Lyme disease is a multisystemic disorder caused by infection with Borrelia burgdorferi sensu lato which is carried by ticks of the Ixodes ricinus complex. The agent was discovered in 1982 in North America and the disease is recognized as an emerging infectious diseases in North America and Europe. Japanese Borrelia isolates were characterized by genetic and immunologic analysis. Isolates from Ixodes ovatus were found to be unique by DNA/DNA hybridization analysis, restriction fragment length polymorphism analyses of the flagellin gene and the 16S rRNA genes, and were described as new species, Borrelia japonica. Isolates from Ixodes persulcatus were determined as Borrelia garinii and Borrelia afzelii. However, B. garinii found in Japan was different from those from Europe in immunologic and genetic characteristics of outer surface protein A, but B. afzelii isolates from Japan and Europe were identical. An experimental model of arthritis related to Lyme disease using outbred ddY mice was established. Whole cell vaccine prepared from North American and European isolates could not elicit protective immunity against infection of Japanese isolates. This implies that vaccine development using Japanese isolates is necessary. Borrelia bound specifically to galactosylceramide (GalCer), glucosylceramide and lactosylceramide which are present in various types of cells as binding receptor, but not to other glycosphingolipids. Furthermore, the infectivity of Borrelia may be associated with the binding to glycosphingolipids on the cell surface and a 67 kilodalton protein of Lyme disease Borrelia may be involved in binding of Borrelia to GalCer.
Both enantiomers of cis-4, 5-disubstituted 2-oxazolidinones, DHAOx (4, 5-(9, 10-dihydroanthraceno)oxazolidin-2-one), DMAOx (4, 5-(9, 10-dihydro-9, 10-dimethylanthraceno)oxazolidin-2-one), CPAOx (4, 5-(1, 4-cyclopentano)oxazolidin-2-one), HMCOx (4, 5-[3, 5-(1, 2, 3, 4, 4, 5-hexamethyl-1, 4-cyclopenteno)]-oxazolidin-2-one) and BPSOx (4, 5-[1, 4(2-terf-butyldiphenylsilyloxy)cyclopenteno] oxazolidine-2-one), which are sterically congested and conformationally fixed by bicyclo [2.2.1] and [2.2.2] ring systems are newly prepared by the Diels-Alder reactions of 2-oxazolone with the cyclic dienes such as anthracenes and cyclopentadienes followed by optical resolution with MAC acid (2-methoxy-1-apocamphanecarboxylic acid). These compounds, particularly DMAOx, HMCOx and BPSOx, serve well as the most powerful 2-oxazolidinone chiral auxiliaries reported so far for the asymmetric reactions such as alkylations, the Diels-Alder reactions, the Michael-type additions and aldol reactions. Sterically congested 2-aminoalcohol derivatives derived from the ringopening of these 2-oxazolidinones are shown to be highly useful auxiliaries for enantioselective additions of diethylzinc to aldehydes and enantiodivergent canversion of meso-dicarboxylic anhydrides to chiral half-esters.
A stable cation radical Weitz' aminium salt, tris (4-bromophenyl) aminium hexachloroantimonate (BAHA) initiated electron transfer has been found to efficiently promote a great variety of reactions on electron-rich substrates : e.g. the cation radical pericyclic reactions, the chain-induced cation radical oxygenation of strained olefines and dienes, and several other intriguing reactions on a great variety of electron-rich substrate. The discovery of the Weitz' aminium salt catalysed Diels -Alder reaction has stimulated interest in cation radical chemistry and facilitated the developement of a wide range of cation radical pericyclic chemistry. Applications of the method to the synthesis of natural products utilizing BAHA are also presented. Reaction of a lignan precursor, cinnamyl alcohols with BAHA in tetrahydrofuran (THF) gave a furofuran lignan, (±)-sesamin in one step. Podophyllum lignans, (±)-isopodophyllotoxin and (±)-isopicropodophyllin were synthesized by a biomimetic procedure from the doubly unsaturated esters by means of the BAHA induced cation-radical cycloaddition reaction. A new general synthesis for (±)-dibenzocyclooctadiene lignans was established utilizing novel synthetic method for quinone derivatives by oxidation with BAHA. Reactions of phenol derivatives using BAHA gave the corresponding quinone derivatives, which may be useful synthon for obtaining quassinoids such as quassin.
This review describes a highly efficient [3+2] annulation based on the Brook rearrangement for functionalized cyclopentenols, which we have recently developed, and its application to the synthesis of natural products.