Question

what is the function of OTBMDS in these reactions?

Unfortunately the product 14, obtained in 56% yield as a single ner, resisted all attempts at removing the menthyloxy auxiliary ive 15. The successful outcomes reported in the literature for in related cases apparently all require the prior removal of the using the chiral shift reagent Eub of 17a e with the appropriate benz. lignanolactone derivatives 15a e in acceptable yields (66-78% with the wanted trans 8R/8'R configuration." For the unmasking of the 7' keto group via dithiane hydro several literature methods were tested, but in our experi R $ SS X 1 0 1 11 at 16 X = O(-) Menthyl Y YR 17 X=H 17 X = H 13a-d a R'-OM, RP-OTBMDS bR-R-Ome 11, 16, 17 CR-OTBMDS, RH dR-OTBMDS, ROMOSI R.R.O.CH-O 13a R'-OMe, R'EOTBMDS 13b R'-OTBMDS, R. H 13c R'-OTBMDS, ROMe 130 R-R-O CHO 15 a R'OM, RP-R-OTBMDS R=R? OMe, R-OTBMDS 15,18 CRI:OTBMDS, RRH R-OTBMDS, R-ROMe LR RP.R.R.O.CHO ime 2 Reagents and conditions: (1) #-BULI, THE DMPU. 12. - 78°C: (ii) (a) NaBH, KOH, ELOH 0°C, then st. (b) 0.1 NHC(pH 5-6); (iii) HMDS, THE, DMI, -78 °C to rt: (iv) (CF.COO), IPh, CH.CN H.O. It

Just want to know the function lf OTBMDS? It is assumingly a protecting group but for what?

Answer 1

Answer: To DMS - Tertiary butyl dimethyl silyl. • It is a protecting group for alcohols Coll.. It protects the –OH group from nucleophiles & соY N base . To protect a oH group we ure TB DMS- (1 and a base. • To de protect we use Ht, H₂O or F EBU g. R-4 Base - Sieme do Ro-si-Me I t-Bu -cut f Me t - Bu = tertiary butyl group R FOTBOMS