Use of the 2-Pyridinesulfonyloxy Leaving Group for the Fast Copper-Catalyzed Coupling Reaction at Secondary Alkyl Carbons with Grignard Reagents.

Investigation of the copper-catalyzed coupling reaction of 2-pyridinesulfonates with Grignard reagents revealed that reactions with catalytic Cu(OTf)2 were completed in <40 min. The results differed from those of the previous CuI-catalyzed reactions of tosylates in the presence of additives (LiOMe and TMEDA) for 12-24 h. It was shown that the preferred coordination of the leaving group to the reagents accelerated the reaction. Successful reagents were MeMgCl and other RMgX. Complete inversion was established.

Stereoselective synthesis of 17,18-epoxy derivative of EPA and stereoisomers of isoleukotoxin diol by ring opening of TMS-substituted epoxide with dimsyl sodium.

The reaction of TMS-substituted epoxy alcohols (and derivatives) with dimsyl sodium (NaDMSO) to give 1-alkene-3,4-diols was used for the synthesis of enantiomerically enriched 17(R),18(S)-EpETE and two diastereoisomers of isoleukotoxin diol. In the synthesis of 17(R),18(S)-EpETE, the α-ethoxyethyl ether (EE) of the epoxy alcohol derived from (R)-1-TMS-1-penten-3-ol underwent reaction with NaDMSO to give the mono EE-protected 1-hexene-3,4-diol. The aldehyde obtained by hydroboration/oxidation was subjected to Wittig reaction to afford a mono EE-protected diol. The corresponding mono mesylate was prepared and subjected to epoxide ring formation to afford 17(R),18(S)-EpETE stereoselectively. Similarly, a reaction of the anti epoxy alcohol derived from (R)-1-TMS-1-octen-3-ol with NaDMSO gave the anti form of 1-nonene-3,4-diol, which was converted to 12(S),13(R)-isoleukotoxin diol through Wittig reaction. 12(R),13(R)-Isoleukotoxin diol was synthesized in a similar manner.