles has been synthesized by the cyclization of the syn-oximes of acylated 3-hydroxy-16, 17-oxidopregn-5-en-20-ones or their 5-saturated derivatives and acylated 17-benzoyl-3-hydroxy-16, 17-oxidoandrost-5-ones.2. It has been established that the Beckmann rearrangement of the anti-oximes of acylated 17-benzoyl-3-hydroxy-16, 17-androst-5-enes leads to a mixture of anilides and steroidoisoxazoles, which shows the inversion of the configuration of the oximes (from the anti to the syn form) during the rearrangement.Khimiya Prirodnykh Soedinenii, Vol. 2, No. 5, pp. 325–333, 1966     

Two new triterpene glycosides from the holothurian Duasmodactyla kurilensis

Two new glycosides have been isolated from the total triterpene glycosides of the holothurianDuasmodactyla kurilensis: kurilosides A (III) and C (IV). It has been established that (III) is 16-acetoxy-3-{[O--D-glucopyranosyl-(1 4)-O--D-quinovopyranosyl-(1 2)]-[O-(3-O-methyl--D-glucopyranosyl)-(1 3)-O-(6-O-(sodium sulfato)--D-glucopyranosyl)-(1 4)]--D-xylopyranosyloxy}-4,4,14-trimethylpregen-9(11)-en-20-one, while the minor glycoside (IV) is 16-acetoxy-3-{O--D-quinovopyranosyl-(1 2)-[O-(3-O-methyl--D-glucopyranosyl-(1 3)-O-(6-O-(sodium sulfato)--D-glucopyranosyl)-(1 4)]--D-xylopyranosyloxy}-4,4,14-trimethylpregn-9(11)-en-20-one.Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Branch, Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 221–226, March–April, 1991.     

Triterpene Glycosides of Fatsia japonica. VI. Structures of Glycosides D3a and D3b

Seeds of Fatsia japonica (Araliaceae) yielded the new glycosides of gypsogenin: 3-O--D-glucopyranosyl-(12)-O--D-glucopyranoside and 3-O--D-galactopyranosyl-(12)-O--D-glucopyranoside. The structures of these compounds were established by chemical methods and NMR spectroscopy.