Branched-chain carbohydrate lactones from a samarium(II) iodide-promoted serial deoxygenation-carbonyl addition reaction
摘要:
A new deoxygenation-carbonyl addition reaction mediated by samarium(II) iodide (SmI2) in THF/HMPA was examined with carbohydrate lactones and several substrates containing an alpha-alkoxy carboxylic ester. In a single reaction, these compounds were deoxygenated and subsequently coupled to several ketones by a carbonyl addition reaction. The first reactions studied simple ester and ketone adducts which were later elaborated to more complex optically active carbohydrate lactones appended to terpene ketones. Simple esters smoothly afforded beta-hydroxy carbonyl products. Fully benzoate-protected 3-deoxycarbohydrate lactones were reacted with simple ketones to produce C2-branched sugars. The attendant carbonyl addition to the least sterically hindered face of the aldonolactone provided the major products. Moderate diastereoselectivities (up to 5:1) were observed in the simple ketone products as determined by difference NOE studies. Finally, the terpene ketones, (-)-menthone or (+)-dihydrocarvone, were coupled to 3-deoxycarbohydrate lactones which gave C2-branched sugars with very high diastereoselectivities (up to 99:1).
Branched-chain carbohydrate lactones from a samarium(II) iodide-promoted serial deoxygenation-carbonyl addition reaction
摘要:
A new deoxygenation-carbonyl addition reaction mediated by samarium(II) iodide (SmI2) in THF/HMPA was examined with carbohydrate lactones and several substrates containing an alpha-alkoxy carboxylic ester. In a single reaction, these compounds were deoxygenated and subsequently coupled to several ketones by a carbonyl addition reaction. The first reactions studied simple ester and ketone adducts which were later elaborated to more complex optically active carbohydrate lactones appended to terpene ketones. Simple esters smoothly afforded beta-hydroxy carbonyl products. Fully benzoate-protected 3-deoxycarbohydrate lactones were reacted with simple ketones to produce C2-branched sugars. The attendant carbonyl addition to the least sterically hindered face of the aldonolactone provided the major products. Moderate diastereoselectivities (up to 5:1) were observed in the simple ketone products as determined by difference NOE studies. Finally, the terpene ketones, (-)-menthone or (+)-dihydrocarvone, were coupled to 3-deoxycarbohydrate lactones which gave C2-branched sugars with very high diastereoselectivities (up to 99:1).
Highly stereoselective couplings of carbohydrate lactones with terpene ketones promoted by SmI2
作者:Eric J. Enholm、Shujun Jiang
DOI:10.1016/s0040-4039(00)60008-4
日期:1992.10
Lactone 3-deoxycarbohydrates were reacted with samarium diiodide (SmI2) in THF/HMPA and the terpene ketones, (−)-menthone or (+)-dihydrocarvone; a serial reductive deoxygenation and an attendant carbonyl addition reaction afforded C2 branched sugars with high diastereoselectivities (up to 99:1).
Enholm, Eric J.; Jiang, Shujun, Heterocycles, 1992, vol. 34, # 12, p. 2247 - 2252
作者:Enholm, Eric J.、Jiang, Shujun
DOI:——
日期:——
Branched-chain carbohydrate lactones from a samarium(II) iodide-promoted serial deoxygenation-carbonyl addition reaction
作者:Eric J. Enholm、Shujun Jiang、Khalil Abboud
DOI:10.1021/jo00067a045
日期:1993.7
A new deoxygenation-carbonyl addition reaction mediated by samarium(II) iodide (SmI2) in THF/HMPA was examined with carbohydrate lactones and several substrates containing an alpha-alkoxy carboxylic ester. In a single reaction, these compounds were deoxygenated and subsequently coupled to several ketones by a carbonyl addition reaction. The first reactions studied simple ester and ketone adducts which were later elaborated to more complex optically active carbohydrate lactones appended to terpene ketones. Simple esters smoothly afforded beta-hydroxy carbonyl products. Fully benzoate-protected 3-deoxycarbohydrate lactones were reacted with simple ketones to produce C2-branched sugars. The attendant carbonyl addition to the least sterically hindered face of the aldonolactone provided the major products. Moderate diastereoselectivities (up to 5:1) were observed in the simple ketone products as determined by difference NOE studies. Finally, the terpene ketones, (-)-menthone or (+)-dihydrocarvone, were coupled to 3-deoxycarbohydrate lactones which gave C2-branched sugars with very high diastereoselectivities (up to 99:1).