A. J. H. Klunder

A two-step chirality transfer from (−)-endo- to (−)-exo-tricyclo[5.2.1.026]deca-4,8-dien-3-one

Abstract An effective synthesis of enantiopure (−)-exo-tricyclo [5.2.1.02,6]deca-4,8-dien-3-one exo- 1 is realized starting from enantiopure (−)-endo- 1 applying Diels-Alder/retro-Diels-Alder methodology. The unusually high exo-stereoselectivity observed in the [4+2]-cycloaddition of (−)-endo- 1 with cyclopentadiene has been evaluated by semi-empirical AM1 transition state calculations.

Resolution of secondary alcohols by enzyme-catalyzed transesterification in alkyl carboxylates as the solvent.

Abstract The Porcine Pancreatic Lipase (PPL)- and Mucor Esterase-catalyzed resolution of 1-phenylethanol 5 in four different alkyl carboxylate solvents, viz. methyl acetate, propionate and butyrate and ethyl acetate, was evaluated. The beneficial influence of the addition of molecular sieves 4A to the reaction mixture is demonstrated. A Mucor Esterase-catalyzed resolution of 5 on a 0.5 mol scale is described. The kinetic resolution of a large variety of secondary alcohols ( 5 - 22b ) was investigated using both biocatalysts under the established optimal reaction conditions for substrate 5 .

PPL-catalyzed resolution of 1,2-and 1,3-diols in methyl propionate as solvent : an application of the tandem use of enzymes

Abstract The Porcine Pancreatic Lipase (PPL)-catalyzed transesterification of 1-phenyl-1,2-ethanediol 1, 2-phenyl-1,2-propanediol 2 1,2-decanediol 3 1,2-pentanediol 4 1,2-butanediol 5 1,2-propanediol 6 and 1,3-butanediol 7 in methyl propionate as solvent was evaluated. In alt substrates the primary hydroxy group is esterified exclusively. The enantioselectivity displayed in this PPL-catalyzed reaction is moderate. The enantiomeric excess of diol (-)-1 is enhanced by subjecting propionate (-)-8 with a moderate ee (obtained by a PPL-catalyzed esterification of racemic 1 in methylpropionate) to an enzyme-catalyzed hydrolysis (tandem principle).

Enzymic optical resolution and flash vacuum thermolysis in concert for the synthesis of optically active cyclopentenones

Abstract A practical synthesis of enantiomerically pure cyclopentenones with a predeterminated absolute configuration has been realized, starting from optically active tricyclo[5.2.1.02,6]decadienones.

Enzymic optical resolution and absolute configuration of tricyclo[5.2.1.02,6]decadienones

Abstract Access to optically active endo -tricyclodecadienones 1 (X=CH 2 ) has been realized by (i) classical resolution of the diastereomeric ephedrine salts of 3 and (ii) pig liver esterase catalyzed kinetic resolution of 2.

An efficient stereospecific total synthesis of (±) terrein

Flash vacuum pyrolysis of functionalized tricyclo|5.2.1.02,3|decenone epoxide 5, and acetals 3 and 4 affords cyclopentadienone epoxide 6 and acetals 10 and 8, respectively. These epoxides are suitable precursors for the synthesis of (±) terrein.

Stereospecific total synthesis of (±) pentenomycins by flash vacuum thermolysis of substituted tricyclo[5.2.1.02,6]decenones

The synthesis of 4-functionalized tricyclo[5.2.1.02,6]decenones 9, starting from furans, is described. These structures are shown to be suitable precursors for the synthesis of cyclopentenoids such as pentenomycin and analogs.

Stereospecific total synthesis of (−)-kjellmanianone and a revision of its absolute configuration

A fully stereocontrolled total synthesis of naturally occurring kjellmanianone 1 has been accomplished starting from tricyclo[5.2.1.02,6]decadienone 2-carboxylic ester 2. The key steps in this approach to 1 include Bartons halodecarboxylation methodology, nucleophilic epoxidation to introduce the hydroxy group and ultimately, a cycloreversion by using flash vacuum thermolysis. The R configuration of synthetic (−)-kjellmanianone was unequivocally established by an X-ray diffraction analysis of its precursor 6, implying that the previously assigned absolute configuration of (+)-kjellmanianone needs to be revised.

4-hydroxycyclopent-2-en-1-one and derivatives as chiral synthetic equivalents of cyclopentadienone in asymmetric diels-alder reactions

Abstract Endo-tricyclodecadienone 8a and related annelated cyclopentenones ( 8b, 20, 21a-c and 22 ) are synthesized in good ch

A stereo-and enantioselective approach to clavulones from tricyclodecadienone using flash vacuum thermolysis

Abstract The stereo- and enantioselective synthesis of clavulones 6 and their analogues 48 is described. γ-Hydroxycyclopentenones (−)- 13 and 44 , which are key intermediates in this approach, are obtained from enantiopure endo-tricyclo[5.2.1.02,6]decadienones (+)- 14 and (+)- 20 in 6 and 8 steps, respectively. Crucial steps are the reductive epoxy ring opening in compounds (+)- 25 and 39 to give the corresponding diols (+)- 27 and 40 , and the thermal cycloreversion of tricyclodecenones (+)- 27 and 41 , using the technique of flash vacuum thermolysis (FVT). The synthesis of enantiopure (−)- 13 represents a formal total synthesis of clavulones 6 . The synthesis of clavulone analogues (−)- 48E and (−)- 48Z (X = CH2OH) is completed by condensation of 44 with aldehyde 45 followed by elimination of water and removal of the protective THP-group.