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BOC protection of (S)-Alaninol; (S)-tert-butyl 1-hydroxypropan-2-ylcarbamate

SyntheticPage 614
DOI: 10.1039/SP614
Submitted Jul 11, 2013, published Jul 15, 2013
Nikola P. Chmel (N.Chmel@warwick.ac.uk), Pratik Gurnani (pratik.gurnani@warwick.ac.uk)
A contribution from Scott group, Warwick University


			Reaction Scheme: <img src="/images/empty.gif" alt="" />BOC protection of <span id="csm1374510582017" class="csm-chemical-name" title="(S)-Alaninol">(<em>S</em>)-Alaninol</span><img src="/images/empty.gif" alt="" />

Chemicals Used

(S)-Alaninol (Prepared in house, see page 292)
1M NaOH (aq)
BOC-anhydride (Fluka)
Dioxane (Fisher Scientific)

Procedure

(S)-Alaninol (2.0 g, 26.6 mmol) was dissolved in aqueous NaOH solution (50 ml, 1 M) and was cooled in an ice/water bath. A solution of di-tert-butyldicarbonate (6.5 g, 30.0 mmol) in dioxane (30 ml) was added and the mixture was stirred for 3 h. The mixture was then allowed to separate. The aqueous layer was acidified to pH ≈ 8 using a saturated NH4Cl solution and extracted with ethyl acetate (4 × 30 ml). The organic layer and ethyl acetate extracts were combined and the solvents were removed under reduced pressure. The obtained residue was extracted with ethyl acetate/hexane (1:2) mixture, filtered and the solvent were removed under reduced pressure. The obtained product was used in the subsequent step without further purification. Yield 3.3 g (71%).

Author's Comments

NMR was a little untidy but at this scale it was worth carry the product through to subsequent steps.

Data

1H NMR (400 MHz, 298 K, CDCl3) δH 4.78 (1H, s, NH), 3.73 (1H, s, CH), 3.59 (1H, dd, 3JHH = 10.8 Hz, 2JHH = 3.5 Hz, CH2), 3.47 (1H, dd, 3JHH = 10.8 Hz, 2JHH = 6.0 Hz, CH2), 3.06 (1H, s, OH), 1.42 (9H, s, tBu), 1.12 (3H, d, 3JHH = 6.8 Hz, CHCH3).

13C NMR (100 MHz, 298 K, CDCl3) δC 156.31 (C=O), 79.50 (C(CH3)3), 66.54 (CH2), 48.38 (CH), 28.40 (C(CH3)3), 17.33 (CHCH3).

MS (ESI+) m/z 198.2 ([M+Na]+)

MS (ESI-) m/z 174.8 ([M]-)

IR (cm-1) ν 3445, 3340, 2977, 2938, 2878, 1675, 1650, 1531, 1456, 1393, 1363, 1344, 1313, 1277, 1251, 1160, 1102, 1060, 1025, 934, 915, 880, 843, 781, 754.


Lead Reference

A. Benalil, B. Carboni and M. Vaultier, Tetrahedron, 1991, 47, 8177-8194. http://dx.doi.org/10.1016/S0040-4020(01)91013-0

Supplementary Information

1H NMR.jcamp
13C NMR.jcamp

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Keywords: addition, Alaninol, alcohols, amines, BOC anhydride, esters, protection

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