Research Article
Received 31 May 2013,
Revised 09 July 2013,
Accepted 14 August 2013
Published online 24 October 2013 in Wiley Online Library
(wileyonlinelibrary.com) DOI: 10.1002/jlcr.3114
3
Synthesis of [3α- H] 17α-Hydroxy pregnenolone
3
and [3α- H] Pregnenolone
Yuan Tian, Yang Hong, Samuel J. Bonacorsi, Aaron Balog, and
Sharon Gonga
a
a
a
b
*
For the first time, [3α-3H] 17α-hydroxy pregnenolone (1) was synthesized through a multiple step sequence. The presence of
[3β-3H] isomer in RP-HPLC purified product was identified by tritium NMR. The [3β-3H] isomer was then separated from
[3α-3H] 17α-hydroxy pregnenolone with chiralPAK AD-H column. [3α-3H] pregnenolone (2) was synthesized from commercial
available 5-pregnen-3,20-dione in one step with an improved procedure.
Keywords: tritium; 17α-hydroxy pregnenolone; pregnenolone; isomer; tritium-NMR (T-NMR); chiralPAK AD-H column
3-methyl ether (3), a commercially available precursor via
Introduction
reduction of the 3-keto group (Scheme 1). Instead of the desired
[3-3H] product (1), a mixture of [20α-3H] 4-pregnen-17α,20beta-
Tritium-labeled 17α-hydroxy pregnenolone and pregnenolone
diol-3-one (6) and [20α-3H] 5-pregnen-17α,20 beta-diol-3-one
were required to support drug research and discovery at BMS.
Although [1,2-3H] or [21-3H] 17α-hydroxy pregnenolone and
(7) were isolated (Scheme 1). After RP-HPLC purification, the
(6)/(7) mixture showed a single peak with 99.7% RCP by RP-
HPLC. However, when the product was checked by T-NMR, it
[7-3H(N)] pregnenolone were commercially available, the cost of
the commercial products, in particular 17α-hydroxy pregnenolone,
was prohibitive for routine program use.
showed two peaks (ratio 60:40, Figures 3 and 4). Later, ChiralPAK
Several publications report syntheses of different versions of
AD-H HPLC analysis also revealed two peaks (ratio 26:74,
hydrogen isotope-labeled 17α-hydroxy pregnenolone and
Figure 5). After storage in 90% ethanol for 23 days, the product
was reanalyzed by ChiralPAK AD-H HPLC and showed a single
peak (98.5% RCP), which was identified as (6) by comparing it
pregnenolone. A.D.Tait1 reported a two-step synthesis of [3α-3H]
pregnenolone starting from unlabeled pregnenolone. In this instance,
a product with a specific radioactivity of 80 mCi/mmol was isolated
to 4-pregnene-17alpha,20 beta-diol-3-one authentic standard.
and purified by thin layer chromatography to 93% radiochemical
During the RP-HPLC purification, an early impurity was
purity (RCP). Marcel Gut2 reported the synthesis of [7α-3H] 17α-
hydroxy pregnenolone by debromination of a bromo analog of the
target compound. Martin I. Shapiro3 revealed evidence of a major
impurity existing in commercially available [7-3H] 17α-
hydroxypregnenolone. In addition, Weinman4 reported the synthesis
of [16-3H] 17α-hydroxypregnenolone. Deuterium-labeled 17α-
hydroxypregnenolone, such as [21-2H3] and [2,2,4,4,21,21,21-2H7]
17α-hydroxypregnenolone, was prepared, respectively, by
Muhammad Akhtar5 and C. Solleder.6,7 No publication was found
reporting the synthesis of [3α-3H] 17α-hydroxy pregnenolone.
However, George E. Joannou8 reported a multiple step procedure to
prepare unlabeled 17α-hydroxy pregnenolone.
collected and identified as [20β-3H] isomer by RP-HPLC and T-
NMR. The ratio of [20α-3H] isomer to [20β-3H] isomer in crude
product was 5.8:1.
Although the synthesis was unsuccessful, the results we
obtained provided interesting information on the conversion
from (7) to (6). The analytical methods we developed were useful
later for separation and characterization of the desired products.
Because we failed to obtain the desired product through the
initial route, we prepared an intermediate according to the
method reported by Geoge E. Joannou.8 Using the same
strategy, we successfully prepared (Scheme 2) [3α-3H] 17α-
hydroxy pregnenolone (1). The product was initially purified by
RP-HPLC and shown as a single peak in chromatogram; however,
the T-NMR analysis revealed the existence of [3β-3H] isomer of
In this paper, we report the synthesis of [3α-3H] 17α-hydroxy
pregnenolone (17.7 Ci/mmol) and [3α-3H] pregnenolone
(10.9 Ci/mmol) in high RCP and yield. The stereo chemical purity
of the compounds was further characterized by analyses of RP/
NP/ChiralPAK AD-H HPLC and T-NMR.
[3α-3H] 17α-hydroxy pregnenolone (1) (Figure 1) and [3α-3H]
pregnenolone (2) (Figure 2).
aRadiochemical Synthesis Group, Bristol–Myers Squibb Company, Route 206 and
Province Line Road, Princeton, NJ 08543, USA
bDiscovery Chemistry, Bristol–Myers Squibb Company, Route 206 and Province
Line Road, Princeton, NJ 08543, USA
Results and discussion
We initially attempted to synthesize [3α-3H] 17α-hydroxy
*Correspondence to: Yuan Tian, Radiochemical Synthesis Group, Bristol-Myers
Squibb Company, Route 206 and Province Line Road, Princeton, NJ 08543, USA.
E-mail: yuan.tian@BMS.com
pregnenolone (1) by utilizing 3,5-pregnadien-3,17-diol-20-one-
J. Label Compd. Radiopharm 2014, 57 1–11
Copyright © 2013 John Wiley & Sons, Ltd.