Pyrans trimethylsilyl triflate

MMTS MsOH NBS NHMDS NMP NMR PPb Ph Pr PTC rt TBDMS Tf THF THP TLC TMEDA TMS TMSOTf Tol TOMAC Ts TsOH UDP methyl methylthiomethyl sulfoxide (=FAMSO) methanesulfonic acid N-bromosuccinimide sodium hexamethyldisililazide /V-methyl-2-pyrrolidone nuclear magnetic resonance parts per billion phenyl propyl Phase transfer catalysis room temperature t-butyldimethylsilyl triflatc (trifluoromethanesulfonate) tetrahydrofuran 2-tetrahydro-2//-pyran-2-yl thin-layer chromatography /V./V./V /V -tetramethylethylenediamine trimethylsilyl trimethylsilyl triflate p-tolyl trioctylmethylammonium chloride tosyl p-toluenesulfonic acid ultrasonically dispersed potassium... 

Trimethylsilyl triflate catalyses the condensation of enol silyl ethers (e.g., PhC(OSiMe3)=CHMe) with 2-acetoxytetrahydropyran to give a 62 38 mixture of erythroithreo pyrans (2).23 Cyclization of 7-hydroxyketones [such as (3)] (which are obtained by the action of dianions on epoxides) by bases gives on prolonged reaction the cis-tetrahydropyran (4) whilst shorter reaction times lead to a cis-trans mixture.21 ... 

Tedanolide 77 has showen EDso s of 250 pg/mL (vs. the KB human carcinoma cell line) and 16 pg/mL (v5. PS lymphocytic leukemia). 13-Deoxytedanolide 78 has shown a T/C of 189% at a dose of 125 pg/kg vs p388 cell lines. Many synthetic approaches have been demonstrated for the total synthesis of these two compounds. Jung and co-workers have developed a nonaldol aldol process in the synthesis of a Ci-Cn fragment. Treatment of the key intermediate 74 with trimethylsilyl triflate, followed by Still-Gennari olefmation conditions afforded the desired Ci-Cn (Z)-conjugated ester 75 in 80% yield as a 1 1 mixture with the pyran derivative 76. 

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