Synthesis of (1s,5r)-karahana ether and (1s,5r)-karahana lactone,the optically active forms of unique monoterpenes wit

(1$\text{S}$,5$\text{R}$)-(-)-Karahana ether (8,8-dimethyl-2-methylene-6-oxabi-cyclo[ 3.2.1]octane) and (1$\text{S}$,5$\text{R}$)-(-)-karahana lactone (8,8-dimethyl-2-methylene-6-oxabicyclo [3.2.1]octan-7-one) were synthesized from ($\text{S}$)-3-hydroxy-2,2-dimethylcyclo-hexanone. The natural karahana lactone was shown to be almost racemic ($\text{ca}$. 1.3 % e.e.).     

Methods for stereospecific synthesis of cis or trans hydrindanones

Methods are described for the stereospecific conversion of hydrindenone 3 either to the corresponding $\text{trans}$ fused or $\text{cis}$ fused hydrindanone (1 or 2, respectively.)     

A short synthesis of (s)-5-hydroxymethyl-(5h)-furan-2-one and derivatives from d-ribonolactone

We describe a short synthesis of ($\text{S}$)-5-hydroxymethyl-(5$\text{H}$-furan-2-one and some 5-O-derivatives, which are being used as key starting products for the synthesis of several antileukaemic lignan lactones, from $\text{D}$-ribonolactone.     

Stereocontrolled (E,Z and erythro, threo) synthesis of ⊙-hydroxyallylic sulphides

All four isomers of substituted 3-alkylthio-4-hydroxybutenes have been synthesised: both the geometry of the double bond and the relative stereochemistry of the two chiral centres are controlled.     

Enantiocontrolled synthesis of (S)-3-substituted cycloalkanones from (s)-2-(p-tolylsulfinyl)-2-cycloalkenones and diorganomagnesium reagents.

By appropriate choice of reaction conditions, the $\text{same}$ enantiomerically pure ($\text{S}$)-(+)-2-($\text{p}$-tolylsulfinyl)cycloalkenone can be converted into $\text{either}$ an ($\text{R}$)-or an ($\text{S}$)-3-substituted cycloalkanone in good to excellent enantiomeric purity.     

Empirical determination of medium effects on the equilibrium between transcis and transtrans 1,2-dibromo-4-t-butylcyclohexanes

Head space analysis, GLC retention time data, and solution calorimetry are used to determine the effect of medium on the thermodynamic parameters for the equilibrium (1) ? (2). It is shown that changes in ΔG° and ΔH° can be evaluated for the transfer of the equilibrium from a series of solvents to the gaseous phase which is used as the reference medium.     

(-)-β-Pinene as chiral promoter. Stereospecific access to (-)-γ-amino-β(r)-hydroxybutyric acid (gabob) and (r)-carnitine.2

The stereochemical correlation between the ene adducts 2 and 4a and their products of alkaline hydrolysis is reported. Starting from 2, by using a degradative sequence, a stereocontrolled approach to γ-amino-β($\text{R}$)-hydroxybutyric acid (GABOB) 8f and ($\text{R}$)-carnitine hydrochloride 8g is described.     

Cyclopropanation using rhodium (III) porphyrins : Large cis vs trans selectivity

Rhodium(III)tetraphenylporphyrin behaves as a sterically hindered cyclopropanation catalyst. Cis-cyclopropanes or “abnormal” products are obtained on reaction with cis-olefins or aromatics.     

Stereoselective synthesis of 1,8- and 1,5-diketo-trans-syn-trans-perhydroanthracenes

A stereOselective conversion of 1,8- and 1,5-diethoxy-9,10-anthraquinone to 1,8- and 1,5-diketo-$\text{trans}$-$\text{syn}$-$\text{trans}$-perhydroanthracenes by successive sodium borohydride, metal-ammonia, and catalytic reductions is described.     

Synthesis of the enantiomeric forms of cis and trans 1-benzyloxy-2,3-epoxy butane and of (3S,4S) 4-methyl-3-heptanol

The C₄erythro and threo diols (7) and (8) are converted either into the chiral epoxides (13) and (15) or into the enantiomers (14) and (16); the epoxide (13) is used as chiral synthon for the preparation of (3$\text{S}$,4$\text{S}$) 4-methyl-3-heptanol (21).     

Stereospecific synthesis of cis-2-alkenylcyclopropane carboxylic acids; A total synthesis of (±)-cis-chrysanthemic acid

A stereospecific route to $\text{cis}$-2,2-dimethyl-3-alkenyl-cyclopropanecarboxylic Acids is illustrated by a total synthesis of (±)-$\text{cis}$-Chrysanthemic Acid (11). The key step consists of an alicyclic Claisen rearrangement of $\text{O}$-silyl enolates derived from appropriately substituted ($\text{Z}$)-4-hexen-6-olides [e.g.(9)].     

[2+2] Cycloaddition of benzyne to cis,trans- and cis,cis-1,5-cyclooctadiene

The relative rates of formation of $\text{cis}$ and $\text{trans}$ [2+2]cycloadducts of benzyne to $\text{cis}$, $\text{trans}$- and $\text{cis}$, $\text{cis}$-1,5-cyclooctadiene, $\text{trans}$- and $\text{cis}$-cyclooctene are discussed and properties of the adducts (e.g., their unusual hydrogenation) are described.     

Stereospecific synthesis of trans-1,3-disubstituted-1,2,3,4-tetrahydro β-carbolines

The stereospecific synthesis of $\text{trans}$-1,3-disubstituted-1,2,3,4-tetrahydro β-carbolines has been accomplished in good yield by a two step sequence which involves Pictet-Spengler condensation of N_b-benzyltryptophan methyl ester with aldehydes, followed by removal of the 2-benzyl moiety from the corresponding tetrahydro β-carboline via catalytic hydrogenation.