Reductive Cleavage of Tetrahydrofuryl Sulfur-Substituted Oxiranes:  Application to the Formal Synthesis of Kumausyne and Kumausallene

Abstract

[reactions: see text] Readily available sulfinyl and sulfonyl tetrahydrofuran methanol derivatives have been transformed efficiently into a variety of substituted tetrahydrofuryl alcohols by treatment with (PhSe)2 in the presence of an excess of NaBH4. Alternatively, oxirane cleavage with MgI2 produces the related ketones, amenable to stereocontrolled reduction. This reductive cleavage methodology has been applied to short formal syntheses of trans-Kumausyne and Kumausallene.

Sulfinate Allenyl Carbenoids: Synthesis of 2,5‐Dihydrofurans by Domino Rearrangement and Cyclization

“…In conclusion, we developed a new method for the synthesis of 2,5‐dihydrofurans containing a vinyl sulfone from propargylic sulfinate esters by treatment of catalytic silver fluoride. Such compounds have been prepared by other means and possess a promising, yet underdeveloped, chemistry . We need to determine what kind of sulfinate esters can be used in this process, explore the range of nucleophiles that can participate in the cyclization and the ring sizes that can be produced.…”

Highly Diastereoselective Katsuki−Jacobsen Oxidation−Epoxidation of α-Silyloxy Sulfinyl Dienes: Synthetic Applications

“…To test the usefulness of this process for obtaining densely functionalized tetrahydrofuran derivatives, we examined the nucleophilic epoxidation of 21 , which afforded a 93:7 mixture of sulfonyl oxiranes 31 in good yield (Scheme ) . Our recently described reductive cleavage of this moiety with freshly prepared MgI 2 gave cleanly the desired ketone 32 , thus opening a wide range of future synthetic applications.…”

Advances in Total Synthesis of Some 2,3,5‐Trisubstituted Tetrahydrofuran Natural Products

“…In continuation to their work on formal synthesis of (+)-kumausyne and (+)-kumausallene (see Scheme 6), [33] Pradilla and Castellanos [73] in 2007 reported a formal synthesis of trans-oxylipid (3 a) using KatsukiÀ Jacobsen oxidation-epoxidation of sulfinyl dienes (Scheme 26). Lithiation of 45 and addition to hexanal afforded separable dienols 174 a and 174 b, which could also be interconverted by Mitsunobu reaction.…”

“…A full account of similar chemistry involving reductive cleavage of tetrahydrofuryl sulfur-susbtituted oxirane was latter explored by Pradilla and co-workers in 2005 along with preliminary study in the use of MgI 2 , which however was not succesful for compound of type 48 (after OTBDPS conversion) in the reductive cleavage. [33] A formal synthesis of (À )-trans-kumausyne (1) was reported by Mereyala and co-workers [34] in 2000 from readily available diacetonide-D-glucose 53 (Scheme 7). In their synthesis 53 was converted into 3-deoxy-galactofuranose 54 following known procedure.…”