Reaction of α, β-unsaturated sugar lactones with formaldoxime

Asymmetric 1,3-Dipolar Cycloaddition Reactions

“…Other cyclic and acyclic nitrones have been employed in reactions with 61, and in all cases, moderate to excellent endo:exo selectivities and excellent diastereofacial selectivities are obtained. 45 Three other research groups have been applying various γ-hydroxylated R,β-unsaturated carbonyl compounds in related reactions with nitrones; [78][79][80] however, the selectivities were somewhat lower than those obtained by Saito et al 45 Chiral allylic alcohols may also be cyclic, such as the sugar lactones used by Chmielewski et al [81][82][83] C-Methylnitrones 63 approach 64 in an endo-selective manner to the face of the alkene anti to the substituents of the lactone ring. In this reaction endo-65 is obtained as the sole product (eq 15).…”

2‐Fluoro‐1,3‐benzodithiole‐1,1,3,3‐tetraoxide: A Reagent for Nucleophilic Monofluoromethylation of Aldehydes

“…[1] The interest in fluoro-substituted osmundalactone 7 stems from the fact that osumundalactone is not only a biologically active natural product but also a useful reactive intermediate in organic synthesis, since it readily undergoes Michael addition, Baylis-Hillman reaction, 1,3-dipolar cycloaddition, and other olefinrelated reactions. [18] In addition, hydroxylated analogues 8 (R' = H) are widely useful synthetic intermediates for the preparation of various types of biologically attractive compounds ( Figure 2). [18] Consequently, compound 7 should become a sought-after building block in the synthesis of fluorinated isosteres of biologically relevant compounds derived form 6 or 8 because of the isosteric relationships between fluorine and hydrogen or the hydroxy group.…”

“…[18] In addition, hydroxylated analogues 8 (R' = H) are widely useful synthetic intermediates for the preparation of various types of biologically attractive compounds ( Figure 2). [18] Consequently, compound 7 should become a sought-after building block in the synthesis of fluorinated isosteres of biologically relevant compounds derived form 6 or 8 because of the isosteric relationships between fluorine and hydrogen or the hydroxy group. The approach to fluorinated isosteres of osmundalactone is shown in Scheme 6.…”

“…Treatment of crude 12 with dimethoxymethane in the presence of P 2 O 5 in CHCl 3 afforded anti-13 (46 %) and syn-13 (26 %), both of which should be attractive as building blocks for the synthesis of nonnatural fluorinated sugars and biologically active compounds. [18] In summary, we have developed a novel nucleophilic monofluoromethylating reagent, FBDT, which was shown to be suitable for the first nucleophilic monofluoromethylation of aldehydes based on the generation of an a-fluorocarbanion. Control of the selectivity of 1,2-versus 1,4-addition of FBDT to conjugated aldehydes was achieved by the choice of organic base.…”

Förster Resonance Energy Transfer-Based Fluorescent Probe for the Selective Imaging of Hydroxylamine in Living Cells

“…Initially, we endeavored to seek a highly selective HA-responsive site. Inspired by aza-Michael addition of HA to unsaturated system which could proceed rapidly at mild conditions, − we employed iminium ion as the strong electron withdrawing group and envisioned that the unsaturated system appended with iminium ion could serve as a novel HA-specific response site (Scheme A). On the other hand, benzopyrylium derivatives are a sort of excellent dyes due to their prominent optical properties including high fluorescence quantum yield and sufficient photostability. − By embedding the potential HA-specific response site into benzopyrylium dye, we fabricated a HA-responsive dye ( Chr ) with a long emission wavelength.…”