Chemistry Reference
In-Depth Information
4-Acetylsulfanyl-4-methyl-oxazolidine-2,5-dione 1189 was prepared with PCl
5
in
diethyl ether [863].
O
O
Me
SCOMe
PCl
5
N
O
O
OH
N
H
O
Me
S
O
COMe
1188
1189
N
2
,N
6
-Bis-benzyloxycarbonyl-l-lysine 1190 reacts with PCl
5
in dichloromethane on
heating from 0
C to reflux to give l-Lys(Z)-N-carboxy anhydride 1191 in 64-88%
yield [864-866].
N
H
NO
PCl
5
CH
2
Cl
2
, 0°C to reflux
Ph
O
h
O
COOH
O
1190
N
H
NO
h
O
O
O
O
1191
Similarly, (R)-4-benzylsulfanylmethyl-oxazolidine-2,5-dione was prepared from S-
benzyl-N-Cbz-l-cysteine and PCl
5
in diethyl ether [867], while (S)-3-(oxazolidine-
2,5-dion-4-yl)propionic acid esters were prepared from N-Bbzo-l-glutamic acid 5-
alkyl esters and PCl
5
[868].
NCAs of l-aspartic acid 4-benzyl ester, l-cysteine [869, 870], l-cystine [871, 872],
l-tyrosine [873], 4-nitrophenylalanine [874], 1-benzyl-histidine [875], 2,6-diamino-
heptanedioic monobenzyl ester [876], l-ornithine, and l-alanine [865] have been
prepared from the protected amino acids and PCl
5
.
A quantitative yield of l-alanine NCA was reported starting from the N-Boc-
protected amino acid and PCl
3
at 0
C in dichloromethane [862].
The preparation of 4-(3-pyridylmethyl)oxazolidine-2,5-dione 1194, the NCA of
b-pyridylalanine, is made di
cult by the presence of a pyridyl group in the amino
acid. The pyridyl group complicated attempts to phosgenate the amino acid, since
hydrogen chloride generated in the phosgenation reaction formed insoluble salts
with the amino acid and with any anhydride that may have formed [877].
The preparation of 4-(3-pyridylmethyl)oxazolidine-2,5-dione hydrochloride 1194
from the carbobenzoxy derivative 1193 was accomplished in 92% yield by treat-
ment with a solution of PCl
5
in dioxane [877].
