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13. Sto¨ckl, D.; Desagher, R.; Thienpont, L. M.; Debruyckere, G.; Vanpeteghem, C. H.
4.5.4. 17b-Methyl-20-oxo-18-nor-17a-pregna-5,13-diene-
Analyst 1994, 119, 2587–2590.
3b
,16
a,21-triyl 21-acetate 3,16-dibutyrate 15
14. Sto¨ckl, D.; Thienpont, L. M.; De Brabandere, V. I.; Deleenheer, A. P. J. Am. Soc.
Mass Spectrom. 1995, 6, 264–276.
Obtained from 16
a
,17 -epoxy-21-acetoxypregnenolone 13
a
15. De Brabandere, V. I.; Thienpont, L. M.; Sto¨ckl, D.; DeLeenheer, A. P. J. Lipid Res.
1997, 38, 780–789.
(97.1 mg, 0.25 mmol), under the above described reaction condi-
tions, in the presence of 10 mol % of Bi(OTf)3$xH2O and
(CH3CH2CH2CO)2O (0.41 mL, 2.5 mmol), after 2 h. The product was
purified by flash column chromatography on SiO2 using petroleum
ether 40–60 ꢀC/ethyl acetate 9:1 (v/v) and isolated as a white solid
in 77% yield (102 mg). Mp (MeCN): 115–117 ꢀC; TLC [petroleum
ether 40–60 ꢀC/ethyl acetate 4:1 (v/v)]: Rf¼0.52; IR 2959, 1732,
´
16. Schneider, G.; Hackler, L.; Sohar, P. Tetrahedron 1985, 41, 3377–3386.
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1232, 1180, 1023 cmꢁ1; 1H NMR (CDCl3, 600 MHz) see Table 4; 13
d C
NMR (CDCl3, 150.8 MHz)
455 (6), 439 (72), 351 (33), 249 (249), 103 (73), 89 (83), 80 (100).
d
see Table 4; EIMS m/z (%): 528 (28) Mþ,
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b-Methyl-20-oxo-18-nor-17a-pregna-5,13-diene-
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3
b,16a-diyl 3-acetate 16-formate 11
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To a solution of 16
(186.2 mg, 0.50 mmol) in HCO2Et (10 mL), Bi(OTf)3$xH2O
a,17a-epoxy-20-oxopregn-5-en-3b-yl acetate
1
(18.2 mg, 0.025 mmol) was added. The colour of the reaction mix-
ture gradually became dark purple. After 24 h under magnetic
stirring at reflux temperature, full conversion of the starting com-
pound was observed, as verified by TLC control [toluene/diethyl
ether 7:3 (v/v)]. The solvent was removed under reduced pressure,
and the resulting mixture was dissolved in diethyl ether (180 mL).
The organic phase was washed with 10% aq NaHCO3 (30 mL), water
(30 mL), dried with anhydrous Na2SO4 and concentrated under
reduced pressure to give a yellow solid. Purification by flash column
chromatography [petroleum ether 40–60 ꢀC/ethyl acetate 4:1 (v/v)]
afforded product 11 as a white solid (108 mg, 0.27 mmol, 54%). Mp
(n-hexane/acetone): 158–159 ꢀC; TLC [petroleum ether 40–60 ꢀC/
ethyl acetate 4:1 (v/v)]: Rf¼0.26; IR 2937, 1731, 1709, 1241, 1169,
1032 cmꢁ1; 1H NMR (CDCl3, 600 MHz) see Table 3; 13C NMR (CDCl3,
150.8 MHz) see Table 3; EIMS m/z (%): 400 (41) Mþ, 354 (66), 338
(100), 310 (56), 294 (95), 250 (71), 156 (78), 130 (73).
ˇˇ
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Acknowledgements
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R.M.A.P. thanks Fundaça˜o para a Ciencia e Tecnologia for a grant
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(SFRH/BD/18013/2004). J.A.R.S. thanks Universidade de Coimbra for
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Resonance Laboratory of the Coimbra Chemistry Centre
of the NMR data.
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Supplementary data
Supplementary data associated with this article can be found in
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