Synthesis of (−)‐Conduritol C (1L‐Cyclohex‐5‐ene‐1,2,3/4‐tetrol)

Synthesis of Both Enantiomers of Conduritol C Tetraacetate and of meso‐Conduritol D Tetraacetate by Oxidation of Benzoquinone Bis(ethylene acetal)

“…In contrast, reduction and acetylation of 11b resulted exclusively in diastereomer 12. Similar findings had previously been described by Vogel et al, [33] who also found a rather unselective reduction of 11a. By deduction from the X-ray data for compound 11a [24] we explain the reduction of 11a in terms of a preferential attack of the hydride nucleophile at the less hindered Si face of the enone to give 13 as the main product (Figure 3), whereas attack at the Re face to give 12 as the minor byproduct is still possible.…”

“…[6d, 33,40] Eluted next was crystalline 13 (119 mg, 54 %). 1 H and 13 C NMR data were identical to those published previously.…”

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

“…In the absence of substituents which have overwhelming steric effects, the dominant selectivity is influenced by the oxygen bridge, which steers the approach of reagents to the exo face of the substrate on the basis of steric considerations as well as by chelation. This selectivity applies to a wide variety of reactions on compounds with an olefinic bridge including osmylation [92,93], epoxidation [94], aziridination [95], hydrogenation [96], and hydroboration [97,98]. The [3 + 2] cycloaddition with C,Nodiphenylnitrone also generates the exo adduct [99], as did the Pauson-Khand reaction with acetylene [100].…”

“…Thus, the oxygen bridge in oxabicyclo[2.2.1]heptanone 177 was cleaved in the presence of triethylamine and TMSOTf to generate enone 178, which was an intermediate in the first total synthesis of (-)-conduritol C, Eq. 114 [93]. TBDMSOTf/triethylamine is also an effective combination for this transformation and has been used in the synthesis of myo-inositol derivatives, as well as (-)-conduritol B from 179, Eq.…”

On the Reactivity of (7-Oxabicyclo[2.2.1]hept-5-en-2-ylidene)amines. Different Reaction Paths Leading to the Same Final Products

“…Hydrolysis of 10 [11] followed by aromatization under workup of the reaction crude yields amide 7. Two aspects should be pointed out regarding the proposed reaction path: first, oxatrinorbornenone-derived ketals such as 11 have been found to be transformed into furan derivatives by treatment with fluorosulfonic acid (transformation of 11 into 12) [12] or Hg(NO 3 ) 2 in MeCN (transformation of 11 into 13) [13] [14] (Scheme 3) 4 ). Second, the alignment of the n(N) orbital with the s(C(1)ÀC(2)) bond (case of the (Z)-isomer of 5) is probably the reason for the ease of the fragmentation as predicted by Carrupt and Vogel [6].…”