Silyl Ethers - Thieme Chemistry

silyl ether) 64 undergoes selective scission with trifluoroacetic acid, giving alcohol 65 in
high yield (Scheme 32). [70] The more sterically hindered secondary silyl ether of 64 remains
unaffected by this reagent.
Scheme 32 Selective Cleavage of a tert-Butyldimethylsilyl Ether with Trifluoroacetic Acid [70]
MeO
MeO
MeO N
OMe
OMe
64
OTBDMS
OTBDMS
TFA, THF
H2O, 0 oC, 3 h
91%
MeO
MeO
MeO N
OMe
OMe
65
OTBDMS
Selectivity in the cleavage of tert-butyldimethylsilyl ethers can also be achieved with 10camphorsulfonic
acid. Thus, the secondary silyl ether but not the angular silyl ether of
compound 66 is removed with 10-camphorsulfonic acid in dichloromethane containing
a small amount of methanol to afford the diol 67 in excellent yield (Scheme 33). [71]
Scheme 33 Selective Cleavage of a tert-Butyldimethylsilyl Ether with
10-Camphorsulfonic Acid [71]
HO
H
O
OTBDMS
O
OTBDMS
FOR PERSONAL USE ONLY
394 Science of Synthesis 4.4 Silicon Compounds
CSA, CH2Cl2, MeOH, 25 oC, 1 h
100%
HO
66 67
H
O
OH
O
OTBDMS
Lankacidin C (63): [66]
A soln of bis(silyl ether) 62 (15 mg, 0.022 mmol) in a mixture of THF/HCO 2H/H 2O (6:3:1,
2.0 mL) was stirred at rt for 3 h. The mixture was cooled to 08C and neutralized with sat.
aq NaHCO 3 (2 mL). This mixture was poured into EtOAc (10 mL) and brine (10 mL). The
aqueous layer was extracted with EtOAc (10 mL). The combined organic layers were dried
(MgSO 4), filtered, and concentrated in vacuo. Purification by preparative TLC (EtOAc) gave
lankacidin C (63) as a white solid; yield: 8.7 mg (86%).
White, J. D.; Carter, R. G., SOS, (2002) 4, 371. 2002 Georg Thieme Verlag KG
OH