Tomasz Bauer

Stereochemical course of the [4+2] cycloaddition of 1-methoxybuta-1,3-diene to N-glyoxyloyl-(2R)-bornane-10,2-sultam. The formal synthesis of compactin and mevinolin

Abstract The chiral heterodienophile N -glyoxyloyl-(2 R )-bornane-10,2-sultam 2 , readily prepared from (2 R )-bornane-10,2-sultam 1 , was used in noncatalyzed atmospheric and high-pressure as well as in [Eu(fod) 3 ]-catalyzed [4+2] cycloadditions with 1-methoxybuta-1,3-diene 3 . All the [4+2] cycloadditions studied led to diastereoisomeric mixtures of 6-substituted derivatives of 2-methoxy-5,6-dihydro-2H-pyran 4–7 . The extent of asymmetric induction in these reactions was established by 1 H NMR analysis and the absolute configuration of the thermodynamically stable products 5 and 7 by X-ray analysis, and independently by chemical correlation. Stereochemical models for both noncatalyzed and [Eu(fod) 3 ]-promoted reactions are proposed. The [4+2] cycloadduct 5 was then effectively transformed into (4 R )-hydroxy-(6S)-hydroxymethyltetrahydropyrone-2 12 , a key synthon for the lactone moiety of compactin 10 and mevinolin 11 .

Highly enantioselective diethylzinc addition to aldehydes catalyzed by d-glucosamine derivatives

Abstract Synthesis of α-hydroxy sulfonamides derived from d -glucosamine and their application as ligands in the titanium tetraisopropoxide-promoted enantioselective addition of diethylzinc to benzaldehyde and selected aromatic and aliphatic aldehydes is presented. The reaction is highly enantioselective and enantiomeric excesses of up to 97% for benzaldehyde and 88% for n -hexanal were obtained.

Stereospecific synthesis of 5,6-dihydro-2H-pyran system. High-pressure cycloaddition of 1:2,3:4-di-0-isopropylidene- α-D-galactopyranose-6-ulose to 1-methoxybuta-1,3-diene

Abstract The high-pressure cycloaddition of 1:2,3:4-di-0-isopropylidene- α-D-galactopyranos-6-ulose (3) to 1-methoxybuta-1,3-diene (1) afforded diastereoisomerically pure cycloadduct 4 whose absolute configuration was determined.

Efficient synthesis of N-glyoxyloyl-(2R)-bornane-10,2-sultam

Abstract Starting from (2 R )-bornane-10,2-sultam 1 , the useful chiron N -glyoxyloyl-(2 R )-bornane-10,2-sultam 5 is prepared via its crystalline precursor 4 . The hemiacetal 4 whose structure was proved by the X-ray analysis is formed in diastereomerically pure form.

Asymmetric Morita–Baylis–Hillman reaction of chiral glyoxylates

Abstract The first Morita–Baylis–Hillman reaction of chiral glyoxylic acid derivatives, i.e. N -glyoxyloyl-(2 R )-bornane-10,2-sultam and (−)-8-phenylmenthyl glyoxylate is described. The reaction with cyclic α,β-unsaturated ketones proceeded under the catalytic influence of dimethyl sulfide in the presence of titanium tetrachloride. The adducts were obtained with very high diastereoisomeric excess (over 95% d.e.) and typical yields of 78%. The absolute configuration of the newly created stereogenic center was established by X-ray crystallographic analysis.

Stereochemistry of Diels-Alder reaction at high-pressure: influence of pressure on asymmetric induction in (4+2)cycloaddition of 1-methoxybuta-1,3-diene to 2,3-O-isopropylidene-D-glyceraldehyde

Abstract High-pressure (4+2)cycloaddition of 1-methoxybuta-1,3-diene ( 1 to 2,3-O-isopropylidene-D-glyceraldehyde ( 2 ) afforded four diastereoisomeric 6-substituted 2-methoxy-5,6-dihydro-2H-pyrans ( 3 ), for which the diastereoisomeric excess and absolute configuration were determined. The effects of pressure, temperature and solvent on asymmetric induction were examined. Stereochemical models were used for interpretation of the results.

Asymmetric [4+2] cycloaddition of cyclopentadiene to N′-tosylimine of N-glyoxyloyl-(2R)-bornane-10,2-sultam

Abstract The first synthesis of the N′-tosylimine of N-glyoxyloyl-(2R)-bornane-10,2-sultam using a modified Holmes method is described. The N′-tosylimine was used as a dienophile in the Lewis acid-catalyzed diastereoselective imino-Diels-Alder reaction with cyclopentadiene to give cycloadducts with good diastereoisomeric excess. The direction of the asymmetric induction depends on the Lewis acid used.

Highly stereoselective addition of 2-trimethylsilyloxyfuran to N-glyoxyloyl-(2R)-bornane-10,2-sultam

Abstract Eu(fod) 3 -catalyzed stereoselective nucleophilic addition of 2-trimethylsilyloxyfuran to N -glyoxyloyl-(2 R )-bornane-10,2-sultam yields g-substituted butenolides with high diastereoselectivity.

SYNTHESES OF DEOXYHEXOSES FROM DIASTEREOISOMERICALLY PURE HETERO-DIELS-ALDER ADDUCT

Abstract Syntheses of deoxyhexoses are presented. The concept is based on the functionalization of enantiomerically pure 6-hydroxymethyl-2-methoxy-5,6-dihydro-2H-pyran, which is easily synthesized by asymmetric hetero-Diels-Alder reaction. Methyl 4,6-dideoxy-α- d -arabino-hexopyranoside, methyl α- d -chalcoside and methyl α- d -desosanimide are synthesized.

The stereocontrolled synthesis of methyl 2,6-N,N-diacetyl-d-purpurosaminide C

Abstract Methyl 2,6-N,N- diacetyl- d -purpurosaminide 4 (methyl 2,6-diacetamido-2,3,4,6-tetradeoxy-α- d -erythrohexopyranoside) was synthesized from N -glyoxyloyl-(2 R )-bornane-10,2-sultam 2 and 1-methoxybuta-1,3-diene 3 in an 11-step reaction sequence with 6.5% of the overall yield.