Chemistry Reference
In-Depth Information
(16 mmol, 80%), mp 50-56
C. The product contained about 3% of the 5-thio-
methylmethyl ether, as estimated by
1
H NMR. Recrystallization from hexane at ca.
18
C gave material with mp 60-61
C, [a
D
]
214
(c
¼
¼
0.1, CHCl
3
).
O
O
O
O
DCC-DMSO
O
H
H
3
PO
4
pyridine
O
O
O
O
1870
80 %
Typical procedure. Cholan-24-al 1871 [1392]: Cholan-24-ol (1.033 g, 3 mmol) was
dissolved in dry benzene (10 mL) by gentle warming and dry dimethyl sulfoxide
(10 mL) was added, followed successively by dry pyridine (0.24 mL, 3.0 mmol),
distilled trifluoroacetic acid (0.12 mL, 1.5 mmol), and dicyclohexylcarbodiimide
(1.85 g, 9 mmol). The flask was tightly stoppered and left at room temperature for
18 h. Benzene (30 mL) was then added, and the crystalline dicyclohexylurea
formed was removed by filtration and washed with benzene. The combined filtrate
and washings were washed with water (3
50 mL), dried over sodium sulfate, and
concentrated under reduced pressure to give 2.12 g of a syrup, which partially
crystallized. The crude product was dissolved in benzene/hexane, 1:1, and chro-
matographed on 125 g of silica gel with this solvent mixture to give cholan-24-al
1871 (0.87 g, 84%); mp 102-104
C.
1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC)
An N-protected amino aldehyde can be prepared by Swern oxidation of an N-pro-
tected amino alcohol in the presence of an oxidizing agent comprising DMSO and
a water-soluble carbodiimide derivative as 1-ethyl-3-(3-dimethylaminopropyl)carbo-
diimide hydrochloride (EDC) in an organic solvent. The N-protected amino alcohol
can be derived from an l-, d-, or l-/d-amino acid, but usually is the N-protected-(S)-
a-amino alcohol derived from an N-protected l-amino acid.
DCC-DMSO
CHO
OH
TFA-pyridine
benzene
Cholan-24-ol
1871
84 %
EDC-DMSO
Boc
OH
Boc
CHO
H
H
TFA-pyridine
CH
2
Cl
2
Boc-L-Leucinol
1872
98 %
