Oxidative transformations of labdane diols. III. Preparation of acids with a strobane skeleton from larixol

It has been shown that the oxidation of larixol with chromic acid mixture forms methyl 6-oxo-8α,13α-epoxystroban-14β-oate, methyl 6-oxo-8α,13α-epoxystroban-14α-oate, and 6,13-dioxo-14,15-bisnorlabd-7-en-17-oate.     

Oxidative transformations of cembrane diterpenoids III. Epoxycembrenes

Summary 1. It has been established that the epoxidation of cembrene with perbenzoic and peracetic acids takes place stereospecifically at each of the trisubstituted double bonds with the formation of 4S,5R-, 7S,8S-, and 11S,12S-monoepoxycembrenes, the structures and absolute configurations of which have been established by spectral methods.2. Epoxidation of cembrene at the C₁₁–C₁₂ double bonds under the conditions used takes place preferentially as compared with epoxidation at the C₇–C₈ double bond.Novosibirsk Institute of Organic Chemistry, Siberian Branch of the Academy of Sciences of the USSR. Novosibirsk State University. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 525–531, July–August, 1977.     

Ionization constants of boronic acids and their complexation with diols

Ionization constants of a number of boronic acids were determined spectrophotometrically in aqueous solutions. The effect of different substituents on their acid properties is considered. The strongest acids are shown to be phenylboronic acid derivatives containing a nitro group. A model study of the interaction between boronic acids and polyvinyl alcohol depending on pH is analyzed to reveal the optimum conditions for the formation of a stable boronate-diol complex.     

Oxidative transformations of cembrane diterpenoids I. Oxidation of cembrene with chromium trioxide

Summary 1. The oxidation of cembrene with chromium trioxide in aqueous sulfuric acid (the Jones reagent) and in aqueous acetone has given norcembra-2,7,11-trien-4-one, norsolanadione, (3E, 8E)-5-isopropyl-8-methyltrideca-3,8-diene-2,12-dione, and five new compounds the structures of which have been established on the basis of their spectra.2. Oxidation with chromium trioxide in aqueous acetone, in contrast to oxidation with the Jones reagent, takes place stereospecifically—the C₁₁-C₁₂ double bond of cembrene is not affected.Novosibirsk Institute of Organic Chemistry, Siberian Branch of the Academy of Sciences of the USSR. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 313–320, May–June, 1976.     

Oxidative transformations of cembrane diterpenoids I. Oxidation of cembrene with chromium trioxide

1. The oxidation of cembrene with chromium trioxide in aqueous sulfuric acid (the Jones reagent) and in aqueous acetone has given norcembra-2,7,11-trien-4-one, norsolanadione, (3E, 8E)-5-isopropyl-8-methyltrideca-3,8-diene-2,12-dione, and five new compounds the structures of which have been established on the basis of their spectra. 2. Oxidation with chromium trioxide in aqueous acetone, in contrast to oxidation with the Jones reagent, takes place stereospecifically—the C₁₁-C₁₂ double bond of cembrene is not affected.     

Synthetic transformations of higher terpenoids: XVII. Intramolecular cyclization of N-furfuryl amides of the labdane series

16-(Benzylaminomethyl)lambertianic acid methyl ester reacts with 2-methylprop-2-enoyl chloride to give unsaturated amide which readily undergoes intramolecular [4 + 2]-cycloaddition with formation of terpenoid derivatives of 10-oxa-3-azatricyclo[5.2.1.0^1,5]decenone. Acetylation of lambertianic acid methyl ester with acetic anhydride occurs preferentially at the 2-position of the furan ring and is accompanied by migration of the exocyclic double bond. Reductive amination of 16-acetyl-15,16-epoxylabda-8(9),13,14-triene and subsequent reaction of the resulting amine with 2-methylprop-2-enoyl chloride give intramolecular cyclization products in high yield without isolation of intermediate furfurylacryloyl derivative. Reactions of methyl 16-(benzylaminomethyl)-15,16-epoxylabda-8(9),13,14- and -8(17),13,14-trien-18-oates with maleic anhydride lead to the formation of the corresponding 10-oxa-3-azatricyclo[5.2.1.0^1,5]dec-8-ene-6-carboxylic acid derivatives as mixtures of diastereoisomers.     

Oxidative transformations of cembrane diterpenoids. VI. Epoxidation of isocembrol

The stereochemistry of the epoxidation of the diterpene alcohol isocembrol has been studied. The main direction of attack of peracids is the C₁₁ double bond of isocembrol, with the predominant formation of the 11S,12S-epoxide. The ratio of the monoepoxyisocembrols does not change appreciably with a variation in the temperature of the reaction or in the peracid used. 11S,12S-Epoxyisocembrol has been isolated as a natural product from the oleoresin of the Siberian stone pine.Novosibirsk Institute of Organic Chemistry, Siberian Branch, Academy of Sciences of the USSR. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 581–587, September–October, 1983.     

Polycondensations of dicarboxylic acids and diols derived from optically active amino alcohols

Polycondensations of dicarboxylic acids with diols having amide moieties derived from optically active amino alcohols were carried out. Polymers with M _ns 8,700–17,400 were obtained by the polycondensations using 1.2 eq. of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC·HCl) in DMF at room temperature for 8 h in satisfactory yields. The T_g of the polymer rose with decrease of the methylene chain length of the dicarboxylic acid. In the T_gs of the polymers from L-leucinol, even-odd effect was observed with increase of the methylene chain length of the dicarboxylic acid. The molecular rotation values of the polymers were constant except for the polymer from succinic acid, which showed the negatively largest one. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2925–2934, 1997     

Oxidative transformations of cembrane diterpenoids IV. Photooxidation of cembrene

The photooxidation of cembrene by singlet oxygen is a stereoselective reaction and it is stereochemically similar to the epoxidation of cembrene by peracids. From the mixture of the photooxidation products of cembrene after its treatment with sodium tetrahydroborate four allyl alcohols have been isolated and the structures of two of them, previously undescribed, have been established on the basis of their spectral characteristics. The main component of these alcohols is cembra-2E, 4Z, 7E, 10E-tetraen-12S-ol.Novosibirsk Institute of Organic Chemistry, Siberian Branch, Academy of Sciences of the USSR. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 60–67, January–February, 1981.     

Efficient assembly of chromone skeleton from 2,3-allenoic acids and benzynes

Chromone derivatives were synthesized from 2,3-allenoic acids and benzynes in moderate to excellent yields under mild conditions. Instead of the cyclic conjugate addition of the intermediate A formed by the nucleophilic addition of allenoic acid with benzyne, this intermediate undergoes 1,2-addition with the carbonyl group, which was followed by the ring opening, conjugate addition, and protonolysis to afford chromone derivatives. This protocol allows the diversity due to the substituent-loading capability of 2,3-allenoic acids as well as benzynes.     

Oxidative transformations of cembrane diterpenoids. II. Cembra-2,7,11-triene-4,5-diols

Summary 1. The oxidation of cembrene with chromium trioxide in aqueous acetone forms, together with other compounds, the products of its hydroxylation at the C₄ double bond — cembra-2,-7,11-triene-4,5-diols epimeric at the C₄ double bond.2. On the basis of chemical and spectral characteristics, it has been established that these diols have the 4S, 5R and 4R, 5R configurations, respectively.Novosibirsk Institute of Organic Chemistry, Siberian Branch of the Academy of Sciences of the USSR, and Novosibirsk State University. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 54–59, January–February, 1977.