HYDROXYL GROUP PROTECTION BY PNB

MECHANISM

REACTION

wt/vol

MW

moles

density

equivs.

yield

I

0.091 g

386.71

0.0002

1.0

II

0.059 g

167.12

0.0004

1.5

III

0.064 g

206.33

0.0003

1.3

IV

0.007 g

122.17

0.0001

0.2

V

5.0 mL

VI

0.122 g

535.81

0.0002

(97%)

 

Procedure:  25 mL 1-neck flask, stirbar, septum, N2 inlet

Dissolved 0.059 g II, 0.064 g of DCC and 0.007 g of DMAP in 4.0 mL of dry CH2Cl2.  Stirred at rt.  Added a solution of 0.091 g of alcohol I in 1.0 mL of CH2Cl2.  Stirred for 45 min.  The reaction mixture was then concentrated by rotary evaporation to ~ 0.5 mL.  The product was isolated by flash chromatography on silica gel using 10:90 EtOAc-hexanes as eluant.  The product was a clear, colorless oil.

 

1H NMR (CDCl3, 300 MHz) d 8.29 (d, J = 8.4 Hz, ArH), 8.20 (d, J = 8.4 Hz, ArH), 5.97 (dd, J = 15.8, 5.1 Hz, H3), 5.86 (dt, J = 15.8, 5.5 Hz, H2), 5.58 (dq, J= 15.4, 6.2 Hz, H7), 5.41 (dd, J = 15.4, 7.0 Hz, H6), 4.86 (d, J = 5.5 Hz, H1), 3.95 (dd(apparent t), J = 5.9 Hz, H4), 3.85 (dd(apparent t), J = 6.6 Hz, H5), 1.68 (d, J = 6.2 Hz, H8), 0.87 (s, SiC(CH3)3), 0.85 (s, SiC(CH3)3), 0.02 (s, SiCH3), 0.00 (s, Si(CH )2), -0.01 (s, SiCH3).

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