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This note describes the synthesis of different alkenylated carbohydrate derivatives suitable for direct attachment to hydrogen-terminated silicon surfaces. The derivatives were alkenylated at the C-1 position, while the remaining hydroxyl groups were protected. The development of such new carbohydrate-based sensing elements opens the access to new classes of biosensors.

The copper catalysed conjugate addition of methyl magnesium iodide to cyclohexenones and trapping of the enolate as its trimethylsilyl enol ether, followed by a trityl hexachloroantimonate (TrSbCl6) catalysed Mukaiyama-reaction, was applied to R-(−)-carvone. This proved to be an efficient method for the preparation of C-2, C-3 functionalised chiral cyclohexanones. These compounds were converted into their α-cyano ketones, which were submitted to Robinson annulation reactions with methyl vinyl ketone. The scope and limitations of these annulations were investigated. A series of highly functionalised chiral decalones were obtained that can be used as starting compounds in the total syntheses of enantiomerically pure clerodanes.

The first total synthesis of the natural enantiomer of the insect-antifeedant dihydroclerodin (1) and lupulin C (40) has been achieved starting from (R)-(−)-carvone (2). In the applied strategy, the hexahydrofuro[2,3-b]furan moiety was introduced in an early stage of the synthesis. The correct configuration at C-9, C-11, C-13, and C-16 was established by application of a remarkably diastereoselective Mukaiyama reaction. The desired configuration at C-10 was obtained by catalytic reduction of the intermediate enone 21. After annulation of the second ring, the structural features at C-4, C-5, and C-6 were introduced. The successful finishing of the synthesis included a Chugaev elimination to give the exocyclic double bond at C-4 that is present in lupulin C. Oxidation of this double bond with m-CPBA afforded dihydroclerodin.

The introduction of a hydroxy group at C-13 of the clerodane skeleton is proposed as a strategy to potentially increase the antifeedant activity of simple analogs. This idea is applied to clerodane analogs with furan or butenolide type sidechains and therefore syntheses were developed for several types of 3-alkyl-substituted butenolides, 3-alkyl-substituted-3-hydroxybutenolides and 3-hydroxytetrahydrofuran derivatives. The antifeedant activity was tested on 5th instar larvae of Pieris brassicae .

The monoalcohols (−)-globulol ( 2 ), (−)-epiglobulol ( 3 ), (−)-ledol ( 4 ), and (+)-viridiflorol ( 5 ) were synthesized from (+)-aromadendrene ( 1 ). The cis-fused alloaromandedrone ( 14 ), the key intermediate used in the synthesis of 4 and 5 , was obtained from the trans-fused apoaromadendrone ( 13 ) via a selective protonation of the thermodynamic enol trimethylsilylether 15 . After hydroxylation of the tertiary C11 of 13 with RuO 4 , (+)-spathulenol ( 6 ), (−)-allospathulenol ( 7 ), and the aromadendrane diols 8 – 11 could be prepared. Compounds 2 – 11 were tested for antifungal properties, but their activity was only moderate.

Starting from the readily available chiral synthon 5 the sesquiterpene ether (−)-kessane (1) can be synthesized in a 9 steps reaction sequence in an overall yield of 43%.

Copper (I) catalysed conjugate addition of methylmagnesium iodide to R-(−)-carvone and trapping the enolate as its trimethylsilyl enol ether, followed by a trityl perchlorate (TrClO4) catalysed Mukaiyama-aldol reaction, is an efficient method for the preparation of highly functionalised cyclohexanones which can be used as starting compounds in the total syntheses of enantiomerically pure clerodanes.

This paper presents the first functionalization of silicon surfaces with well-defined, covalently attached monolayers containing saccharides. Two methods were used to this aim: a thermal method (refluxing in mesitylene) and a recently developed, extremely mild photochemical method (irradiation with 447 nm at room temperature). The results were analyzed by FT-IR and angle-resolved X-ray photoelectron spectroscopy. The use of a two-dimensional detector in ARXPS allows for unparalleled, subnanometer resolution in the determination of the elemental composition of monolayers. Even for monolayers with a total thickness of only approximately 1.5 nm, a clear elemental depth profile can be obtained. Such analyses display for sialic acid-containing monolayers that the mild photochemical attachment does not destroy the (rather fragile) sialic acid moiety and that the sugar is present at the top of the monolayer and thus available for biological interactions.

The total synthesis of neohedycaryol (4), the C(9)-C(10) double bond regioisomer of the germacrane sesquiterpene hedycaryol, was accomplished in 10 steps from the known dione 6. A Marshall fragmentation of the intermediate mesylate 14 was used to prepare the trans,trans-cyclodeca-1,6-diene ring present in neohedycaryol. During the synthesis of 14, a pronounced example of through-bond interactions (TBI) was observed. The preferred elongated chair conformation of neohedycaryol was demonstrated spectroscopically and by chemical conversion into alpha-, beta-, and gamma-eudesmol. These findings indicate that the occurrence of neohedycaryol as a precursor in the biosynthesis of epi-eudesmanes as proposed in the literature is unlikely. The preference of neohedycaryol for the elongated chair conformation further shows that the compound occupies the meso form. This implies that neohedycaryol may act as a precursor in the biosynthesis of both ent- and usual eudesmanes.

(-)-Apoaromadendrone (3) can be obtained easily in large quantities from (+)-aromadendrene which is the main constituent in a commercially available distillation tail of the oil of Eucalyptus globules. Acid catalyzed selective cleavage of the C3-C4 bond of the cyclopropane ring in 3 gave (-)-isoapoaromadendrone(9) in high yield. The regioselectivity of the cyclopropane ring opening was proved by NMR spectroscopy in combination with chemical transformations. Ozonolysis of 9 afforded the keto alcohol 14 which is a suitable chiral intermediate for the syntheses of guaianes and guaianolides.