Artur Jeżewski

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.

INTRAMOLECULAR DIELS-ALDER REACTION OF CHIRAL, HIGHLY OXYGENATED TRIENOATES DERIVED FROM SUGAR ALLYLTINS

Abstract The Lewis acid catalyzed intramolecular Diels-Alder reaction of sugar derived trienoates 3 led preferably to bicyclic endo-adducts 4 . The best stereoselectivity was observed for cyclization of the L-arabino-trienoate 3b , in which only one isomer (trans) was formed. High pressure (15 kbar) cycloaddition of 3a, 3b , and 3c , led to single stereoisomers 4a, 4b , and 4c in good yields. Conversion of adduct 4a to chiral cyclopentanes was described.

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.

The asymmetric ene reaction of N-glyoxyloyl-(2R)-bornane-10,2-sultam with 1-pentene and 1-hexene ☆

Abstract The asymmetric ene reaction of N -glyoxyloyl-(2 R )-bornane-10,2-sultam 2 and its hemiacetal 3 with 1-pentene 4 and 1-hexene 5 in the presence of Lewis acids is reported. All the ene reactions studied led to diastereoisomeric mixtures of olefins 6 and 7 or 8 and 9 , with predominance of products of the ( S ) absolute configuration on the newly formed stereogenic center. The absolute configuration ( via X-ray analysis of 6 and chemical correlation) and the extent of asymmetric induction were established. Stereochemical models are proposed.

The asymmetric cyclocondensation reaction of 1-methoxy-3-silyloxybuta-1,3-dienes with N-glyoxyloyl-(2R)-bornane-10,2-sultam

Abstract The asymmetric cyclocondensation reaction of 1-methoxy-3-trimethylsilyloxy- 3a, 1-methoxy-3-t-butyldimethylsilyloxy- 3b or 1-methoxy-3-triisopropylsilyloxybuta-1,3-diene 3c with N-glyoxyloyl-(2R)-bornane-10,2-sultam 2 in the presence of Eu(fod)3 is reported. For diene 3a the classic Danishefskys product 4 predominated over the desilylated [4+2] cycloadduct 5, whereas in the case of dienes 3b and 3c only product 4 and the primary [4+2] cycloadduct 6b or 6c were formed. The absolute configuration (via X-ray analysis of 5 and chemical correlation) and the extent of asymmetric induction were established.

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.