Synthesis of a substituted 6,8-dioxabicyclo[3.2.1]octane

Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 692–693, May, 1991.     

Cationic polymerization of 6,8-dioxabicyclo-[3.2.1]octane and 3,6,8-trioxabicyclo[3.2.1]octane

6,8-Dioxabicyclooctane (DBO) and 3,6,8-trioxabicyclooctane (TBO) underwent ring-opening polymerization when treated with PF₅ in dichloromethane at ?78°C. These conditions were outstandingly effective for the polymerization of these bicyclic monomers, as shown by systematic variation of catalyst, solvent, and temperature. Best results were 68–84% yields of poly-DBO, η_inh 0.26–0.33 dl/g, and ～100% yield of poly-TBO, η_inh 0.56–0.80 dl/g. The relationship of these results to those of previous investigators of DBO discussed.     

Intramolecular hydrogen abstraction reaction promoted by alkoxy radicals in carbohydrates. Synthesis of chiral 2,7-dioxabicyclo[2.2.1]heptane and 6,8-dioxabicyclo[3.2.1]octane ring systems

The reaction of specifically protected anhydroalditols with (diacetoxyiodo)benzene or iodosylbenzene and iodine is a mild and selective procedure for the synthesis of chiral 6,8-dioxabicyclo[3.2.1]octane and 2,7-dioxabicyclo[2.2.1]heptane ring systems under neutral conditions. This reaction can be considered to be an intramolecular glycosidation that goes through an intramolecular hydrogen abstraction promoted by an alkoxy radical followed by oxidation of the transient C-radical intermediate to an oxycarbenium ion. This methodology is useful not only for the preparation of chiral synthons but also for the selective oxidation of specific carbons of the carbohydrate skeleton, constituting a good procedure for the synthesis of protected uloses.     

Vibrational circular dichroism DFT study on bicyclo[3.3.0]octane derivatives

The absolute configurations of four bicylco[3.3.0]octane derivatives: endo-bicyclo[3.3.0]octane-2,6-diol, endo-2,6-diacetoxybicyclo[3.3.0]octane, endo-bicyclo[3.3.0]octane-2,6-dione and bicyclo[3.3.0]octa-2,6-dien-2,6-bistriflate were studied by vibrational circular dichroism (VCD). These chiral derivates are of interest as intermediates in the asymmetric synthesis of enantiomerically pure natural products and chiral ligands for asymmetric catalysis. VCD has been used to determine the absolute configuration of each compound, proving the capability of VCD for molecules with several stereogenic centres. IR and VCD spectra have been simulated at the B3LYP/6-31G¹ level for all possible diastereomers. Based on the agreement between the experimental and the calculated spectrum, the stereochemistry of each compound could be assigned. The predicted absolute configurations are found to agree with literature data.     

Determining the absolute configuration of exo-7 derivatives of 5-methyl-6,8-dioxabicyclo[3.2.1]octane by VCD

The VCD spectra in the region of 1100–1400 cm⁻¹ of four derivatives of 5-methyl-6,8-dioxabicyclco[3.2.1]octane reveal common features which indicate the absolute configuration of the bicyclic ketal ring system. One of these in particular can serve as a more general configurational marker for the chiral unit-CH(CH₂R)X-, X = O and S, when contained in different size ring molecules.     

Synthesis of chiral 1,2-diols and related compounds of biological activities via stepwise ring fission of 5-alkyl-6,8-dioxabicyclo[3.2.1]octane skeleton

5-Alkyl-7-mesyloxymethyl-6,8-dioxabicyclo[3.2.1]octanes , prepared from (+)-tartaric acid, were converted by means of an organoaluminium reagent Et₂AlSPh into the pyranoid monothioacetals, which were utilized via the successive thioacetalization to the synthesis of the insect pheromones (+)-disparlure and (−)-(2S,3S)-octanediol.     

Concise asymmetric synthesis of (5R)-6-hydroxy-3,8-dioxabicyclo[3.2.1]octane derivatives

[reaction: see text] A concise method to asymmetrically synthesize 6-hydroxy-3,8-dioxabicyclo[3.2.1]octane (HDBO) derivatives was devised.     

Unfolding the frontalin chemistry: a facile selective hydrogenation of 7-methylidene-6,8-dioxabicyclo[3.2.1]octanes, 2:2 ensembles of ketones and acetylene

1. Download high-res image (130KB)
2. Download full-size image

     

Oxidative and hydrolytic cleavage of cyclopropane and spirocyclobutane derivatives of 6,8-dioxabicyclo[3.2.1]octane,the products of transformation of levoglucosenone

A new method for the synthesis of (1R,4S,5S)-4-hydroxymethyl-3-oxabicyclo[3.1.0]hexan2-one, the cyclopropane analog of (S)-5-hydroxypent-2-en-4-olide, has been suggested based on oxidation of (1S,2S,4R,6R)-7,9-dioxatricyclo[4.2.1.0^2,4]nonan-5-one. Oxidation of cyclobutanones, spirojoined with the fragments of 6,8-dioxabicyclo[3.2.1]oct-2-ene, 6,8-dioxabicyclo[3.2.1]octane (at position 4), or 7,9-dioxatricyclo[4.2.1.0^2,4]nonane (at position 5), upon the action of m-chloroperoxybenzoic acid or the KMnO₄-H₂SO₄-H₂O system leads to the corresponding spirojoined butanolides in 73–85% yields. The same cyclobutanones easily undergo the four-membered ring opening upon the action of dilute H₂SO₄ at 50–90 °C to form 6,8-dioxabicyclo[3.2.1]octane-4- or 7,9-dioxatricyclo[4.2.1.0^2,4]nonane-5-propionic acid.     

Ready access to the 6,8-dioxabicyclo[3.2.1]octane ring system using asymmetric heterocycloaddition induced by a chiral sulfoxide: application to the total synthesis of the Mus musculus pheromone

A new stereocontrolled total synthesis of the (1R,5S,7R)-exo-6,8-dioxabicyclo[3.2.1]oct-3-ene skeleton of the Mus musculus pheromone has been achieved via an asymmetric intermolecular Diels–Alder reaction and an intramolecular conjugated addition, controlled by a chiral auxiliary.     

Enantiospecific synthesis of 3-aza-6,8-dioxa-bicyclo[3.2.1]octane carboxylic acids from erythrose

New methodology for the synthesis of enantiopure 3-aza-6,8-dioxa-bicyclo[3.2.1]octane-carboxylic acids belonging to 7-endo-BTAa sub-class of γ/δ amino acids is described. The novelty is the use of 2,3-O-isopropylidene-erythrose instead of meso-tartaric acid derivative, thus allowing us to perform an enantiospecific synthesis. Reductive amination of erythrolactol with aminoacetaldehyde diethylacetal or benzylamine, and subsequent acid cyclisation gave directly the amino alcohol scaffold. Protection of nitrogen as urethane and final alcohol oxidation afforded the Fmoc-, Boc-, and Cbz-amino acids. The new synthetic route was applied to multigram scale, thus resulting in a marked improvement of the synthesis of enantiopure 7-endo-BTG and 7-endo-BTK amino acids.     

Natural polyene pyrones. Synthesis of the 2,6-dioxabicyclo[3.2.1]octane unit of citreoviridinol

The 2,6-dioxabicyclo[3.2.1]octane unit, $\text{viz}$ 10, present in citreoviridinol (1) has been produced in a stereoselective manner by treatment of the epoxide (8) derived from citreoviral (6), $\text{via}$ (7), with $\text{p}$-toluenesulphonic acid.     

Selective transformation reaction of 6,8-dioxabicyclo[3.2.1]octane structure to δ,ε-enone and application to the synthesis of Douglas-fir tussock moth pheromone

Lewis acid induced C-O bond cleavage of a bicyclic ketal compound using AcCl-NaI produced a mixture of δ,ε-enone, allylic acetate and diacetate derivatives via a common 5-membered acetoxonium intermediate. A selective method to the synthesis of δ,ε-enone in high yield was introduced and applied to the synthesis of Douglas-fir tussock moth pheromone.