Synthesis of optically active 2-alkoxy-2H-pyran-3(6H)-ones. Their use as dienophiles in Diels-Alder cycloadditions
Optically active 2-alkoxy-2H-pyran-3(6H)-ones (4a-d) were synthesized in one step by the tin(IV) chloride-promoted glycosylation and rearrangement of the 2-acetoxy-3,4-di-O-acetyl-D-xylal (3) prepared from D-xylose (1). The absolute configuration of the new stereocenter at C-2 was determined by chem...
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todo:paper_00223263_v66_n26_p8859_IriarteCapaccio2023-10-03T14:31:24Z Synthesis of optically active 2-alkoxy-2H-pyran-3(6H)-ones. Their use as dienophiles in Diels-Alder cycloadditions Iriarte Capaccio, C.A. Varela, O. Epimerization Alkalinity Nuclear magnetic resonance Tin compounds Ytterbium Synthesis (chemical) 1,3 butadiene derivative carbohydrate pyran derivative pyranoside xylose ytterbium acetylation article chemical structure diastereoisomer enantiomer proton nuclear magnetic resonance stereochemistry synthesis Acetylation Cyclization Indicators and Reagents Magnetic Resonance Spectroscopy Pyrans Stereoisomerism Optically active 2-alkoxy-2H-pyran-3(6H)-ones (4a-d) were synthesized in one step by the tin(IV) chloride-promoted glycosylation and rearrangement of the 2-acetoxy-3,4-di-O-acetyl-D-xylal (3) prepared from D-xylose (1). The absolute configuration of the new stereocenter at C-2 was determined by chemical transformation of the dihydropyranones 4a and 4b into the known alkyl pentopyranosides (7a and 7b, respectively). Also, from 1H NMR experiments using a chiral ytterbium shift reagent, the enantiomeric excesses for 4a (> 86%) and 4b (>77%) were established. Enantiomerically pure 4c and 4d were obtained by reaction of 3 with chiral 2-octanol (R and S, respectively). Dihydropyranones 4a-d were employed as dienophiles in Diels-Alder cycloadditions with 2,3-dimethylbutadiene and butadiene. Under thermal conditions, only moderate yields (∼50%) of cycloadducts 9a-c and 10a were respectively obtained with good diastereofacial selectivity (> 80%). Optimized Lewis acid promoted cycloadditions led to 9a-d and 10a,c in higher yields (∼80%) and with higher diastereoselectivities (> 94%). The major products were formed by approach of the dienes from the less hindered face of the dihydropyranones, and the minor products (such as 11a) were formed by addition from the opposite side. Furthermore, cycloadduct 9a was stable in an alkaline solution, whereas 11a underwent epimerization under the same conditions. Fil:Iriarte Capaccio, C.A. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Varela, O. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_00223263_v66_n26_p8859_IriarteCapaccio |
| institution |
Universidad de Buenos Aires |
| institution_str |
I-28 |
| repository_str |
R-134 |
| collection |
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) |
| topic |
Epimerization Alkalinity Nuclear magnetic resonance Tin compounds Ytterbium Synthesis (chemical) 1,3 butadiene derivative carbohydrate pyran derivative pyranoside xylose ytterbium acetylation article chemical structure diastereoisomer enantiomer proton nuclear magnetic resonance stereochemistry synthesis Acetylation Cyclization Indicators and Reagents Magnetic Resonance Spectroscopy Pyrans Stereoisomerism |
| spellingShingle |
Epimerization Alkalinity Nuclear magnetic resonance Tin compounds Ytterbium Synthesis (chemical) 1,3 butadiene derivative carbohydrate pyran derivative pyranoside xylose ytterbium acetylation article chemical structure diastereoisomer enantiomer proton nuclear magnetic resonance stereochemistry synthesis Acetylation Cyclization Indicators and Reagents Magnetic Resonance Spectroscopy Pyrans Stereoisomerism Iriarte Capaccio, C.A. Varela, O. Synthesis of optically active 2-alkoxy-2H-pyran-3(6H)-ones. Their use as dienophiles in Diels-Alder cycloadditions |
| topic_facet |
Epimerization Alkalinity Nuclear magnetic resonance Tin compounds Ytterbium Synthesis (chemical) 1,3 butadiene derivative carbohydrate pyran derivative pyranoside xylose ytterbium acetylation article chemical structure diastereoisomer enantiomer proton nuclear magnetic resonance stereochemistry synthesis Acetylation Cyclization Indicators and Reagents Magnetic Resonance Spectroscopy Pyrans Stereoisomerism |
| description |
Optically active 2-alkoxy-2H-pyran-3(6H)-ones (4a-d) were synthesized in one step by the tin(IV) chloride-promoted glycosylation and rearrangement of the 2-acetoxy-3,4-di-O-acetyl-D-xylal (3) prepared from D-xylose (1). The absolute configuration of the new stereocenter at C-2 was determined by chemical transformation of the dihydropyranones 4a and 4b into the known alkyl pentopyranosides (7a and 7b, respectively). Also, from 1H NMR experiments using a chiral ytterbium shift reagent, the enantiomeric excesses for 4a (> 86%) and 4b (>77%) were established. Enantiomerically pure 4c and 4d were obtained by reaction of 3 with chiral 2-octanol (R and S, respectively). Dihydropyranones 4a-d were employed as dienophiles in Diels-Alder cycloadditions with 2,3-dimethylbutadiene and butadiene. Under thermal conditions, only moderate yields (∼50%) of cycloadducts 9a-c and 10a were respectively obtained with good diastereofacial selectivity (> 80%). Optimized Lewis acid promoted cycloadditions led to 9a-d and 10a,c in higher yields (∼80%) and with higher diastereoselectivities (> 94%). The major products were formed by approach of the dienes from the less hindered face of the dihydropyranones, and the minor products (such as 11a) were formed by addition from the opposite side. Furthermore, cycloadduct 9a was stable in an alkaline solution, whereas 11a underwent epimerization under the same conditions. |
| format |
JOUR |
| author |
Iriarte Capaccio, C.A. Varela, O. |
| author_facet |
Iriarte Capaccio, C.A. Varela, O. |
| author_sort |
Iriarte Capaccio, C.A. |
| title |
Synthesis of optically active 2-alkoxy-2H-pyran-3(6H)-ones. Their use as dienophiles in Diels-Alder cycloadditions |
| title_short |
Synthesis of optically active 2-alkoxy-2H-pyran-3(6H)-ones. Their use as dienophiles in Diels-Alder cycloadditions |
| title_full |
Synthesis of optically active 2-alkoxy-2H-pyran-3(6H)-ones. Their use as dienophiles in Diels-Alder cycloadditions |
| title_fullStr |
Synthesis of optically active 2-alkoxy-2H-pyran-3(6H)-ones. Their use as dienophiles in Diels-Alder cycloadditions |
| title_full_unstemmed |
Synthesis of optically active 2-alkoxy-2H-pyran-3(6H)-ones. Their use as dienophiles in Diels-Alder cycloadditions |
| title_sort |
synthesis of optically active 2-alkoxy-2h-pyran-3(6h)-ones. their use as dienophiles in diels-alder cycloadditions |
| url |
http://hdl.handle.net/20.500.12110/paper_00223263_v66_n26_p8859_IriarteCapaccio |
| work_keys_str_mv |
AT iriartecapaccioca synthesisofopticallyactive2alkoxy2hpyran36honestheiruseasdienophilesindielsaldercycloadditions AT varelao synthesisofopticallyactive2alkoxy2hpyran36honestheiruseasdienophilesindielsaldercycloadditions |
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1807324644680663040 |