Chemistry Reference
In-Depth Information
Carbamates 531 of propynyl carbinols were prepared using phosgene and various
amines in toluene, in the presence of trimethylamine, without isolating the inter-
mediate chloroformate 530 [384].
H
N
O
Ph
O
Me
1.
COCl
2
, Py,
DMAP, 25 °C, 6h
2. (
_
)-
a
-FEA
OH
O
O
O
O
OC
OC
H
H
O
O
H
H
COOMe
COOMe
532
533
Optical resolution of alcohol 532, an intermediate in the total synthesis of gibberellic
acid, was effected through chromatographic separation of the derived diastereo-
meric carbamate 533, prepared from the corresponding alcohol 532 with phosgene
in the presence of pyridine, DMAP, and (
)-a-phenylethylamine at 25
C [385].
CH
2
OCH
2
Ph
"inversio
n
"
CH
2
OH
O
"substitution"
O
R
OCONHR
534
535
AcO
CH
2
CN
CH
2
OCH
2
Ph
"oxidation"
CH
2
OCH
2
Ph
AcO
CN
536
537
HO
COOH
HO
OH
538
CH
3
H
3
C
CH
3
R =
Using the carbamate meso compound 535, which is asymmetrically substituted
with a chiral moiety as an intermediate, prostaglandins 538 have been synthesized
[386].
