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The first synthesis of a nucleoside analogue 1 is reported wherein the nucleobase 5-fluorocytosine is attached to a 1,6-dioxaspiro[5.5]undecane spiroacetal ring system. The spiroacetal system acts as a substitute for the sugar unit of natural nucleosides and provides a conformationally restricted framework upon which to append nucleobases in a well defined geometry. Trimethylsilyl triflate promoted Vorbrüggen-type coupling of bis(trimethylsilyl)-5-fluorocytosine 3 with spiroacetal acetate 2 provided spiroacetal nucleoside 1 in which the nucleobase occupied an equatorial position together with the ring opened (Z)-alkene 10. Spiroacetal acetate 2 serves as the spiroacetal donor and was prepared from the readily available starting materials δ-valerolactone and but-3-yn-1-ol 4.

(S)-Butane-1,2,4-triol (2) has been investigated as a potential chiral auxiliary for the formation of non-racemic acetals derived from η6-arylcarbonyl complexes of tricarbonylchromium. Predominantly the cisdioxan (5) was formed from benzaldehyde, leading to preparation of the η6-Cr(CO)3complex (16), and of the derived complexes (23) and (24). Lithiation{electrophile quenching of these complexes gave a mixture of products arising fromorthoand benzylic functionalization. Reaction of acetophenone, or of the η6-Cr(CO)3complexes (45) or (46), with either the triol (2) or its tris(silyl) ether (15) under conditions of kinetic or thermodynamic control gave an inseparable mixture of acetals.

Methods for the oxidation of the aryl ring of derivatives of podocarpic acid have been examined. Oxidation of methyl 12-hydroxypodocarpa-8,11,13-trien-19-oate (2) with phenyliodonium diacetate in various solvents gives 8β-substituted dienones. An 8β-chloro dienone is formed during oxidation of the phenol (2) with t-butyl hypochlorite. Oxidation of (2) with dimethyldioxiran gives mainly the 7-ketone (13) but also affords the novel ε-lactone (26), while treatment with ruthenium tetraoxide also affords products of benzylic oxidation. Oxidation of methyl podocarpa-8,11,13-trien-19-oate (4) with m-chloroperbenzoic acid affords a B-ring lactone (29) and, unexpectedly, a 6α-chloro 7-ketone (30). The action of cerium(IV) ammonium nitrate on (2) gives nitro derivatives rather than oxidation products. Oxidation of methyl 12-hydroxy-13-methoxypodocarpa-8,11,13-trien-19-oate (22) with m-chloroperbenzoic acid gives a low yield of a 7-oxo derivative (17) while treatment with ozone gives an unusual α,β-unsaturated γ-lactone (31), the hydroxy lactone (33), the unsaturated keto ester (34), and the substituted furan (35). Oxidation of (22) with Fremy"s salt gives products of ring B oxidation. The structure of (31) has been confirmed by X-ray crystallography.

Attempts to alkylate products from Birch reductions of derivatives of podocarpic acid are reported. Attempted reductive silylation of ring C of methyl 12-methoxypodocarpa-8,11,13-trien-19-oate (5) gives products of C4 ester reduction only. The enantiopure form of the bis(ethylene acetal) (15) of 19-norpodocarp-8-ene-3,12-dione, a potentially useful intermediate for quassinoid synthesis, has been prepared from the ketone (34). Functionality at C8 on the β-face has been successfully introduced by abnormal Reimer–Tiemann reactions of podocarpic acid (2) and its 13-methyl derivative (10). The saturated ketone (48) has been converted into an α,β-unsaturated ketone (18) which has potential for introducing functionality at C14.

Tetra- N-methyl(2-hydroxynaphthylmethyl)aminomethyl resorcinarene 5has been synthesised either from tetrabenzoxazine resorcinarene 2and 2-naphthol or from the C-methyl resorcinarene 1and naphthoxazine 6. Reaction of the tetrabenzoxazine resorcinarene 2with C-methyl resorcinarene 1is proposed to give carceplex 7.

The stereoselective synthesis of a number of (η6-arene)tricarbonylchromium(0) complexes derived from podocarpic acid has been achieved in good to excellent yield. The stereochemistry of complexes 36and 37was established by X-ray crystallography. Reactions of some of the deprotonated complexes with electrophiles were investigated.

Reaction of 7-oxototara-8,11,13-trien-13-yl acetate (3) with acetic anhydride-perchloric acid affords the γ-pyrone (8) in addition to the previously reported acetyl derivative (4). Baeyer–Villiger oxidations of the ketones (3) or (5) have given starting material or complex mixtures, but the ε-lactone (9) and the rearranged product (11) were isolated from two experiments with (3). Oxidation of 13-methoxytotara-8,11,13-triene (2) with Jones reagent gives the 7-oxo derivative (5) and a low yield of a ring B opened substituted p-benzoquinone (13). Pathways to (11) and (13) are proposed.

The iodination of thallium(I) salts of phenols is examined and the results are compared with those of the selective ortho-iodinating reagent thallium(I) acetate-iodine.

Several series of stilbene derivatives for possible use as smart additives in polymers used as packaging films have been prepared and characterized. Differential scanning calorimetry was performed on some of the stilbenes in order to determine any liquid crystal properties. Those compounds which had multiple phase transitions were also shown to have two liquid crystalline phases according to optical microscopy.

Feist-Benary condensations1,2 to form furans are usually carried out by reacting an á-halo aldehyde and a β-keto ester under basic conditions. However, yields are often poor, and the main product is often a dihydrofuranol3 requiring subsequent acid-catalysed dehydration to form the furan. The α-halo acetaldehyde is also difficult to prepare free of water when anhydrous reaction conditions are desired.

The thermally promoted reactions of some phenyl and diterpenoid η 2-(2-acylaryl-C,O)tetracarbonylmanganese (I) complexes with phenyl vinyl sulfone, methyl vinyl sulfone, or phenyl vinyl sulfoxide, have been investigated. The major products from the diterpenoid complexes arise from insertion followed by reductive demetallation; cyclopenta-annulation, when it occurs, is a minor process. Liberation of the metal-free adducts from their Mn-containing precursors requires treatment with either acid or photolysis-oxidation.

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The Si−N distance in the five-coordinate silatranyl complex Os(Si{OCH2CH2}3N)Cl(CQ)(PPh3)2 (1a, Q = O) is very long, and the geometry about nitrogen is planar. Accordingly, the nitrogen atom readily undergoes methylation or protonation, and this increases the Si−N separation even further. On addition of CO to 1b (Q = S), the coordinated CS inserts into the Os−Si bond and the normal silatrane N−Si interaction is restored in the product, Os(η²-C{S}Si{OCH2CH2}3N)Cl(CO)(PPh3)2 (4).

Reactions of alkoxyarene-chromium tricarbonyl complexes, having chiral alkoxy groups, with isobutyronitrile anion, followed by standard work-up produces substituted alkoxycyclohexadienes with diastereomeric excesses of up to 76%. Conversion to cyclohexenones allows recovery of the chiral alcohol auxiliary. The absolute stereochemistry of the product from the optimum procedure was determined by using Mosher's method on the derived cyclohexenol.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Oxidative coupling of deoxypodorhizon (I) with Tl2O3may be controlled to give either deoxyisopodophyllotoxin (II) or isostegane (III).

Oxidative coupling of the racemic monophenolic monoester (I) gives the aryltetralin (II), which is a potential intermediate for the synthesis of clinically active monophenolic lignan lactones.