Partially acetylated tri- and tetrarhamnoside dodecanyl ether derivatives from Cleistopholis patens

De novo asymmetric Achmatowicz approach to oligosaccharide natural products

The development and application of the asymmetric synthesis of oligosaccharides from achiral starting materials is reviewed. This de novo asymmetric approach centers around the use of asymmetric catalysis for the synthesis of optically pure furan alcohols in conjunction with Achmatowicz oxidative rearrangement for the synthesis of various pyranones. In addition, the use of a diastereoselective palladium-catalyzed glycosylation and subsequent diastereoselective post-glycosylation transformation was used for the synthesis of oligosaccharides. The application of this approach to oligosaccharide synthesis is discussed.

Production and Synthetic Modifications of Shikimic Acid

Shikimic acid is a natural product of industrial importance utilized as a precursor of the antiviral Tamiflu. It is nowadays produced in multihundred ton amounts from the extraction of star anise ( Illicium verum) or by fermentation processes. Apart from the production of Tamiflu, shikimic acid has gathered particular notoriety as its useful carbon backbone and inherent chirality provide extensive use as a versatile chiral precursor in organic synthesis. This review provides an overview of the main synthetic and microbial methods for production of shikimic acid and highlights selected methods for isolation from available plant sources. Furthermore, we have attempted to demonstrate the synthetic utility of shikimic acid by covering the most important synthetic modifications and related applications, namely, synthesis of Tamiflu and derivatives, synthetic manipulations of the main functional groups, and its use as biorenewable material and in total synthesis. Given its rich chemistry and availability, shikimic acid is undoubtedly a promising platform molecule for further exploration. Therefore, in the end, we outline some challenges and promising future directions.

Composition and Chemical Variability of Root Bark oil from Ivoirian Cleistopholis patens

The chemical composition of root bark oil of Cleistopholis patens (Benth.) Engl. & Diels from Côte d'Ivoire was determined by GC (in combination with retention indices), GC-MS and 13C NMR. The contents of the major compounds varied drastically from sample to sample: patchoulenone (0–70.5%), β-pinene (0–51.9%), bornyl acetate (0.5–31.2%), α-pinene (0.2–25.7%), juvenile hormone III (0.3–22.2%) and β-elemol (0–18.8%). Three chemical compositions may be differentiated, dominated by i) patchoulenone, ii) β-pinene and α-pinene, iii) juvenile hormone III, accompanied by bornyl acetate or β-elemol. 13C NMR data of patchoulenol (3-patchoulen-5- exo-ol) are reported.

Composition and Chemical Variability of Cleistopholis patens Trunk Bark Oil from Côte d'Ivoire

The chemical composition of trunk bark oil from Cleistopholis patens (Benth.) Engl. & Diels, growing wild in Côte d'Ivoire, has been investigated by GC (FID) in combination with retention indices, GC/MS and ¹³ C-NMR. Moreover, one oil sample has been subjected to CC and all the fractions analyzed by GC (RI) and ¹³ C-NMR. In total, 61 components have been identified, including various sesquiterpene esters scarcely found in essential oils. ¹³ C-NMR was particularly efficient for the identification of a component not eluted on GC and for the quantification of heat-sensitive compounds. Then, 36 oil samples, isolated from trunk bark harvested in six Ivoirian forests have been analyzed. The content of the main components varied drastically from sample to sample: (E)-β-caryophyllene (0.4 - 69.1%), β-pinene (0 - 57%), α-phellandrene (0 - 33.2%), α-pinene (0.1 - 30.6%), β-elemol (0.1 - 29.9%), germacrene D (0 - 25.4%), juvenile hormone III (0 - 22.9%), germacrene B (0 - 20.6%) and sabinene (tr-20.3%). Statistical analysis, hierarchical clustering and principal components analysis, carried out on the 36 compositions evidenced a fair chemical variability of the stem bark oil of this species. Indeed, three clusters have been distinguished: the composition of group I (ten samples) was dominated by β-pinene and α-pinene, group II (nine samples) was represented by α-phellandrene and p-cymene and group III (16 samples) by β-elemol. A sample displayed an atypical composition dominated by (E)-β-caryophyllene.

De novo asymmetric synthesis of the pyranoses: from monosaccharides to oligosaccharides

The various methods for the de novo asymmetric synthesis of the pyranose sugars are surveyed. The presentation begins with the work of Masamune and Sharpless with the use of the Sharpless asymmetric epoxidation for the synthesis of all eight l-hexoses. The development of other asymmetric reactions and their application for the synthesis of specific hexopyranoses are further discussed. The broad application of the Achmatowicz rearrangement with asymmetric catalysis, for the synthesis of various pyranones and imino sugars, is also presented. Finally, the use of a diastereoselective palladium-catalyzed glycosylation with the Achmatowicz approach for the synthesis of oligosaccharides and applications to medicinal chemistry are discussed.

Combined Analysis of the Root Bark Oil of Cleistopholis glauca by Chromatographic and Spectroscopic Techniques

The composition of root bark oil from Cleistopholis glauca Pierre ex Engler & Diels growing wild in Ivory Coast was investigated by GC (in combination with retention indices) and 13C NMR spectroscopy after partition of hydrocarbons and oxygenated compounds on silica gel. Thirty-one compounds have been identified. C. glauca produces a sesquiterpene-rich oil, patchoulenone (33.5%), cyperene (9.5%) and germacrene D (6.6%) being the main components. Special attention was paid to the identification and quantification of germacrene C (a heat-sensitive compound) and δ-elemene, which were achieved by a combination of GC(FID) and 13C NMR spectroscopy. The composition of C. glauca root bark and leaf oils differed drastically.

Analysis of Cleistopholis patens leaf and trunk bark oils using combined GC- flame ionisation detection, GC-retention index, GC-MS and (13) C-NMR

INTRODUCTION

Germacrenes A-C are secondary metabolites produced by various plants. They are sesquiterpene hydrocarbons bearing the (E,E)-1,5-cyclodecadiene structure known to undergo thermal rearrangement through a [3.3]-sigmatropic reaction. Such a rearrangement was evidenced by comparing the contents of a given germacrene and the corresponding elemene calculated by GC-flame ionisation detection (FID) with the relative intensities of the signals of both molecules in the (13) C-NMR spectrum of the mixture, recorded at room temperature.

OBJECTIVE

To develop a protocol to identify and quantify germacrenes A, B and C and in parallel the corresponding elemenes, using a combination of GC-FID and (13) C-NMR and then provide a correct analysis of Cleistopholis patens essential oils.

METHODS

The essential oil was submitted to GC-FID, GC-retention index, GC-MS and (13) C-NMR analyses. The relative percentages of every couple of germacrene and elemene measured by GC-FID were summed. Then, the relative ratio of the mean intensities of the signals of the protonated carbons of a given germacrene and the corresponding elemene was calculated. The contents of both compounds were obtained by combining GC-FID and (13) C-NMR data.

RESULTS

The true content of germacrene A/β-elemene, germacrene B/γ-elemene and germacrene C/δ-elemene in leaf and root oils from C. patens was evaluated by combination of GC-FID and (13) C-NMR data. Correct analysis of the essential oils was provided.

CONCLUSION

Combined analysis of essential oil including (13) C-NMR without isolation of the components, appeared really efficient to identify and quantify germacrene isomers and in parallel elemene isomers in essential oils.

Structure Activity Relationship Study of the Cleistriosides and Cleistetrosides for Antibacterial/Anticancer Activity

Two known cleistriosides and six known cleistetrosides were synthesized and evaluated for anticancer and antibacterial activity. This study, for the first time, reports anticancer activity and comprehensively the antibacterial activity for these oligosaccharide natural products. In addition, two new unnatural cleistetroside analogues were synthesized and tested. Biological activities for the ten oligosaccharides against B. subtilis were found to range between 4 and >64 µM, and for NCI-H460 human lung cancer epithelial cells between 7.5 and 90.9 µM. Similar activities were found for seven of the oligosaccharides against the NCI panel of 60 cell lines. The degree of acylation and location of the specific acetate groups had significant effects on the anticancer and antibacterial activity of both the cleistriosides and cleistetrosides.

Synthesis of several cleistrioside and cleistetroside natural products via a divergent de novo asymmetric approach

The de novo asymmetric syntheses of several partially acylated dodecanyl tri- and tetra-rhamnoside natural products (cleistriosides-5 and 6 and cleistetrosides-2 to 7) have been achieved (19-24 steps). The divergent route requires the use of three or less protecting groups. The asymmetry was derived via Noyori reduction of an acylfuran. The rhamno-stereochemistry was installed by a diastereoselective palladium-catalyzed glycosylation, ketone reduction and dihydroxylation.

Facile synthesis of cleistetroside-2, a partially acetylated oligorhamnoside from Cleistopholis glauca and patens

A tetrasaccharide, dodecanyl 4-O-acetyl-alpha-l-rhamnopyranosyl-(1-->3)-2,4-di-O-acetyl-alpha-l-rhamnopyranosyl-(1-->3)-4-O-acetyl-alpha-l-rhamnopyranosyl-(1-->4)-alpha-l-rhamnopyranoside (cleistetroside-2), was synthesized via '2+2' convergent strategy. Sequential regioselective 3-O-glycosylation of isopropyl 1-thio-alpha-l-rhamnopyranoside (4) with 4-O-acetyl-2,3-O-isopropylidene-alpha-l-rhamnopyranosyl trichloroacetimidate (8), and isopropyl 4-O-acetyl-2,3-O-isopropylidene-alpha-l-rhamnopyranosyl-(1-->3)-2,4-di-O-acetyl-alpha-l-1-thio-rhamnopyranoside (10) with dodecanyl 4-O-acetyl-alpha-l-rhamnopyranosyl-(1-->4)-2,3-O-isopropylidene-alpha-l-rhamnopyranoside (12), greatly facilitate the target availability.

Total synthesis of cleistetroside-2, partially acetylated dodecanyl tetrarhamnoside derivative isolated from Cleistopholis patens and Cleistopholis glauca

The total synthesis of a partially acetylated dodecanyl tetrarhamnoside derivative, cleistetroside-2, which was isolated from Cleistopholis patens and Cleistopholis glauca and showed significant in vitro antibacterial activity against the Gram-positive bacteria, was achieved for the first time.

Chemical Constituents from Alnus formosana Burk. II. Polar Constituents from the Leaves

This study was aimed to explore the n-BuOH soluble constituents of the leaves of Alnus formosana Burk. A total of 13 compounds were isolated and characterized. Of these, 2″'-cinnamoyloregonin is a new diaryl heptanoid glycoside. Ten of the remaining twelve known compounds, i.e. platyphylloside, aceroside VII, myzodendrone, quercetin, kaempferol-3-O-rhamnoside, quercetin-3-O-rhamnoside, quercetin-3-O-glucoside, rhamnetin-3-O-rhamnoside, inositol, and shikimic acid, are reported for the first time for an Alnus species. The structures were characterized by spectral analysis.

Two New Glycosides from the Soft Coral Sinularia firma

Two new glycosides, named Firmacosides A and B, together with known fatty esters, batyl alcohol, Delta(5,20) sterol and sphingosine derivatives have been isolated from the soft coral Sinularia firma TIX-DUR. On the basis of spectroscopic analysis ((1)H-NMR, (13)C-NMR, (1)H-(1)H COSY, HMQC, HMBC and FAB-MS), Firmacoside A was established as hexadecanyl-1-O-alpha-D-arabinopyranosyloxy (1-->4)-alpha-D-arabinopyranosyloxy (1-->4)-alpha-D-arabinopyranoside (1), and firmacoside B was elucidated as docosanyl-1-O-alpha-D-arabinopyranosyloxy (1-->4)-3-O-acetyl-alpha-arabinopyranosyloxy (1-->4)-alpha-D-arabinopyranoside (2).