The synthesis of carbohydrate derivatives from acyclic precursors

Ager, David J.; East, Michael B.

doi:10.1016/s0040-4020(01)87942-4

Cited by 81 publications

(20 citation statements)

References 1,371 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Aspects of this subject have been surveyed in other reviews describing the synthetic utility of [4+ 2] and[4 + 3] cycloaddition reactions[1,25,119,122, 123]. The retro-Diels-Alder reactions of oxabicyclo[2.2.1] compounds under thermolytic conditions resulting in the extrusion of furan, acetylene or other stable species will not be covered, but the interested reader is directed to a recent review on this topic[ 122].…”

mentioning

confidence: 99%

Using ring-opening reactions of oxabicyclic compounds as a strategy in organic synthesis

Chiu

Lautens

1997

Topics in Current Chemistry

149

View full text Add to dashboard Cite

mentioning

confidence: 99%

Using ring-opening reactions of oxabicyclic compounds as a strategy in organic synthesis

Chiu

Lautens

1997

Topics in Current Chemistry

149

View full text Add to dashboard Cite

“…This chapter discusses the uses of these alkaloids as chiral ligands in asymmetric oxidation reactions. This steric effect is amplified in cyclic substrates [39,40]. The formation of an intermediate cyclic ester accounts for the cis-stereochemistry [21, 23-32] as reaction occurs on the least hindered face of the alkene [21,30,[33][34][35][36][37][38].…”

mentioning

confidence: 99%

“…The formation of an intermediate cyclic ester accounts for the cis-stereochemistry [21, 23-32] as reaction occurs on the least hindered face of the alkene [21,30,[33][34][35][36][37][38]. This steric effect is amplified in cyclic substrates [39,40]. The reaction conditions have to be carefully controlled to avoid oxidative cleavage of the diol product [28].…”

mentioning

confidence: 99%

See 1 more Smart Citation

Cinchona Alkaloids as Chiral Ligands in Asymmetric Oxidations

Ager¹

2009

Cinchona Alkaloids in Synthesis and Catalysis

Self Cite

View full text Add to dashboard Cite

For oxidation reactions, the cinchona alkaloids have been mainly employed to control the osmium-catalyzed conversion of an alkene to give a 1,2-diol or vicinal functionalized alcohol. As these are important asymmetric reactions, they have been the subject of a number of reviews [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. This chapter discusses the uses of these alkaloids as chiral ligands in asymmetric oxidation reactions. Oxidation reactions where an alkaloid is used in a phase-transfer sense are discussed in Chapter 5.The use of osmium tetroxide for the conversion of an alkene to a 1,2-diol is a wellestablished reaction [19][20][21][22]. The formation of an intermediate cyclic ester accounts for the cis-stereochemistry [21, 23-32] as reaction occurs on the least hindered face of the alkene [21,30,[33][34][35][36][37][38]. This steric effect is amplified in cyclic substrates [39,40]. The reaction conditions have to be carefully controlled to avoid oxidative cleavage of the diol product [28].There is a marked rate acceleration in the presence of a tertiary amine or pyridine [19,41]. This finding provided the background for the asymmetric dihydroxylation (AD) and, later, the asymmetric aminohydroxylation (AA) reactions as it is this ligand acceleration effect (LAE) that ensures the reaction pathway involving the ligand.The use of a cooxidant can reduce the amount of osmium required for a complete reaction of an alkene from stoichiometric to catalytic; some examples of oxidants that can achieve this are peroxides [20,22,35,37,[42][43][44] including hydrogen peroxide [20,42], chlorates [45], periodate [46,47], hypochlorite [48], N-methylmorpholine-N-oxide (NMMO) [22,34,35,37,49], potassium ferricyanide [50,51], and even air [52,53].Stereoselection for the OsO 4 reactions itself can also be observed when a directing group is adjacent to the alkene, such as in an allyl alcohol. An empirical rule has been devised, where the reagent approaches from the face opposite to the preexisting oxygen functionality. Although the hydroxy group may be protected, the presence of an acyl group reduces stereoselectivity. cis-Alkenes afford better selectivity

show abstract

“…These can be isolated in their pure forms. The cleavage of the oxa bridge of such systems leads to various functionalized disubstituted pyrrolidones with absolute control of the configuration of the different asymmetric centres (Ager & East, 1993).…”

mentioning

confidence: 99%