A concise approach to both enantiomers of phytoprostane B1 type II

The synthesis of enantiomeric phytoprostane B₁ type II methyl esters has been accomplished in approximately 30% overall yield via two basic transformations starting from 3-[(dimethoxyphosphoryl)methyl]cyclopentenone as a key reagent. They include ethylation of the ring C(2) carbon and a Horner olefination reaction using the phosphonate moiety at C(3). The novel components of the Horner reaction, the enantiomeric methyl 9-formyl-9-hydroxynanoates, were easily prepared from racemic methyl 9-hydroxy-10-undecenoate via asymmetric Sharpless epoxidation (kinetic resolution) followed by ozonolysis.     

Cavity ring down spectroscopy: detection of trace amounts of substance

We describe several applications of cavity ring-down spectroscopy (CRDS) for trace matter detection. NO₂ sensor was constructed in our team using this technique and blue-violet lasers (395–440 nm). Its sensitivity is better than single ppb. CRDS at 627 nm was used for detection of NO₃. Successful monitoring of N₂O in air requires high precision mid-infrared spectroscopy. These sensors might be used for atmospheric purity monitoring as well as for explosives detection. Here, the spectroscopy on sharp vibronic molecular resonances is performed. Therefore the single mode lasers which can be tuned to selected molecular lines are used. Similarly, the spectroscopy at 936 nm was used for sensitive water vapour detection. The opportunity of construction of H₂O sensor reaching the sensitivity about 10 ppb is also discussed.     

THE STEREOCHEMISTRY OF DEALKYLATION STEP IN THE ARBUZOV REACTION INVOLVING FIVE-COORDINATE INTERMEDIATE. EVIDENCE FOR EQUILIBRIUM BETWEEN PHOSPHORANE AND PHOSPHONIUM SPECIES

Abstract

The oxidative addition of molecules X–Y to three-coordinated phosphorus compounds is of considerable general interest. If one of the groups attached to the phosphorus atom is an alkoxy, OR, the final product is almost always > P(O)Y with the formation of an alkyl halide RX. The above process is known as Arbuzov reaction, the mechanism of which can be represented, in the light of our present knowledge, as follows: mental mechanistic problem for the Arbuzov reaction.

The R(?)phosphite (4) was prepared from R(+)2-octanol of 95% opt. purity, [α]²⁰ _D + 9.4° (neat) and the chlorophosphite (3) by standard condensation in the presence of tertiary amine and purified by distilla tion in vacuo, δ³¹P ?127.5 ppm, [α]^D ₂₀ ?25.6° (neat). Equimolar amounts of the phosphite (4) and the corresponding halogen in CH2 C12 solution were allowed     

Phosphonates Containing Sulfur and Silicon: New Stereochemical and Mechanistic Aspects

Abstract

Synthesis, reactivity and conformation of cyclic S,S-thioacetals of formylphosphonates are described. The chemistry of α-trimethylsilyl-α-methylthiometanephosphonate is briefly discussed.     

α-Phosphoryl Cyclopentanones as Possible Intermediates in the Total Synthesis of Sarkomycin

Abstract

In an effort to synthesize sarkomycin 1 trans-2-diphenylphosphinoyl-3-tris (methylthio) methyl-cyclopentanone 7 and trans-2-diphenylphosphinoyl-3-carbo-methoxy-cyclopentanone 8 were prepared. The Horner-Wittig reaction of the latter with formaldehyde failed. (±)-Sarkonycin 1 was prepared by a sequence of reactions starting from diethyl 2-oxopropanephosphonate. The key steps in this synthesis involve the intramolecular carbenoid cyclization of 1-diazo-2-oxopropanephosphonate 10 and the Horner-Wittig reaction of 2-diethoxyphosphoryl-3-carboxy-cyclopentanone 12 with formaldehyde.     

A New View of the Mechanistic Pathways in the Iodine Atom Transfer Addition Reaction Involving 1-Iodoalkylphosphonates and Related Nonphosphorus Systems

The title reaction in the initiation step proceeds via two mechanistic pathways involving attack of the isobutyronitrile radical either on the starting iodide or on the starting alkene or alkyne followed by the reaction of the adduct radical with the iodide.     

SYNTHESIS AND TRANSFORMATIONS OF OPTICALLY ACTIVE α-PHOSPHORYL SULPHOXIDES

Abstract

As part of a continuing studies of α-phosphoryl sulphoxides, racemic dimethylphosphorylmethyl p-tolyl sulphoxide (1) was prepared and resolved into optical isomers. Sulphoxide (+)-1 with the R chirality at sulphur was synthesized stereospecifically by treatment of (?)-menthyl p-tolylsulphinate with dimethylphosphorylmethyllithium. This communication describes some transformations of optically active 1.     

The first stereoselective synthesis of optically active thiosulfinates

Treatment of optically active $\text{p}$-toluenesulfinamides (1) with thiols (2) in the presence of trifluoroacetic acid was found to give optically active $\text{p}$-toluenethio-sulfinates (3) with predominant inversion of configuration. Stereospecificity of this reaction varies from 30 to 80%. Some mechanistic aspects of the reaction are also discussed.     

Conversion of 1,3- into 1,4-dicarbonyl compounds by means of α-phosphoryl sulphides. Total synthesis of dihydrojasmone and methylenomycin B.

An effective synthesis of 1,4-dicarbonyl systems involving the Horner—Wittig reaction of α-phosphoryl sulphides with the half-protected 1,3-dicarbonyl compounds followed by hydrolysis of the vinyl sulphides formed is described. The total synthesis of dihydrojasmone and methylenomycin B employing this approach is reported.