Orally-effective, long-acting sorbitol dehydrogenase inhibitors: Synthesis, structure - Activity relationships, and in vivo evaluations of novel heterocycle-substituted piperazino-pyrimidines

J . Med. Chem. 2002, 45, 511-528

511

Or a lly-Effective, Lon g-Actin g Sor bitol Deh yd r ogen a se In h ibitor s: Syn th esis,

Str u ctu r e-Activity Rela tion sh ip s, a n d in Vivo Eva lu a tion s of Novel

Heter ocycle-Su bstitu ted P ip er a zin o-P yr im id in es

Margaret Y. Chu-Moyer,*^,†William E. Ballinger,^‡David A. Beebe,^§Richard Berger,^†,|J ames B. Coutcher,^§

Wesley W. Day, J iancheng Li,^†Banavara L. Mylari,^†Peter J . Oates,^§and R. Matthew Weekly^†,#

Departments of Cardiovascular and Metabolic Disease and Drug Metabolism Development, Pfizer Global Research and

Development, Groton Laboratories MS 8220-3095, Eastern Point Road, Groton, Connecticut 06340

Received September 19, 2001

Optimization of a previously disclosed sorbitol dehydrogenase inhibitor (SDI, II) for potency

and duration of action was achieved by replacing the metabolically labile N,N-dimethylsulfamoyl

group with a variety of heterocycles. Specifically, this effort led to a series of novel, in vitro

potent SDIs with longer serum half-lives and acceptable in vivo activity in acutely diabetic

rats (e.g., 62, 67, and 69). However, the desired in vivo potency in chronically diabetic rats,

ED₉₀e 5 mg/kg/day, was achieved only through further modification of the piperazine linker.

Several members of this family, including 86, showed better than the targeted potency with

ED₉₀values of 1-2 mg/kg/day. Compound 86 was further profiled and found to be a selective

inhibitor of sorbitol dehydrogenase, with excellent pharmacodynamic/pharmacokinetic proper-

ties, demonstrating normalization of sciatic nerve fructose in a chronically diabetic rat model

for ∼17 h, when administered orally at a single dose of 2 mg/kg/day.

In tr od u ction

Diabetes mellitus is a disease characterized by ab-

normal glucose metabolism. Diabetic patients are at risk

for developing long-term complications including neu-

F igu r e 1. Polyol pathway.

ropathy, nephropathy, retinopathy, and cardiovascular

disease.¹The clinical consequences of these complica-

tions include lower limb amputation, end-stage renal

failure, and loss of vision. The Diabetes Complications

and Control Study²and the United Kingdom Prospec-

tive Diabetes Study³demonstrated that strict and

sustained control of glucose excursions through inter-

ventions including intensive insulin therapy (HbA_1c

e

7%) reduces the risk of developing these complications

in type 1 and type 2 diabetics. However, relatively few

diabetics have adopted this strict, physician-monitored

regimen, and this type of round-the-clock control is not

practical for patients at large. At present, there is no

specific therapy available for diabetic complications. A

metabolic approach to control excess glucose flux in

diabetic tissues through the first step of the polyol

pathway (Figure 1) by aldose reductase inhibitors⁴has

shown promising results, particularly for diabetic neu-

ropathy, in both preclinical models and early clinical

trials.⁵An alternate, recent hypothesis proposes that

the redox changes caused by increased oxidation of

sorbitol to fructose in the second step of the pathway,

F igu r e 2. Prototype SDIs I and II and their heterocyclic

analogue III.

accompanied by a net imbalance of the reduced nicotin-

amide adenine dinucleotide to nicotinamide adenine

dinucleotide (NAD⁺) ratio, could be the underlying cause

of the vascular complications of diabetes.⁶

In chronically diabetic rats, a prototype sorbitol

7

dehydrogenase inhibitor (SDI), CP-166 572 (I, Figure

2) has been shown to prevent albumin leakage and

fructose accumulation in sciatic nerve as well as other

diabetic tissues, but seemingly contrary results have

been reported with regard to neural function,^8,9as has

already been iterated.¹⁰Because of the possibility that

these conflicting accounts may be a consequence of

differing experimental protocols used in the animal

models, as well as the pharmacokinetic/pharmaco-

dynamic issues with I, a weak and short-lived SDI,¹¹

initial efforts focused on potency improvements, which

led to the enantiomeric SDI II.¹⁰Although II is sub-

* Corresponding author. Tel: (860)441-5882. Fax: (860)715-9628.

E-mail: margaret_y_chu-moyer@groton.pfizer.com.

^†Department of Medicinal Chemistry.

^‡Current address: PGRD Pharmacokinetics, Dynamics, and Me-

tabolism, Groton, CT.

^§Department of Pharmacology.

^||Present address: Columbia University, Department of Chemistry,

New York, NY, 10027.

Current address: PGRD Clinical Safety and Risk Management,

La J olla, CA.

#

Current address: PGRD Chemical Research and Development,

Groton, CT.

Published on Web 12/20/2001

512 J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 2

Chu-Moyer et al.

Sch em e 1^a

stantially more potent than I in vitro, it still retains the

metabolically labile N,N-dimethylsulfamoyl moiety.

Therefore, a program to identify potent, orally active

SDIs with longer serum half-lives was initiated, with

the objective of providing better tools to probe the

biological consequences of blocking the second step of

the polyol pathway. The immediate medicinal chemistry

strategy became the replacement of the sulfamoyl

moiety with a more metabolically stable heterocyclic

group.

Ch em istr y

Starting with the activated pyrimidines 1a -d (X )

Cl,¹²OMs,¹³OSO₂[2,4,6-triisopropyl]Ph, and OTf, re-

spectively), the target compounds 14-33 were for the

most part prepared using two methods, differing pri-

marily in order of addition (Scheme 1). The first ap-

proach proceeds with the reaction of 1a -c with substi-

tuted piperazines 2a -j¹⁴to provide compounds 3a -k .

Removal of the methyl ether protecting group under

standard conditions afforded the target compounds.

Alternatively, mesylate 1b may be first reacted with

piperazine (4) to provide piperazino-pyrimidine 5. Sub-

sequent reaction with heterocyclic chlorides 6a -f¹⁴

afforded compounds 7a -h that are deprotected as

before to give the target compounds.¹⁵When the highly

reactive trifluoromethylsulfonylpyrimidine 1d was re-

acted with piperazine (4), the N,N′-bis-substituted

intermediate 8 (R¹) 2-methoxymethyl-pyrimidin-4-yl)

was obtained, which upon deprotection gave compound

22. Finally, one compound in this series was synthesized

via the reaction of chloropyrimidine 1a with Boc-

piperazine (9) followed by deprotection of the methyl

ether (Me₂BBr) and Boc group (HCl) to provide the

amino alcohol bis(HCl) salt 12. Subsequent reaction

with 4-chloro-2,6-dimethyl-pyrimidine (13) gave the

desired target compound. This latter method provides

a late-stage common intermediate (e.g., 12) from which

analogues can be produced in one step.

Synthesis of analogues bearing the R-(+)-hydroxy-

ethyl side chain at the pyrimidine 2-position, compounds

50-62 and 65-71, follows similarly (Scheme 2). For

example, reaction of the activated pyrimidines 34a -c

(R ) Ac and X ) Cl or OMs, R ) butyryl and X ) Cl,

respectively)¹³with R¹-substituted piperazines 2g-j and

35a -j¹⁴provides compounds 36a -o, which are hydro-

lyzed under basic conditions to provide the target

compounds.¹⁶Alternatively, the reaction of mesylate

34b with piperazine (4) provides piperazino-pyrimidine

37a , which upon reaction with activated heterocyclic

chlorides 6c,e, 13, and 38 gives the penultimate precur-

sors 39a -d . Deprotection of the acetate protecting

group as before provides the target compounds. Reaction

of two equivalents of chlorobutyrate 34c with piperazine

(4) cleanly gave the N,N′-bis-substituted intermediate

40 (R¹) (R)-2-(1-butyrloxyethyl)-pyrimidin-4-yl), which

was bis-deprotected under the standard conditions to

provide the target compound. Again, one target com-

pound in this series was synthesized via the reaction of

piperazino-pyrimidine 37b (obtained by the hydrolysis

of acetate ester 37a ) with quinoxaline chloride 41,

exemplifying a method that would allow a one-step

synthesis of analogues from a common intermediate.

For those analogues with R¹) 4,6-disubstituted-

pyrimidin-2-yl, the requisite substituted piperazines

a

Reagents and conditions: (a) Et₃N or i-Pr₂NEt, THF or DME

or i-PrOH, reflux [general procedure A]. (b) THF, reflux. (c) Et₃N

or i-Pr₂NEt, CH₂Cl₂or THF or i-PrOH or n-BuOH, -78 °C f

reflux [general procedure B]. (d) H₂(50 psi), 10% Pd/C, NaOAc,

EtOH [general procedure C]. (e) (From 1d ), CH₂Cl₂, room tem-

perature. (f) (From 1a ), Et₃N, THF, reflux. (g) Me₂BBr, Et₃N,

CH₂Cl₂, 0 °C f room temperature. (h) 4 N HCl, dioxane, room

temperature. (i) i-Pr₂NEt, n-BuOH, reflux. (j) BBr₃, CH₂Cl₂, 0 °C

f room temperature or Me₂BBr, Et₃N, CH₂Cl₂, 0 °C f room

temperature [general procedure D].

35a -d were synthesized following the route shown in

Scheme 3. The reaction of 1-benzylpiperazine (42) with

N,N′-bis(tert-butoxycarbonyl)thiourea (43) in the pres-

ence of HgCl₂provided bis(Boc)-protected guanidine 44

that was deprotected with trifluoroacetic acid (TFA) to

give the guanidinium trifluoroacetate salt 45.²⁰The

reaction of 45 with diketones 46a -d ¹⁴in a refluxing

solution of i-PrONa/i-PrOH gave the desired 4,6-disub-

stituted-pyrimidino-piperazines.¹⁸Removal of the benzyl

group under transfer hydrogenolysis conditions provided

compounds 35a -d . As this methodology proved useful

in preparing analogues of this type, a more convergent

route was also realized by replacing the benzyl group

with the (R)-2-(1-acetoxy)-pyrimidin-4-yl group such

that the final target compounds 63 and 64 were directly

obtained after the reaction with the diketone 46e or

Sorbitol Dehydrogenase Inhibitors

J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 2 513

Sch em e 2^a

Sch em e 3^a

a

Reagents and conditions: (a) Et₃N, HgCl₂, DMF, 0 °C f room

temperature [general procedure H]. (b) TFA/CH₂Cl₂, room tem-

perature [general procedure I]. (c) i-PrONa/i-PrOH, reflux [general

procedure J ]. (d) 10% Pd/C, HCO₂NH₄, MeOH, reflux [general

procedure K].

in ∼80-90% ee for a <10 g scale in a continuum to

complete racemization for a >100 g scale. Thus, on a

large scale, the synthesis of 73a was more conveniently

performed using the more reactive triflate¹³34d with

cis-dimethylpiperazine 72a at 80 °C, routinely providing

compound 73a in 80-90% ee. Separation of the enan-

tiomers by chiral high-performance liquid chromatog-

raphy (HPLC) was easily accomplished to provide the

desired (R)-enantiomer in >98% ee.²²Removal of the

benzyl protecting group was accomplished under trans-

fer hydrogenolysis conditions following in situ formation

of the HCl salt of 73a -c to give the free amines 74a -

c. Reaction of 74a -c with activated heterocycles 34c

and 75a -c under standard conditions provided the

butyrate-protected penultimate precursors 76a -h . Re-

moval of the ester protecting group was accomplished

in general with LiOH, although in some instances

K₂CO₃or HCl was used. In the event that deprotection

of a heterocyclic head piece containing a methyl ether

was necessary, treatment with BBr₃effected both meth-

yl ether and concomitant butyrate cleavage to give the

target compounds.

For those analogues where the methyl group(s) is/are

distal to the chiral pyrimidine, several related routes

were used depending on the methyl substitution pat-

tern. First, 2,6-cis-dimethylpiperazine (77) was con-

densed with chloropyrimidine 34c, selectively on the

less-hindered nitrogen, providing compound 78. Deriva-

tization of pyrimidino-piperazine 78 and benzyl-piper-

azine 72c with the 4-methoxymethyl-6-methyl-pyrimi-

din-2-yl group follows that procedure previously de-

scribed in Scheme 3, i.e., construction of the heterocycle

via reaction with bis(Boc)-thiourea 43 followed by Boc

a

Reagents and conditions: (a) Et₃N, THF or i-PrOH, room

temperature f reflux [general procedure E]. (b) (From 34b), THF,

reflux. (c) Et₃N or i-Pr₂NEt, i-PrOH or n-BuOH, room temperature

f reflux [general procedure F]. (d) (From 34c), Et₃N, i-PrOH,

reflux. (e) LiOH‚H₂O, 3:1:1 THF/MeOH/H₂O, room temperature.

(f) Et₃N, i-PrOH, reflux. (g) LiOH‚H₂O, THF/MeOH/H₂O, 0 °C f

room temperature or K₂CO₃, MeOH, room temperature [general

procedure G].

dicarbonyl equivalent 46f (see 37a f 48 f 49 f 63 and

64).

The synthesis of analogues containing mono- or

dimethyl-substituted piperazine linkers is based es-

sentially on the chemistry shown for the unsubstituted

piperazine linker derivatives above (Scheme 4). How-

ever, the reaction sequence and conditions are dictated

by the availability and reactivity of the differentially

protected piperazines 72a -c (R²) R⁶) â-Me,¹⁹R²)

R-Me,²⁰and R²) â -Me,²⁰respectively).²¹Furthermore,

the substituted piperazines may be linked to the chiral

pyrimidine with the methyl group(s) proximal to or

distal to said chiral pyrimidine. As a consequence of

these considerations, three major routes were used in

the preparation of analogues 85-97.

For those compounds with the piperazine methyl

group(s) proximal (positions R²and R⁶) to the chiral

pyrimidine, the protected piperazines 72a -c were

condensed with the chloropyrimidine 34c in the first

step to give compounds 73a -c, with more forcing

conditions required in the case of cis-dimethylpiperazine

72a (neat, 155 °C) as compared with the monomethyl

piperazines 72b,c (n-butanol, reflux). In the former case,

scale-dependent epimerization was observed resulting

514 J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 2

Chu-Moyer et al.

Sch em e 4^a,b

a

b

Reagents and conditions. Compounds containing the descriptors R², R³, R⁵, and R⁶are hydrogen unless otherwise specified. (a)

(From 34c and 72a ), 155 °C, neat; (from 34d and 72a ), Et₃N, CH₃CN, reflux; (from 34d and 72b,c), i-Pr₂NEt, n-BuOH, reflux. (b) HCl,

MeOH then 10% Pd/C, HCO₂NH₄, MeOH, reflux [general procedure L]. (c) Et₃N or i-Pr₂NEt, i-PrOH or n-BuOH, reflux or 130 °C, neat

[general procedure M]. (d) THF, reflux. (e) Et₃N, HgCl₂, DMF, 0 °C f room temperature [general procedure H]. (f) TFA/CH₂Cl₂, room

temperature [general procedure I]. (g) i-PrONa/i-PrOH, reflux [general procedure J ]. (h) HCl, MeOH then 10% Pd/C, HCO₂NH₄, MeOH,

reflux. (i) 34c, Et₃N, i-PrOH, reflux [general procedure N]. (j) ACE-Cl, NaI, acetone, room temperature then MeOH, reflux. (k) LiOH,

THF/MeOH/H₂O, room temperature or K₂CO₃, MeOH, room temperature or HCl, MeOH, room temperature or BBr₃, CH₂Cl₂, 0 °C f

room temperature [general procedure O].

deprotection and condensation with diketone 46d to give

81a ,b. The benzyl-substituted analogue 81b was depro-

tected under transfer hydrogenolysis conditions and the

chiral pyrimidine was appended to give compound 81d .

The thusly synthesized precursors 81a ,d were each

simultaneously demethylated and de-esterified with

BBr₃to give the target compounds.

Finally, monomethyl benzyl piperazine 72b was re-

acted with activated heterocycles 75a -c, debenzylated

under standard transfer hydrogenolysis conditions or

using the ACE-Cl/NaI method of Buchwald,²³and

condensed with chloropyrimidine 34c as before to

provide penultimate precursors 84a -c, which were

deprotected to give the target compounds.

to the first-line in vivo screen measuring the prevention

of sciatic nerve fructose accumulation (acute model) in

streptozocin (STZ)-induced diabetic rats. Test com-

pounds were dosed 4, 7, and 24 h post STZ treatment,

and for select compounds, ED₅₀values were generated

(represented as mg/kg/day, total dose) to determine

which compounds were sufficiently robust enough for

further characterization. Those compounds with acute

in vivo ED₅₀e 1 mg/kg/day were then advanced to the

secondary in vivo screen where compounds were tested

for their ability to normalize (ED₉₀) elevated sciatic

nerve fructose in a reversal protocol (chronic model)

rather than a prevention protocol. In this more relevant

model, rats were made diabetic (STZ) for 1 week, and

on day 8, compound dosing was initiated and continued

once a day for 5 days.

Biology

Primary in vitro data were initially generated using

commercially available sheep liver sorbitol dehydro-

genase (s-SDH) and then changed over to recombinant

human sorbitol dehydrogenase (h-SDH) as it became

available.^24,25Compounds of interest were progressed

Str u ctu r e-Activity Rela tion sh ip s

Initial substitution of the N,N-dimethylsulfamoyl

moiety of I with phenyl or simple heterocycles such as

pyridine, pyrimidine, pyrazine, and triazine (e.g., 14-

Sorbitol Dehydrogenase Inhibitors

J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 2 515

Ta ble 1. Structure-Activity Relationships for Compounds 14-33: Heterocyclic Analogues of CP-166 572 (I)

s-SDH IC₅₀

(µM) ( se (n)

h-SDH IC₅₀

(µM) ( se (n ) 3)

compd no.

R¹

mp (°C)

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

phenyl

131-133

139-141

164-166

185-186.5

9.4 (1)

3.0 (1)

1.1 ( 0.2 (2)

2.3 (1)

1.3 (1)

2.6 (1)

0.35 ( 0.05 (2)

0.48 (1)

1.1 (1)

0.49 (1)

6.5 (1)

4.8 (1)

3.2 (1)

0.74 ( 0.04 (2)

3.2 (1)

pyridin-2-yl

pyrimidin-2-yl

pyrimidin-4-yl

pyrazin-2-yl

[1,3,5]triazin-2-yl

195-196.5

175-176

171.5-173.5

237-239

250-255

235-237

124-126

192-193

200-201.5

278-281

134-136

139-141.5

144-145

172-174

207.5-209

4,6-dimethyl-pyrimidin-2-yl

2,6-dimethyl-pyrimidin-4-yl

2-hydroxymethyl-pyrimidin-4-yl

4,6-dichloro-[1,3,5]triazin-2-yl

1H-benzimidazol-2-yl

1-ethyl-1H-benzimidazol-2-yl

benzothiazol-2-yl

0.093 ( 0.025

0.14 ( 0.04

0.26 ( 0.13

benzoxazol-2-yl

0.19 ( 0.04

benzo[d]isothiazol-3-yl S,S-dioxide

benzo[d]isothiazol-3-yl

benzo[d]isoxazol-3-yl

isoquinolin-1-yl

quinolin-2-yl

quinazolin-4-yl

0.33 ( 0 (2)

0.41 ( 0.07 (2)

0.43 (1)

0.59 (1)

0.89 (1)

0.064 ( 0.004

0.12 ( 0.02

0.15 ( 0.03

0.087 ( 0.009

CP-166 572 (I)

0.24 ( 0.01

Ta ble 2. Structure-Activity Relationships for Compounds 50-57: Effect of the (R)-Hydroxyethyl Group at the Pyrimidine 2-Position

h-SDH IC₅₀

(µM) ( se (n ) 3)

acute in vivo ED₅₀

(mg/kg/day)

compd no.

R¹

mp (°C)

50

51

52

53

54

55

56

57

4,6-dimethyl-pyrimidin-2-yl

2,6-dimethy-pyrimidin-4-yl

(R)-2-hydroxyethyl-pyrimidin-4-yl

benzoxazol-2-yl

benzo[d]isothiazol-3-yl

benzo[d]isoxazol-3-yl

isoquinolin-1-yl

132-133

125.5-127

158-160

139-141

0.023 ( 0.003

0.031 ( 0.003

0.040 ( 0.001

0.035 ( 0.004

0.012 ( 0.003

0.037 ( 0.015

0.034 ( 0.002

0.044 ( 0.005

1.3

5

1.0

12

129-131

quinolin-2-yl

19) provided modestly active compounds, with IC₅₀

values vs s-SDH in the low micromolar range (Table 1).

The addition of hydrophobic substituents such as methyl

and chloro to the pyrimidine and triazine core hetero-

cycles, respectively, increased activity by ∼3-5× (e.g.,

20, 21, and 23). Because hydrophobic groups appeared

to be beneficial for binding to the enzyme, a series of

fused heterocycles was also surveyed. In general, the

less polar heterocycles such as benzoxazole 27, benzo-

[d]isothiazole 29, benzo[d]isoxazole 30, isoquinoline 31,

quinoline 32, and quinazoline 33 were favored over the

more polar benzimidazoles 24 and 25 and benzo[d]-

isothiazole S,S-dioxide 29. The intrinsic potency of these

fused bicyclic heterocycles was comparable to the sub-

stituted monocyclic heterocycles.

On the basis of concurrent structure-activity rela-

tionships (SAR) investigations that showed the impor-

tance of the enantiomeric 2-hydroxyethylpyrimidine

core,¹⁰select compounds from the heterocycle series

were synthesized, which incorporated that side chain

(Table 2). In vitro testing against h-SDH for these

derivatives and their related hydroxymethyl congeners²⁶

showed that in vitro activity generally increased ∼3-

7-fold after the incorporation of the (R)-hydroxyethyl

side chain. Preliminary in vivo analysis of compounds

50-53 showed reasonable activity in the acute model

with ED₅₀values ranging from 1 to 12 mg/kg/day.

With the above results in hand, further optimization

of the heterocycle was pursued (Table 3). Exploration

of the 4,6-dimethylpyrimidine in 50 showed that this

substitution pattern was optimal vs having just one

methyl substituent (58) or increasing the size of the

alkyl groups to CF₃, ethyl, or isopropyl (59-61). Incor-

poration of an aromatic substituent (63 and 64) was also

less well-tolerated. Pharmacokinetic analysis of 50 (data

not shown) revealed the metabolite 62, where one of the

methyl substituents in 50 was oxidized to a hydroxy-

methyl group. The in vitro IC₅₀and in vivo acute ED₅₀

of 62 were very similar to that of 50. SAR around the

benzoxazole derivative 53 revealed that the oxazolo-

pyridines 65-68 were reasonable replacement ana-

logues, with the latter two having equivalent in vitro

potency with the parent benzoxazole. More interesting,

however, was an ∼20× increase in the in vivo acute

assay for the oxazolopyridines 67 and 68 vs the benz-

oxazole 53. Quinoxaline-substituted derivatives 69-71

516 J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 2

Chu-Moyer et al.

Ta ble 3. Structure-Activity Relationships for Compounds 58-71: Refinement of the Heterocyclic Head-Piece

acute

chronic

h-SDH IC₅₀

(µM) ( se (n ) 3)

in vivo ED₅₀

(mg/kg/day)

in vivo ED₉₀

(mg/kg/day)

compd no.

R¹

mp (°C)

58

59

60

61

62

63

64

65

66

67

68

69

70

71

4-methyl-pyrimidin-2-yl

116-117.5

156.5-158

104-105

82-83.5

0.11 ( 0.04

4,6-bis-trifluoromethyl-pyrimidin-2-yl

4,6-diethyl-pyrimidin-2-yl

4,6-diisopropyl-pyrimidin-2-yl

4-hydroxymethyl-6-methylpyrimidin-2-yl

4-methyl-6-phenyl-pyrimidin-2-yl

4-phenyl-pyrimidin-2-yl

oxazolo[4,5-b]pyridin-2-yl

oxazolo[4,5-c]pyridin-2-yl

oxazolo[5,4-c]pyridin-2-yl

oxazolo[5,4-b]pyridin-2-yl

quinoxalin-2-yl

0.19 ( 0.06

0.080 ( 0.010

0.072 (0.013

0.020 ( 0.003

0.22 ( 0.10

0.067 ( 0.010

0.17 ( 0.03

0.080 ( 0.017

0.024 ( 0.002

0.032 ( 0.005

0.036 ( 0.012

0.008 ( 0.001

0.12 ( 0.04

139-140

0.5

190-191.5

178-180

181-183

153-156

106-108

145-147

143-145

0.5

1.0

10

>20

3-methyl-quinoxalin-2-yl

6,7-dichloro-quinoxalin-2-yl

azine congeners were synthesized in almost all different

combinations while retaining the four heterocycle groups

that were previously shown to give good in vitro

potency: 4-hydroxymethyl-6-methylpyrimidin-2-yl, (R)-

2-hydroxyethyl-pyrimidin-4-yl, 4-oxazolo[5,4-c]pyridin-

2-yl, and quinoxalin-2-yl (Table 4). In general, the

enzyme potencies did not vary greatly from linker to

linker in any given heterocyclic series (e.g., see 85, 89,

90, 92, 94, and 97). However, in most cases, a decrease

in potency was observed in comparison to the parent

piperazine linker, except perhaps for the (R)-2-hydroxy-

ethyl-pyrimidin-4-yl series.

Nonetheless, because the hypothesis was that the

increased lipophilicity was proposed to improve in vivo

activity, these compounds were all screened in the acute

in vivo assay at 1 mg/kg/day. For the most part, these

inhibitors performed better in this assay relative to their

parent piperazine congeners (data not shown). Those

that showed complete normalization of sciatic nerve

fructose were progressed to the chronic in vivo assay.

Results from the latter assay are shown in Table 4.

Interestingly, three of the four most potent compounds

were from the 4-hydroxymethyl-6-methylpyrimidin-2-

yl series (85, 89, and 94), and the fourth was from the

(R)-2-hydroxyethyl-pyrimidin-4-yl series (86).

The progression in SAR of the latter series is shown

in the compound progression 22 f 52 f 86 (Figure 4).

Starting with the symmetrical N,N′-bis-substituted

analogue 22, the intrinsic potency was increased by ∼6-

7× by replacing the (R)-hydroxyethyl groups with the

hydroxymethyl groups, providing compound 52. The

next big SAR advance occurred in the replacement of

the 2,6-dimethylpiperazine for the piperazine-linking

moiety, producing compound 86, which exhibited supe-

rior in vivo properties relative to its predecessor.

Overall, addition of these four properly placed methyl

groups provided a >20× increase in intrinsic activity

and at least a 15× increase in in vivo activity. On the

basis of both in vitro IC₅₀value and in vivo performance

in the chronic model, compound 86 was selected for

further preclinical profiling.

F igu r e 3. Rat pharmacokinetic profile of compounds 62, 67,

69, and I dosed orally at 5 mg/kg. Cp-166 572 (I) was dose-

normalized from a 20 mg/kg, po, PK study.

exemplify some of the fused bicyclic heterocycles that

were explored, with quinoxaline 69 showing good in vivo

activity.

Rat pharmacokinetic analysis of pyrimidine 62, ox-

azolopyridine 67, and quinoxaline 69 revealed good

systemic exposure and extended t_1/2(6, 6, and 3 h,

respectively) relative to the lead SDI I (0.5 h) (Figure

3). These increases in half-life of the heterocycle deriva-

tives, along with improved in vitro activity, have

resulted in an approximate 20-fold increase in acute in

vivo activity relative to I. On the basis of this result,

two compounds, 67 and 69, were advanced to the more

clinically relevant and challenging chronic in vivo

screen. However, their ED₉₀values for normalization

of sciatic nerve fructose were disappointingly high at

10 mg/kg/day and >20 mg/kg/day, respectively.

In order to improve the in vivo potency of these

compounds, attention was focused on modulating the

lipophilicity of the compounds. Because our initial target

is the peripheral nerve, which is wrapped by a fatty

myelin sheath, additional lipophilic methyl substituents

were appended to the piperazine nucleus to address

tissue penetration. That is, mono- and dimethyl piper-

Compound 86 selectively inhibits SDH and is inactive

against a number of other dehydrogenases including

Sorbitol Dehydrogenase Inhibitors

J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 2 517

Ta ble 4. Structure-Activity Relationships for Compounds 85-97: Effect of the Piperazine Linker

h-SDH IC₅₀

(µM) ( se

(n ) 3)

chronic

in vivo ED₉₀

(mg/kg/day)

compd no.

R¹

R²

R³

R⁵

R⁶

mp (°C)

85

86

87

88

89

90

91

92

93

94

95

96

97

4-hydroxymethyl-6-methyl-pyrimidin-2-yl

(R)-2-hydroxyethyl-pyrimidin-4-yl

oxazolo[5,4-c]pyridin-2-yl

â-Me

H

R-Me

â-Me

H

â-Me

H

â-Me

H

â-Me

H

139-141

163-164.5

175-178

0.10 ( 0.01

1

2

0.010 ( 0.001

0.27 ( 0.04

quinoxalin-2-yl

0.18 ( 0.06

1

4-hydroxymethyl-6-methyl-pyrimidin-2-yl

(R)-2-hydroxyethyl-pyrimidin-4-yl

4-hydroxymethyl-6-methyl-pyrimidin-2-yl

(R)-2-hydroxyethyl-pyrimidin-4-yl

4-hydroxymethyl-6-methyl-pyrimidin-2-yl

oxazolo[5,4-c]pyridin-2-yl

149-151

158-160

155-157

0.13 ( 0.02

0.20 ( 0.03

0.059 ( 0.025

0.17 ( 0.02

52% (1)

2

H

0.012 (0.002

0.080 ( 0.016

0.023 ( 0.006

0.099 ( 0.024

0.14 ( 0.027

â-Me

R-Me

H

quinoxalin-2-yl

4-hydroxymethyl-6-methyl-pyrimidin-2-yl

H

Con clu sion s

In conclusion, novel SDIs with heterocyclic groups

replacing the N,N-dimethylsulfamoyl moiety in I/II were

identified, which were orally effective, highly potent,

and long-acting in a key diabetic tissue. The following

are the SAR highlights leading to the discovery of 86,

the overall most promising SDI. Replacement of the

sulfamide group in CP-166 572 (I) with various hetero-

cycles provided modestly active (low micromolar) com-

pounds, demonstrating the initial potential of this

series. Incorporation of the (R)-hydroxyethyl moiety at

the pyrimidine 2-position provided a significant boost

in in vitro potency and provided compounds with a good

exposure and longer half-life. Although the potency and

pharmacokinetics of these new analogues appeared

sufficient to provide in vivo activity, there seemed to

be another factor that prevented these compounds from

achieving maximal activity. On the basis of the hypoth-

esis that penetration into the nerve tissue was a

contributing factor, modulation of the overall physical

properties of the compounds was accomplished by

installing methyl groups on the piperazine linker, which

dramatically improved in vivo potency, culminating in

identification of 86. Further testing of 86 showed it to

be a selective SDI with excellent pharmacokinetic and

pharmacodynamic properties. Additional aspects of the

metabolism of 86 in vitro and in different animal species

will be reported in due course.

F igu r e 4. SAR progression for compounds 22, 52, and 86.

Exp er im en ta l Section

F igu r e 5. Pharmacokinetic/pharmacodynamic relationship

for compound 86 (2 mg/kg/day).

Ch em istr y. Gen er a l Meth od s. Melting points were de-

termined on a Thomas-Hoover capillary melting point ap-

paratus and are uncorrected. H NMR spectra were obtained

lactate dehydrogenase, alcohol dehydrogenase, fructose

dehydrogenase, and glucose-6-phosphate dehydrogen-

ase. Pharmacokinetic/pharmacodynamic studies of

compound 86 in 5 day STZ diabetic rats demonstrated

a good correlation between sciatic nerve fructose nor-

malization and unbound serum drug concentrations

(Figure 5). Compound 86 at a single dose of 2 mg/kg/

day normalized sciatic nerve fructose for ∼17 h, with

some persistent effects even at the last time point (27

h).

1

on a Bruker AM-250, a Bruker AM-300, a Varian XL-300, or

a Varian Unity 400. Chemical shifts are reported in parts per

million (δ) relative to residual chloroform (7.26 ppm), dimethyl

sulfoxide (2.49 ppm), or methanol (3.30 ppm) as an internal

reference with coupling constants (J ) reported in hertz (Hz).

The peak shapes are denoted as follows: s, singlet; d, doublet;

t, triplet; q, quartet; m, multiplet; c, complex; br, broad.

Low-resolution mass spectra (MS) were obtained under

thermospray (TS) conditions on a Fisons Trio 1000 mass

spectrometer, under chemical ionization (CI) conditions on a

518 J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 2

Chu-Moyer et al.

Hewlett-Packard 5989A particle beam mass spectrometer,

under fast atom bombardment conditions (FAB) conditions on

a Kratos Concept 1S mass spectrometer, or under atmospheric

pressure chemical ionization (APCI) on a Fisons Platform II

spectrometer. Low-resolution gas chromatography (GC) mass

spectra were obtained on a Hewlett-Packard 5890 Series II

mass chromatograph. High-resolution mass spectra (HRMS)

were obtained under FAB conditions on a VG analytical ZAB

high field mass spectrometer by M-Scan Inc., West Chester,

PA 19830, or under electron impact (EI) conditions on a Kratos

Concept 1S mass spectrometer.

Optical rotations were obtained on a Perkin-Elmer 241 MC

polarimeter using a standard path length of 1 dcm. Liquid

column chromatography was performed using forced flow

(flash chromatography) of the indicated solvent on either

Baker Silica Gel (40 µm) or EM Sciences Silica Gel 60 in glass

columns. Elemental analyses were performed by Schwarzkopf

Microanalytical Laboratory, Inc., Woodside, NY 11377.

The terms “concentrated” and “evaporated” refer to the

removal of solvent using a rotary evaporator at water aspirator

pressure or at similar pressures generated by a Bu¨chi B-171

Vacobox or a Bu¨chi B-177 Vacobox with a bath temperature

equal to or less than 50 °C. Unless otherwise noted, reagents

were obtained from commercial sources and were used without

further purification.

was added Et₃N (0.55 mL, 3.96 mmol) followed by 2-chloro-

benzoxazole (6e, 0.37 mL, 2.85 mmol). This mixture was

allowed to stir at room temperature for 0.5 h and concentrated.

The residue was diluted with saturated aqueous NaHCO₃and

extracted with CHCl₃(2×). The combined organic extracts

were washed with water (1×) and brine (1×), dried (Na₂SO₄),

filtered, evaporated, and purified by flash column chromatog-

raphy (CHCl₃f 5% MeOH, CHCl₃) to give 0.46 g (71%) of

compound 7e as a light yellow solid. ¹H NMR (CDCl₃, 300

MHz) δ 8.28 (d, J ) 6.2 Hz, 1 H), 7.37 (d, J ) 7.7 Hz, 1 H),

7.27 (d, J ) 8.1 Hz, 1 H), 7.18 (td, J ) 7.7, 1.1 Hz, 1 H), 7.04

(td, J ) 7.7, 1.2 Hz, 1 H), 6.45 (d, J ) 6.2 Hz, 1 H), 4.49 (s, 2

H), 3.91-3.79 (c, 8 H), 3.52 (s, 3 H); MS (CI/NH₃) 326 (MH⁺).

Gen er a l P r oced u r e C. P r ep a r a tion of Com p ou n d s 7

g,h by Hyd r ogen a tion of Heter oa r om a tic Ch lor id e In -

ter m ed ia tes 7a ,b. A representative experimental procedure

for 7g is given below.

2-Meth oxym eth yl-4-(4-p yr im id in -4-yl-p ip er a zin -1-yl)-

p yr im id in e (7 g: R¹) P yr im id in -4-yl). A mixture of

chloropyrimidine 7a (50 mg, 0.16 mmol), 10% Pd/C (12.5 mg,

25 wt %), and NaOAc (25 mg, 0.31 mmol) in EtOH (50 mL)

was hydrogenated at 50 psi for 23 h on a Parr apparatus and

then filtered through Celite. The filtrate was evaporated, and

the residue was purified by flash column chromatography (5%

MeOH/CH₂Cl₂) to give 38 mg (84%) of compound 7g as a

colorless solid. ¹H NMR (CDCl₃, 300 MHz) δ 8.59 (s, 1 H), 8.24

(d, J ) 6.2 Hz, 1 H), 8.21 (d, J ) 6.3 Hz, 1 H), 6.48 (d, J ) 6.2

Hz, 1 H), 6.38 (d, J ) 6.2 Hz, 1 H), 4.45 (s, 2 H), 3.83-3.71 (c,

8 H), 3.48 (s, 3 H); MS (CI/NH₃) 287 (MH⁺).

2-Meth oxym eth yl-4-[4-(2-m eth oxym eth yl-p yr im id in -4-

yl)p ip er a zin -1-yl]p yr im id in e (8: R¹) 2-Meth oxym eth yl-

p yr im id in -4-yl). To a solution of 2-methoxymethyl-3H-

pyrimidin-4-one¹²(10.0 g, 71.4 mmol), DMAP (0.87 g, 7.14

mmol), and Et₃N (10.9 mL, 78.6 mmol) in CH₂Cl₂(200 mL) at

-78 °C was added Tf₂O (13.2 mL, 78.6 mmol) dropwise. This

mixture was allowed to stir at -78 °C for 1 h to give

2-methoxymethyl-pyrimidin-4-yl trifluoromethanesulfonate (1d),

which was used directly in the next reaction without workup

or isolation.

Piperazine (4, 6.14 g, 71.4 mmol) was added to the above,

and the mixture was slowly warmed to room temperature and

allowed to stir overnight, quenched with saturated aqueous

NaHCO₃, and extracted with dichloromethane (3×). The

combined organic extracts were dried (MgSO₄), filtered, evapo-

rated, and purified by flash column chromatography (10%

MeOH/EtOAc) followed by recrystallization (EtOAc) to give

compound 8 (3.60 g, 30% based on triflate 1d ) as a white solid.

¹H NMR (CDCl₃, 250 MHz) δ 8.28 (d, J ) 6.2 Hz, 2 H), 6.42

(d, J ) 6.2 Hz, 2 H), 4.51 (s, 4 H), 3.84-3.76 (c, 8 H), 3.53 (s,

6 H); MS (GC) 330 (M⁺).

2-Met h oxym et h ylp yr im id in -4-yl 2,4,6-Tr iisop r op yl-

ben zen esu lfon a te (1c). To a solution of 2-methoxymethyl-

3H-pyrimidin-4-one¹²(1.50 g, 10.7 mmol), DMAP (0.06 g, 0.15

mmol), and Et₃N (5.94 mL, 42.8 mmol) in CH₂Cl₂(45 mL) at

room temperature was added 2,4,6-triisopropylbenzenesulfonyl

chloride (3.90 g, 12.8 mmol). This mixture was allowed to stir

at room temperature for 30 min, concentrated, and purified

by flash column chromatography (CHCl₃f 1% MeOH/CHCl₃)

1

to give 3.96 g (91%) of compound 1c as a yellow oil. H NMR

(CDCl₃, 250 MHz) δ 8.72 (d, J ) 5.6 Hz, 1 H), 7.20 (s, 2 H),

6.98 (d, J ) 5.5 Hz, 1 H), 4.74 (s, 2 H), 4.17 (pentet, J ) 6.7

Hz, 2 H), 3.40 (s, 3 H), 2.92 (pentet, J ) 6.9 Hz, 1 H), 1.24 (d,

J ) 6.7 Hz, 18 H).

Gen er a l P r oced u r e A. P r ep a r a tion of Com p ou n d s

3a -k by Rea ction of Activa ted P yr im id in es 1a -c w ith

Su bstitu ted P ip er a zin es 2a-j. A representative experimen-

tal procedure for 3a is given below.

2-Met h oxym et h yl-4-(4-p h en yl-p ip er a zin -1-yl)p yr im i-

d in e (3a : R¹) P h en yl). To a solution of mesylate 1b¹³(0.72

g, 3.32 mmol) in DME (17 mL) was added Et₃N (1.38 mL, 9.96

mmol) followed by 1-phenyl-piperazine (2a , 0.76 mL, 4.98

mmol). This mixture was allowed to stir at reflux for 3 h, cooled

to room temperature, and concentrated. The residue was

diluted with saturated aqueous NaHCO₃and extracted with

CH₂Cl₂(3×). The combined organic extracts were dried

(Na₂SO₄), filtered, evaporated, and purified by flash

column chromatography (5% MeOH/CHCl₃) to give 0.64 g

(68%) of compound 3a as a yellow oil. ¹H NMR (CDCl₃, 300

MHz) δ 8.25 (d, J ) 6.2 Hz, 1 H), 7.32-7.26 (c, 2 H), 6.97-

6.88 (c, 3 H), 6.43 (d, J ) 6.2 Hz, 1 H), 4.49 (s, 2 H), 3.84-3.81

(c, 4 H), 3.52 (s, 3 H), 3.28-3.24 (c, 4 H); MS (CI/NH₃) 285

(MH⁺).

2-Meth oxym eth yl-4-p ip er a zin -1-yl-p yr im id in e (5). To

a solution of mesylate 1b (43.6 g, 0.20 mol) in THF (400 mL)

was added piperazine (4, 34.4 g, 0.4 mol). This mixture was

heated to reflux for 0.5 h, cooled to room temperature, and

filtered through Celite. The filtrate was concentrated to give

36.6 g (85%) of piperazino-pyrimidine 5 as a light tan solid.

¹H NMR (CDCl₃, 300 MHz) δ 8.22 (d, J ) 6.2 Hz, 1 H), 6.38

(d, J ) 6.2 Hz, 1 H), 4.46 (s, 2 H), 3.73-3.66 (c, 4H), 3.45

(s, 3 H), 3.03-2.93 (c, 4H), 2.45 (br s, 1 H); MS (TS) 219

(MH⁺).

4-(2-Meth oxym eth yl-p yr im id in -4-yl)p ip er a zin e-1-ca r -

boxylic Acid ter t-Bu tyl Ester (10). A mixture of chloride

1a (4.54 g, 28.6 mmol), Boc-piperazine (9, 7.68 g, 40.1 mmol),

and Et₃N (8.0 mL, 57.2 mmol) in THF (100 mL) was heated

to reflux for 3 h, cooled to room temperature, and filtered. The

filtrate was concentrated, and the residue was purified by flash

column chromatography (1 f 3% MeOH/CHCl₃) to give 8.7 g

1

(99%) of compound 10 as a reddish oil. H NMR (CDCl₃, 300

MHz) δ 8.23 (d, J ) 6.2 Hz, 1 H), 6.37 (d, J ) 6.2 Hz, 1 H),

4.56 (s, 2 H), 3.69-3.62 (c, 4 H), 3.54-3.46 (c, 4 H), 3.50 (s, 3

H), 1.46 (s, 9 H); MS (CI/NH₃) 309 (MH⁺).

4-(2-Hyd r oxym eth yl-p yr im id in -4-yl)p ip er a zin e-1-ca r -

boxylic Acid ter t-Bu tyl Ester (11). To a solution of meth-

oxymethyl compound 10 (0.74 g, 2.39 mmol) in CH₂Cl₂(8 mL)

at 0 °C with stirring under N₂was added Et₃N (66 µL, 0.48

mmol) followed by Me₂BBr (1.0 M in DCE, 3.11 mL, 3.11 mL).

The ice bath was removed, and this mixture was allowed to

stir at room temperature for 1.5 h and then quenched by the

careful addition of saturated aqueous NaHCO₃. The layers

were separated, and the aqueous phase was extracted with

10% i-PrOH/CHCl₃(3×). The combined organic extracts were

dried (Na₂SO₄), filtered, evaporated, and purified by flash

column chromatography (2.5 f 5% MeOH/CHCl₃) to give 0.54

g (76%) of the hydroxymethyl compound 11 as a pale yellow

Gen er a l P r oced u r e B. P r ep a r a tion of Com p ou n d s

7a -f by Rea ction of 2-Meth oxym eth yl-4-p ip er a zin -1-yl-

p yr im id in e (5) w ith Heter ocylic Ch lor id es 6a -f. A rep-

resentative experimental procedure for 7e is given below.

2-Meth oxym eth yl-4-(4-ben zoxa zol-2-yl-p ip er a zin -1-yl)-

p yr im id in e (7e: R ¹) Ben zoxa zol-2-yl). To a solution of

piperazino-pyrimidine 5 (0.41 g, 1.98 mmol) in i-PrOH (9 mL)

Sorbitol Dehydrogenase Inhibitors

J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 2 519

1

solid. H NMR (CDCl₃, 250 MHz) δ 8.22 (d, J ) 6.2 Hz, 1 H),

solid. mp 164-166 °C (dec); ¹H NMR (CDCl₃, 300 MHz) δ 8.32

(d, J ) 4.8 Hz, 2 H), 8.19 (d, J ) 6.2 Hz, 1 H), 6.54 (t, J ) 4.8

Hz, 1 H), 6.41 (d, J ) 6.2 Hz, 1 H), 4.60 (s, 2 H), 3.94-3.91 (c,

4 H), 3.76-3.73 (c, 4 H); MS (CI/NH₃) 273 (MH⁺). Anal.

(C₁₃H₁₆N₆O‚0.25H₂O) C, H, N.

[4-(4-P yr im idin -4-yl-piper azin -1-yl)pyr im idin -2-yl]m eth -

a n ol (17: R¹) P yr im d in -4-yl). Prepared from methyl ether

7g (BBr₃method) and purified by flash column chromatogra-

phy (5 f 10% MeOH/CH₂Cl₂) to give compound 17 (quant) as

a colorless solid. mp 185-186.5 °C; ¹H NMR (CD₃OD, 300

MHz) δ 8.49 (s, 1 H), 8.16 (app d, J ) 6.3 Hz, 2 H), 6.81 (d, J

) 6.4 Hz, 1 H), 6.69 (d, J ) 6.3 Hz, 1 H), 4.53 (s, 2 H), 4.01-

3.76 (c, 8 H). HRMS (EI) exact mass calcd for C₁₃H₁₆N₆O

272.1383 (M⁺), found 272.1375.

6.38 (d, J ) 6.2 Hz, 1 H), 4.59 (s, 2 H), 3.73-3.62 (c, 4 H),

3.57-3.48 (c, 4 H), 1.49 (s, 9 H).

[4-(4-P ip er a zin -1-yl)p yr im id in -2-yl]m eth a n ol Dih yd r o-

ch lor id e Sa lt (12). A heterogeneous mixture of Boc compound

11 (0.53 g. 1.82 mmol) and 4 N HCl/dioxane (13.7 mL, 54.6

mmol) was allowed to stir at room temperature for 3 h and

concentrated to give 0.48 g (99%) of the dihydrochloride salt

1

12 as a white solid. H NMR (CD₃OD, 250 MHz) δ 8.25 (d, J

) 6.2 Hz, 1 H), 7.19 (d, J ) 6.2 Hz, 1 H), 4.71 (s, 2 H), 4.39-

4.27 (c, 2 H), 4.17-4.01 (c, 2 H), 3.51-3.33 (c, 4 H).

{4-[4-(2,6-Dim eth yl-p yr im id in -4-yl)p ip er a zin -1-yl]p yr -

im id in -2-yl}m eth a n ol (21). A mixture of the dihydrochloride

12 (0.20 g, 0.74 mmol), 4-chloro-2,6-dimethyl-pyrimidine²⁷(13,

0.13 g, 0.74 mmol), and i-Pr₂NEt (2.54 mL, 14.7 mmol) in

n-BuOH was heated at reflux for 14 h, cooled to room

temperature, and filtered through Celite. The filtrate was

concentrated, diluted with saturated aqueous NaHCO₃, and

extracted with CHCl₃(4×). The combined organic extracts

were dried (Na₂SO₄), filtered, evaporated, and purified by flash

column chromatography (5% MeOH/CHCl₃) to give 0.085 g

(39%) of compound 21 as a white solid. mp 171.5-173.5 °C;

¹H NMR (CDCl₃, 300 MHz) δ 8.22 (d, J ) 6.2 Hz, 1 H), 6.39

(d, J ) 6.2 Hz, 1 H), 6.19 (s, 1 H), 4.60 (s, 2 H), 3.87-3.75 (c,

8 H), 2.49 (s, 3 H), 2.34 (s, 3 H); MS (CI/NH₃) 301 (MH⁺). Anal.

(C₁₅H₂₀N₆O‚0.25H₂O) C, H, N.

Gen er a l P r oced u r e D. P r ep a r a tion of Com p ou n d s 14-

20 a n d 22-33 by Dep r otection of th e Meth yl Eth er

P en u lt im a t e In t er m ed ia t es 3a -k , 7b -h , a n d 8. BBr ₃

Meth od. [4-(4-P h en yl-piper azin -1-yl)pyr im idin -2-yl]m eth -

a n ol (14: R¹) P h en yl). To a solution of methyl ether 7a

(0.64 g, 2.25 mmol) in CH₂Cl₂(22.5 mL) at 0 °C was added

BBr₃(1.0 M in CH₂Cl₂, 6.74 mL, 6.74 mmol). This mixture

was allowed to stir with warming to room temperature for 3

h, quenched by the slow addition of saturated aqueous

NaHCO₃, and stirred vigorously for 1 h. The layers were

separated, and the aqueous phase was extracted with 10%

i-PrOH/CHCl₃(3×). The combined organic extracts were dried

(Na₂SO₄), filtered, evaporated, and purified by flash column

chromatography (2% MeOH/CHCl₃) to give 0.54 g (89%) of

compound 14 as a white solid. mp 131-133 °C; ¹H NMR

(CDCl₃, 300 MHz) δ 8.21 (d, J ) 6.2 Hz, 1 H), 7.32-7.25 (c, 2

H), 6.97-6.89 (c, 3 H), 6.43 (d, J ) 6.2 Hz, 1 H), 4.61 (s, 2 H),

3.84-3.81 (c, 4 H), 3.28-3.25 (c, 4 H); MS (CI/NH₃) 271 (MH⁺).

Anal. (C₁₅H₁₈N₄O‚0.5H₂O) C, H, N.

Me₂BBr Meth od . {4-[4-(1H-Ben zim id a zol-2-yl)p ip er -

a zin -1-yl]p yr im id in -2-yl}m eth a n ol (24: R¹) 1H-Ben z-

im id a zol-2-yl). To a solution of methyl ether 3e (0.25 g, 0.77

mmol) in DCE (2.9 mL) at 0 °C was added Et₃N (21.5 µL, 0.15

mmol) followed by a solution of Me₂BBr (1.0 M in DCE, 1.0

mL, 1.0 mmol). The ice bath was removed, and this mixture

was allowed to stir at room temperature for 2.5 h, quenched

slowly with saturated aqueous NaHCO₃, and extracted with

10% i-PrOH/CHCl₃(3×). The combined organic extracts were

dried (Na₂SO₄), filtered, evaporated, and purified by flash

column chromatography (CHCl₃f 10% MeOH/CHCl₃) to give

compound 24 (75%) as a light yellow solid. mp 235-237 °C

(dec); ¹H NMR (CD₃OD, 250 MHz) δ 8.15 (d, J ) 6.3 Hz, 1 H),

7.24-7.27 (c, 2 H), 6.99-7.03 (c, 2 H), 6.74 (d, J ) 6.3 Hz, 1

H), 4.53 (s, 2 H), 3.90-3.94 (c, 4 H), 3.61-3.65 (c, 4 H); MS

(CI/NH₃) 311 (MH⁺). Anal. (C₁₆H₁₈N₆O‚0.25H₂O) C, H, N.

[4-(4-P yr id in -2-yl-p ip er a zin -1-yl)p yr im id in -2-yl]m eth -

a n ol (15: R¹) P yr id in -2-yl). Prepared from methyl ether

7b (BBr₃method) and purified by flash column chromatogra-

phy (2 f 5% MeOH/CHCl₃) to give compound 15 (82%) as a

white solid. mp 139-141 °C; ¹H NMR (CDCl₃, 300 MHz) δ

8.20-8.17 (c, 2 H), 7.50 (m, 1 H), 6.67-6.63 (c, 2 H), 6.40 (d,

J ) 6.2 Hz, 1 H), 4.59 (s, 2 H), 3.81-3.74 (c, 4 H), 3.67-3.64

(c, 4 H); MS (CI/NH₃) 272 (MH⁺). Anal. (C₁₄H₁₇N₅O‚0.25H₂O)

C, H, N.

[4-(4-P yr a zin -2-yl-p ip er a zin -1-yl)p yr im id in -2-yl]m eth -

a n ol (18: R¹) P yr a zin -2-yl). Prepared from methyl ether

3d (BBr₃method) and purified by flash column chromatogra-

phy (1 f 3% MeOH/CH₂Cl₂) to give compound 18 (95%) as a

1

white foam. H NMR (CDCl₃, 300 MHz) δ 8.24 (d, J ) 6.2 Hz,

1 H), 8.18 (s, 1 H), 8.11 (d, J ) 1.7 Hz, 1 H), 7.92 (d, J ) 1.7

Hz, 1 H), 6.43 (d, J ) 6.2 Hz, 1 H), 4.52 (s, 2 H), 3.89-3.78 (c,

4 H), 3.78-3.68 (c, 4 H). HRMS (FAB) exact mass calcd for

C

₁₃H₁₇N₆O 273.1464 (MH⁺), found 273.1467.

[4-(4-[1,3,5]Tr ia zin -2-yl-p ip er a zin -1-yl)p yr im id in -2-yl]-

m eth a n ol (19: R¹) [1,3,5]-Tr ia zin -2-yl). Prepared from

methyl ether 7h (BBr₃method) and purified by flash column

chromatography (1 f 2.5% MeOH/CH₂Cl₂) to give compound

19 (54%) as a colorless solid. mp 195-196.5 °C; ¹H NMR

(CDCl₃, 300 MHz) δ 8.56 (s, 2 H), 8.23 (d, J ) 6.2 Hz, 1 H),

6.42 (d, J ) 6.2 Hz, 1 H), 4.60 (s, 2 H), 4.02-3.92 (c, 4 H),

3.81-3.70 (c, 4 H). HRMS (EI) exact mass calcd for C₁₂H₁₅N₇O

273.1336 (M⁺), found 273.1323.

{4-[4-(4,6-Dim eth yl-p yr im id in -2-yl)p ip er a zin -1-yl]p yr -

im id in -2-yl}m eth a n ol (20: R¹) 4,6-Dim eth yl-p yr im id in -

2-yl). Prepared from methyl ether 7c (BBr₃method) and

purified by flash column chromatography (1 f 10% MeOH/

CHCl₃and then 1% NH₄OH in 10% MeOH/CHCl₃) to give

compound 20 (90%) as a yellow solid. mp 175-176 °C; ¹H NMR

(CDCl₃, 300 MHz) δ 8.20 (d, J ) 6.1 Hz, 1 H), 6.41 (d, J ) 6.2

Hz, 1 H), 6.31 (s, 1 H), 4.60 (s, 2 H), 3.97-3.90 (c, 4 H), 3.79-

3.70 (c, 4 H), 2.29 (s, 6 H); MS (APCI) 301 (MH⁺). Anal.

(C₁₅H₂₀N₆O‚0.25H₂O) C, H, N.

{4-[4-(2-Hyd r oxym eth yl-p yr im id in -4-yl)p ip er a zin -1-yl]-

p yr im id in -2-yl}m eth a n ol (22: R¹) 2-Hyd r oxym eth yl-

p yr im id in -4-yl). Prepared from methyl ether 8 (BBr₃method)

and tritrated with EtOAc to give compound 22 (65%) as a white

solid. mp 237-239 °C (dec); ¹H NMR (CD₃OD, 400 MHz) δ

8.14 (d, J ) 6.2 Hz, 2 H), 6.67 (d, J ) 6.4 Hz, 2 H), 4.52 (s,

4 H), 3.30-3.24 (c, 8 H); MS (APCI) 304 (MH⁺). Anal.

(C₁₄H₁₈N₆O₂‚0.67H₂O) C, H; N: calcd, 26.73; found, 26.30.

{4-[4-(4,6-Dich lor o[1,3,5]tr iazin -2-yl)piper azin -1-yl]pyr -

im idin -2-yl}m eth an ol (23: R¹) 4,6-Dich lor o[1,3,5]tr iazin -

2-yl). Prepared from methyl ether 7b (BBr₃method) and

purified by flash column chromatography (1 f 2% MeOH/

CH₂Cl₂) to give compound 23 (66%) as a white solid. mp 250-

255 °C (dec); ¹H NMR (CDCl₃, 300 MHz) δ 8.26 (d, J ) 6.2

Hz, 1 H), 6.44 (d, J ) 6.2 Hz, 1 H), 4.62 (s, 2 H), 4.07-3.92 (c,

4 H), 3.84-3.72 (c, 4 H). HRMS (EI) exact mass calcd for

C

₁₂H₁₃Cl₂N₇O 341.0558 (M⁺), found 341.0517.

[4-(1-E t h yl-1H -b en zim id a zol-2-yl-p ip er a zin -1-yl)p yr -

im id in -2-yl]m eth a n ol (25: R¹) 1-Eth yl-1H-ben zim id a zol-

2-yl). Prepared from methyl ether 3f (BBr₃method) and

purified by flash column chromatography (CHCl₃f 5% MeOH/

CHCl₃) to give compound 25 (43%) as a white solid. mp 124-

126 °C (dec); ¹H NMR (CDCl₃, 300 MHz) δ 8.23 (d, J ) 6.2

Hz, 1 H), 7.61 (m, 1 H), 7.26 (m, 1 H), 7.22-7.16 (c, 2 H), 6.46

(d, J ) 6.2 Hz, 1 H), 4.61 (s, 2 H), 4.11 (q, J ) 7.2 Hz, 2 H),

3.88-3.84 (c, 4 H), 3.52-3.37 (c, 4 H), 1.47 (t, J ) 7.2 Hz, 1

H); MS (CI/NH₃) 339 (MH⁺). Anal. (C₁₈H₂₂N₆O‚0.25H₂O) C,

H, N.

[4-(4-P yr im idin -2-yl-piper azin -1-yl)pyr im idin -2-yl]m eth -

a n ol (16: R¹) P yr im id in -2-yl). Prepared from methyl ether

7c (BBr₃method) and purified by flash column chromatogra-

phy (5% MeOH/CHCl₃) to give compound 16 (76%) as a white

[4-(Ben zot h ia zol-2-yl-p ip er a zin -1-yl)p yr im id in -2-yl]-

m eth a n ol (26: R¹) Ben zoth ia zol-2-yl). Prepared from

methyl ether 7d (BBr₃method) and purified by flash column

chromatography (CHCl₃f 5% MeOH/CHCl₃) to give compound

520 J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 2

Chu-Moyer et al.

1

26 (62%) as a white solid. mp 192-193 °C; H NMR (CDCl₃,

1 H), 6.47 (d, J ) 6.2 Hz, 1 H), 4.63 (s, 2 H), 3.94-3.90 (c, 8

H); MS (APCI) 323 (MH⁺). Anal. (C₁₇H₁₈N₆O‚H₂O) C, N; H:

calcd, 5.92; found, 5.25.

Gen er a l P r oced u r e K. P r ep a r a tion of Com p ou n d s

35a -d Via Dep r otection of N-Ben zyl Der iva tives 47a -

d . A representative experimental procedure for 35a is given

below.

1-(4,6-Bis-t r iflu or om et h yl-p yim id in -2-yl)p ip er a zin e

(35a : R ) R′ ) Tr iflu or om eth yl). To a solution of N-benzyl

compound 47a (0.73 g, 1.80 mmol theory) in MeOH (10 mL)

was added HCO₂NH₄(1.18 g, 18.7 mmol) and 10% Pd/C (145

mg, 20 wt %). This mixture was allowed to stir at reflux for

18 h, cooled to room temperature, filtered through Celite, and

concentrated. The residue was purified by flash column

chromatography (CHCl₃f 10% MeOH/CHCl₃) to give 0.38 g

(75% from 45) of piperazine 35a as a yellow solid. ¹H NMR

(CDCl₃, 250 MHz) δ 7.01 (s, 1 H), 4.03-3.82 (c, 4 H), 3.10-

2.88 (c, 4 H); MS (CI/NH₃) 301 (MH⁺).

300 MHz) δ 8.25 (d, J ) 6.2 Hz, 1 H), 7.62 (d, J ) 8.3 Hz, 1

H), 7.58 (d, J ) 8.0 Hz, 1 H), 7.32 (td, J ) 7.7, 1.1 Hz, 1 H),

7.11 (td, J ) 7.7, 1.1 Hz, 1 H), 6.45 (d, J ) 6.2 Hz, 1 H), 4.61

(s, 2 H), 3.87-3.83 (c, 4 H), 3.77-3.73 (c, 4 H); MS (CI/NH₃)

328 (MH⁺). Anal. (C₁₆H₁₇N₅OS) C, H, N.

[4-(4-Ben zoxa zol-2-yl-p ip er a zin -1-yl)p yr im id in -2-yl]-

m eth a n ol (27: R¹) Ben zoxa zol-2-yl). Prepared from meth-

yl ether 7e (BBr₃method) and purified by flash column

chromatography (CHCl₃f 5% MeOH/CHCl₃) to give compound

27 (76%) as a white solid. mp 200-201.5 °C; ¹H NMR (CDCl₃,

300 MHz) δ 8.25 (d, J ) 6.2 Hz, 1 H), 7.38 (d, J ) 7.7 Hz, 1

H), 7.27 (d, J ) 7.5 Hz, 1 H), 7.19 (td, J ) 7.7, 1.1 Hz, 1 H),

7.05 (td, J ) 7.7, 1.2 Hz, 1 H), 6.45 (d, J ) 6.2 Hz, 1 H), 4.62

(s, 2 H), 3.85-3.79 (c, 8 H); MS (CI/NH₃) 312 (MH⁺). Anal.

(C₁₆H₁₇N₅O₂‚0.25H₂O) C, H, N.

{4-[4-(1,1-Dioxo-1H-ben zo[d ]isoth ia zol-3-yl)p ip er a zin -

1-yl]p yr im id in -2-yl}m eth a n ol (28: R¹) 1H-Ben zo[d ]-

isoth ia zol-3-yl S,S-Dioxid e). Prepared from methyl ether 3k

(Me₂BBr method) and purified by flash column chromatogra-

phy (CHCl₃f 4% MeOH/CHCl₃) to give compound 28 (61%)

as a pale yellow solid. mp 278-281 °C (dec); ¹H NMR (DMSO-

d₆, 250 MHz) δ 8.24 (d, J ) 5.4 Hz, 2 H), 8.04 (d, J ) 6.4 Hz,

1 H), 7.90-7.80 (c, 2 H), 6.66 (d, J ) 6.0 Hz, 1 H), 4.89 (t, J )

5.8 Hz, 1 H), 4.39 (d, J ) 5.8 Hz, 1 H), 4.15-3.85 (c, 8 H); MS

(CI/NH₃) 360 (MH⁺). Anal. (C₁₆H₁₇N₅O₃S‚0.25H₂O) C, H, N.

[4-(4-Ben zo[d ]isoth ia zol-3-yl-p ip er a zin -1-yl)p yr im id in -

2-yl]m eth a n ol (29: R¹) Ben zo[d ]isoth ia zol-3-yl). Pre-

pared from methyl ether 3g (Me₂BBr method) and purified by

flash column chromatography (CHCl₃f 3% MeOH/CHCl₃) to

give compound 29 (90%) as a pale yellow solid. mp 134-136

Gen er a l P r oced u r e E. P r ep a r a tion of Com p ou n d s

36a -h ,j-o by Rea ction of Activa ted P yr im id in es 34a -c

w ith Su bstitu ted P ip er a zin es 2 g-j a n d 35a -j. A repre-

sentative experimental procedure for 36j is given below.

(R)-1-[4-(4-Oxa zolo[4,5-b]p yr id in -2-yl-p ip er a zin -1-yl)-

p yr im id in -2-yl]eth yl Bu tyr a te (36j: R ) Bu tyr yl, R¹

)

Oxa zolo[4,5-b]p yr id in -2-yl). To a solution of chlorobutyrate

34c (0.15 g, 0.73 mmol)¹³in i-PrOH (7 mL) was added Et₃N

(0.23 mL, 2.0 mmol) followed by 1-(oxazolo[4,5-b]pyridin-2-yl)-

piperazine²⁸(35e, 0.15 g, 0.73 mmol). This mixture was heated

at reflux for 15 h, cooled to room temperature, and evaporated.

The residue was diluted with saturated aqueous NaHCO₃and

extracted with CHCl₃(3×). The combined organic extracts

were dried (Na₂SO₄), filtered, evaporated, and purified by flash

column chromatography (1.5% MeOH/CHCl₃) to give 0.26 g

(100%) of compound 36j as a colorless oil. ¹H NMR (CDCl₃,

250 MHz) δ 8.33-8.24 (c, 2 H), 7.48 (dd, J ) 7.8, 1.4 Hz, 1 H),

6.96 (dd, J ) 7.9, 5.2 Hz, 1 H), 6.44 (d, J ) 6.2 Hz, 1 H), 5.70

(q, J ) 6.8 Hz, 1 H), 3.99-3.73 (c, 8 H), 2.41 (t, J ) 7.5 Hz, 2

H), 1.81-1.66 (c, 2 H), 1.60 (d, J ) 6.7 Hz, 3 H), 0.98 (t, J )

7.4 Hz, 3 H); MS (TS) 397 (MH⁺).

1

°C (dec); H NMR (CDCl₃, 250 MHz) δ 8.25 (d, J ) 6.2 Hz, 1

H), 7.94 (d, J ) 8.0 Hz, 1 H), 7.85 (d, J ) 8.0 Hz, 1 H), 7.52

(td, J ) 7.5, 0.9 Hz, 1 H), 7.41 (td, J ) 7.5, 0.9 Hz, 1 H), 6.48

(d, J ) 6.2 Hz, 1 H), 4.63 (s, 2 H), 3.93-3.89 (c, 4 H), 3.67-

3.63 (c,

N₅OS‚0.5H₂O) C, H, N.

4 -

H); MS (CI/NH₃) 328 (MH⁺). Anal. (C₁₆H₁₇

[4-(4-Ben zo[d ]isoxa zol-3-yl-p ip er a zin -1-yl)p yr im id in -

2-yl]m eth a n ol (30: R¹) Ben zo[d ]isoxa zol-3-yl). Prepared

from methyl ether 3h (BBr₃method) and purified by flash

column chromatography (CHCl₃f 1% MeOH/CHCl₃) to give

compound 29 (63%) as a light yellow solid. mp 139-141.5 °C

(R)-1-(4-P ip er a zin -1-yl-p yr im id in -2-yl)et h yl Acet a t e

(37a ). A mixture of mesyl acetate 34b (24.1 g, 92 mmol) and

piperazine (4, 16.0 g, 184 mmol) in THF (200 mL) was allowed

to stir at reflux for 2 h, cooled to room temperature, and

filtered. The filtrate was concentrated and purified by flash

column chromatography (10% MeOH/CH₂Cl₂) to give 24.4 g

1

(dec); H NMR (CDCl₃, 250 MHz) δ 8.25 (d, J ) 6.2 Hz, 1 H),

7.72 (d, J ) 8.0 Hz, 1 H), 7.53-7.46 (c, 2 H), 7.25 (m, 1 H),

6.47 (d, J ) 6.2 Hz, 1 H), 4.63 (s, 2 H), 3.93-3.88 (c, 4 H),

3.71-3.66 (c, 4 H); MS (APCI) 312 (MH⁺). Anal. (C₁₆H₁₇N₅O₂‚

0.5H₂O) C, H, N.

1

(88%) of compound 37a as a pale yellow oil. H NMR (CDCl₃,

250 MHz) δ 8.19 (d, J ) 6.2 Hz, 1 H), 6.34 (d, J ) 6.2 Hz, 1

H), 5.66 (q, J ) 6.8 Hz, 1 H), 3.68-3.57 (c, 4 H), 2.98-2.89 (c,

4 H), 2.15 (s, 3 H), 1.58 (d, J ) 6.8 Hz, 3 H); MS (CI/NH₃) 251

(MH⁺).

[4-(4-Isoq u in olin -1-yl-p ip er a zin -1-yl)p yr im id in -2-yl]-

m eth a n ol (31: R¹) Isoqu in olin -1-yl). Prepared from meth-

yl ether 3i (Me₂BBr method) and purified by flash column

chromatography (1% MeOH/CHCl₃) to give compound 31 (70%)

as a yellow solid. mp 144-145 °C; ¹H NMR (CDCl₃, 250 MHz)

δ 8.25 (d, J ) 6.2 Hz, 1 H), 8.18-8.13 (c, 2 H), 7.80 (d, J ) 8.3

Hz, 1 H), 7.66 (td, J ) 7.5, 1.2 Hz, 1 H), 7.56 (td, J ) 7.5, 1.2

Hz, 1 H), 7.33 (d, J ) 5.8 Hz, 1 H), 6.49 (d, J ) 6.2 Hz, 1 H),

4.63 (s, 2 H), 3.96-3.92 (c, 4 H), 3.54-3.50 (c, 4 H); MS (APCI)

322 (MH⁺). Anal. (C₁₈H₁₉N₅O‚0.75H₂O) C, H, N.

[4-(4-Qu in olin -2-yl-piper azin -1-yl)pyr im idin -2-yl]m eth -

a n ol (32: R¹) Qu in olin -2-yl). Prepared from methyl ether

3j (Me₂BBr method) and purified by flash column chromatog-

raphy (1% MeOH/CHCl₃) to give compound 32 (73%) as a

yellow solid. mp 172-174 °C (dec); ¹H NMR (CDCl₃, 300 MHz)

δ 8.22 (d, J ) 6.2 Hz, 1 H), 7.95 (d, J ) 9.1 Hz, 1 H), 7.73 (d,

J ) 8.4 Hz, 1 H), 7.63 (d, J ) 7.5 Hz, 1 H), 7.56 (d, J ) 8.4 Hz,

1 H), 7.25 (t, J ) 7.5 Hz, 1 H), 6.99 (d, J ) 9.1 Hz, 1 H), 6.43

(d, J ) 6.2 Hz, 1 H), 4.62 (s, 2 H), 3.88-3.85 (c, 8 H); MS (APCI)

322 (MH⁺). Anal. (C₁₈H₁₉N₅O‚0.75H₂O) C, H, N.

(R)-1-(4-P ip er a zin -1-yl-p yr im id in -2-yl)et h a n ol (37b ).

To a solution of acetate 37a (1.13 g, 4.51 mmol) in a 3:1:1

mixture of THF/MeOH/H₂O (45 mL) was added LiOH‚H₂O

(0.57 g, 13.5 mmol). This mixture was allowed to stir at room

temperature for 45 min and concentrated. The aqueous residue

was extracted with 10% i-PrOH/CHCl₃(3×), and the combined

organic extracts were dried (Na₂SO₄), filtered, and evaporated

to give 0.86 g (92%) of compound 37b as a yellow oil. ¹H NMR

(CDCl₃, 300 MHz) δ 8.18 (d, J ) 6.2 Hz, 1 H), 6.34 (d, J ) 6.2

Hz, 1 H), 4.69 (q, J ) 6.8 Hz, 1 H), 3.72-3.61 (c, 4 H), 3.03-

2.92 (c, 4 H), 1.51 (d, J ) 6.8 Hz, 3 H); MS (CI/NH₃) 209 (MH⁺).

Gen er a l P r oced u r e F . P r ep a r a tion of Com p ou n d s

39a -d by Rea ction of (R)-1-(4-P ip er a zin -1-yl-p yr im id in -

2-yl)eth yl Aceta te (37a ) w ith Heter ocyclic Ch lor id es

6c,e, 13, a n d 38. A representative experimental procedure for

39a is given below.

(R)-1-{4-[4-(4,6-Dim et h yl-p yr im id in -2-yl)p ip er a zin -1-

[4-(4-Qu in a zolin -4-yl-p ip er a zin -1-yl)p yr im id in -2-yl]-

m eth a n ol (33: R¹) Qu in a zolin -4-yl). Prepared from methyl

ether 7f (Me₂BBr method) and purified by flash column

chromatography (1 f 2% MeOH/CHCl₃) to give compound 33

(63%) as an off-white solid. mp 207.5-209 °C; ¹H NMR (CDCl₃,

300 MHz) δ 8.79 (s, 1 H), 8.26 (d, J ) 6.2 Hz, 1 H), 7.95 (d, J

) 8.4 Hz, 1 H), 7.79 (t, J ) 7.8 Hz, 1 H), 7.52 (t, J ) 7.8 Hz,

yl]p yr im id in -2-yl}eth yl a ceta te (39a : R ) Acetyl, R¹

)

4,6-Dim eth yl-p yr im id in -2-yl). To a solution of piperazino-

pyrimidine 37a (0.56 g, 2.26 mmol) in n-BuOH (7.5 mL) was

added i-Pr₂NEt (0.79 mL, 4.52 mmol) followed by 2-chloro-

4,6-dimethylpyrimidine²⁹(6c, 0.15 g, 0.73 mmol). This mixture

was heated at reflux for 12 h, cooled to room temperature, and

evaporated. The residue was diluted with saturated aqueous

Sorbitol Dehydrogenase Inhibitors

J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 2 521

NaHCO₃and extracted with CHCl₃(3×). The combined organic

extracts were dried (Na₂SO₄), filtered, evaporated, and purified

by flash column chromatography (EtOAc) to give 0.52 g (65%)

of compound 39a as a yellow solid. ¹H NMR (CDCl₃, 300 MHz)

δ 8.20 (d, J ) 6.2 Hz, 1 H), 6.38 (d, J ) 6.2 Hz, 1 H), 6.31 (s,

1 H), 5.67 (q, J ) 6.8 Hz, 1 H), 3.96-3.86 (c, 4 H), 3.75-3.67

(c, 4 H), 2.29 (s, 6 H), 2.15 (s, 3 H), 1.58 (d, J ) 6.8 Hz, 3 H);

MS (CI/NH₃) 357 (MH⁺).

i-PrOH (8.5 mL) for 15 min] was added guanidine bis-

(trifluroracetate) salt 45 (0.71 g, 1.70 mmol) followed by an

additional aliquot of freshly distilled i-PrOH (8.5 mL). After

the solution was refluxed for 1 h, hexafluoro-2,4-pentanedione

(46a , 2.4 mL, 17.0 mmol) was added and the resulting mixture

was allowed to stir at reflux for 19 h, cooled to room temper-

ature, and concentrated. The residue was suspended in

saturated aqueous NaHCO₃and extracted with CHCl₃(3×).

The combined organic extracts were dried (Na₂SO₄), filtered,

evaporated, and purified by flash column chromatography (1%

MeOH/CHCl₃) to give 0.73 g (>100%) of pyrimidinyl-piperazine

1R-(4-{4-[2-(1R-Bu tyr loxy-eth yl)p yr im id in -4-yl]p ip er -

a zin -1-yl}p yr im id in -2-yl)eth yl Bu tyr a te (40: R ) Bu -

tyr yl, R¹) (R)-2-(1-Bu tyr loxy-eth yl)p yr im id in -4-yl). A

mixture of chlorobutyrate 34c (0.53 g, 2.32 mmol), piperazine

(4, 0.10 g, 1.16 mmol), and Et₃N (0.48 mL, 3.48 mmol) in

i-PrOH (11 mL) was heated at reflux for 18 h, cooled to room

temperature, and concentrated. The residue was diluted with

saturated aqueous NaHCO₃and extracted with CHCl₃(3×).

The combined organic extracts were dried (Na₂SO₄), filtered,

evaporated, and purified by flash column chromatography (3%

MeOH/CHCl₃) to give 0.49 g (90%) of compound 40 as an off-

1

47a as a yellow oil. H NMR (CDCl₃, 250 MHz) δ 7.39-7.26

(c, 5 H), 6.98 (s, 1 H), 3.99-3.88 (c, 4 H), 3.57 (s, 2 H), 2.57-

2.48 (c, 4 H); MS (CI/NH₃) 391 (MH⁺).

(R)-1-{4-[4-(4-Meth yl-6-ph en yl-pyr im idin -2-yl)piper azin -

1-yl]p yr im id in -2-yl}eth a n ol (63: R ) Meth yl, R′ ) P h en -

yl). Prepared from pyrimidino-piperazine 49 and 1-benzoyl-

acetone (46e) and purified by flash column chromatography

(CHCl₃f 10% MeOH/CHCl₃) to give compound 63 (94%) as a

yellow sticky material. [R]_D+13.5 (c 1.3, MeOH); ¹H NMR

(CDCl₃, 250 MHz) δ 8.24 (d, J ) 6.2 Hz, 1 H), 8.20-8.10 (c, 2

H), 7.52-7.43 (c, 3 H), 6.95 (s, 1 H), 6.44 (d, J ) 6.2 Hz, 1 H),

4.74 (q, J ) 6.6 Hz, 1 H), 4.37 (br s, 1 H), 4.12-4.03 (c, 4 H),

3.85-3.76 (c, 4 H), 2.45 (s, 3 H), 1.54 (d, J ) 6.6 Hz, 3 H); MS

(TS) 377 (MH⁺). Anal. (C₂₁H₂₄N₆O) C, H, N.

1

white solid. H NMR (CDCl₃, 400 MHz) δ 8.23 (d, J ) 6.0 Hz,

2 H), 6.36 (d, J ) 6.2 Hz, 2 H), 5.67 (q, J ) 6.8 Hz, 2 H), 3.84-

3.66 (c, 8 H), 2.39 (t, J ) 7.5 Hz, 4 H), 1.73-1.62 (c, 4 H), 1.57

(d, J ) 6.8 Hz, 6 H), 0.95 (t, J ) 7.5 Hz, 6 H); MS (APCI) 471

(MH⁺).

Gen er a l P r oced u r e H. P r ep a r a tion of Bis(Boc)-gu a n i-

d in es 44 a n d 48 Usin g N,N′-Bis(ter t-bu toxyca r bon yl)-

th iou r ea (43). 4-Ben zyl-piper azin e-1-N,N′-bis(ter t-bu toxy-

ca r b on yl)ca r b oxa m id in e (44). To a solution of 1-benzyl-

piperazine (42, 1.14 mL, 6.58 mmol) and N,N′-bis(tert-butoxy-

carbonyl)thiourea³⁰(43, 2.00 g, 7.24 mmol) in DMF (13 mL)

at 0 °C was added Et₃N (1.83 mL, 13.2 mmol) and HgCl₂(1.97

g, 7.24 mmol). This mixture was allowed to warm to room

temperature slowly, stirred overnight, diluted with Et₂O, and

washed with H₂O (3×) and brine (1×). The organic phase was

dried (Na₂SO₄), filtered, and evaporated to give 2.87 g (crude,

>100%) of compound 44 as a yellow sticky foam, which was

(R)-1-{4-[4-(4-P h en yl-pyr im idin -2-yl)piper azin -1-yl]pyr -

im id in -2-yl}eth a n ol (64: R ) Hyd r ogen , R′ ) P h en yl).

Prepared from pyrimidino-piperazine 49 and 3-(dimethyl-

amino)-1-phenyl-propenone³¹(46f) and purified by flash col-

umn chromatography (CHCl₃f 10% MeOH/CHCl₃) to give

compound 64 (93%) as a reddish oil. [R]_D+12.9 (c 1.8, MeOH);

¹H NMR (CDCl₃, 250 MHz) δ 8.42 (d, J ) 5.2 Hz, 1 H), 8.25

(d, J ) 6.2 Hz, 1 H), 8.11-8.02 (c, 2 H), 7.53-7.44 (c, 3 H),

7.03 (d, J ) 5.2 Hz, 1 H), 6.45 (d, J ) 6.2 Hz, 1 H), 4.74 (q, J

) 6.8 Hz, 1 H), 4.35 (br s, 1 H), 4.11-4.04 (c, 4 H), 3.89-3.76

(c, 4 H), 1.54 (d, J ) 6.6 Hz, 3 H); MS (TS) 363 (MH⁺). Anal.

(C₂₀H₂₂N₆O‚0.25H₂O) C, H, N.

1

used directly in the next step. H NMR (CDCl₃, 250 MHz) δ

7.36-7.20 (c, 5 H), 3.71-3.55 (c, 4 H), 3.53 (s, 2 H), 2.57-2.44

(c, 4 H), 1.52 (s, 9 H), 1.48 (s, 9 H); MS (CI/NH₃) 419 (MH⁺).

(R)-4-[2-(1-Acetoxy-eth yl)p yr im id in -4-yl]p ip er a zin e-1-

N,N′-bis(ter t-bu toxyca r bon yl)ca r boxa m id in e (48). Pre-

pared from piperazino-pyrimidine 37a , to give compound 48

(100%) as a yellow foam. ¹H NMR (CDCl₃, 300 MHz) δ 8.23

(d, J ) 6.2 Hz, 1 H), 6.36 (d, J ) 6.2 Hz, 1 H), 5.67 (q, J ) 6.8

Hz, 1 H), 3.80-3.63 (c, 8 H), 2.15 (s, 3 H), 1.57 (d, J ) 6.8 Hz,

3 H), 1.51 (s, 9 H), 1.49 (s, 9 H); MS (TS) 493 (MH⁺).

Gen er a l P r oced u r e G. P r ep a r a tion of Com p ou n d s 50-

62 a n d 65-70 by Hyd r olysis of th e Ester P r otectin g

Gr ou p in P en u ltim a te In ter m ed ia tes 36a -g,i-o, 39a -

d , a n d 40. LiOH Meth od . (R)-1-[4-(4-Oxa zolo[4,5-b]p yr i-

d in -2-yl-p ip er a zin -1-yl)p yr im id in -2-yl]eth a n ol (65: R¹

)

Oxa zolo[4,5-b]p yr id in -2-yl). To a solution of butyrate 36j

(0.26 g, 0.66 mmol) in a 3:1:1 mixture of THF/MeOH/H₂O (12

mL) at 0 °C was added LiOH‚H₂O (36 mg, 0.85 mmol). This

mixture was slowly warmed to room temperature, stirred for

2 h, and evaporated. The residue was diluted with H₂O and

extracted with CHCl₃(4×). The combined organic extracts

were dried (Na₂SO₄), filtered, evaporated, and purified by flash

column chromatography (2% MeOH/CHCl₃) to give 0.15 g

(69%) of compound 65 as a white solid. mp 190-191.5 °C; [R]_D

+14.5 (c 1.1, MeOH); ¹H NMR (CDCl₃, 300 MHz) δ 8.27-8.24

(c, 2 H), 7.47 (dd, J ) 8.0, 1.4 Hz, 1 H), 6.95 (dd, J ) 7.8, 5.1

Hz, 1 H), 6.46 (d, J ) 6.2 Hz, 1 H), 4.72 (q, J ) 6.6 Hz, 1 H),

4.25 (br s, 1 H), 3.87-3.85 (c, 8 H), 1.51 (d, J ) 6.6 Hz, 3 H);

MS (CI/NH₃) 327 (MH⁺). Anal. (C₁₆H₁₈N₆O₂) C, H, N.

Gen er a l P r oced u r e I. P r ep a r a tion of Gu a n id in e Bis-

(tr iflu or oa ceta te) Sa lts 45 a n d 49 by TF A Dep r otection

of Bis(Boc)-gu a n id in es 44 a n d 48. 4-Ben zyl-p ip er a zin e-

1-ca r boxa m id in e bis(tr iflu or oa ceta te) Sa lt (45). To a

solution of bis(Boc)-guanidine 44 (2.87 g, 6.58 mmol theory)

in CH₂Cl₂(52.5 mL) was added TFA (17.5 mL, 25% v/v). This

mixture was allowed to stir at room temperature for 3 h,

concentrated, and chased with EtOH (1×) and Et₂O (1×) to

give 2.70 g (94% from 42) of guanidine bis(trifluoroacetate)

1

salt 45 as a white solid. H NMR (CD₃OD, 250 MHz) δ 7.56-

7.38 (c, 5 H), 4.37 (s, 2 H), 3.87-3.69 (c, 4 H), 3.44-3.32 (c, 4

H); MS (CI/NH₃) 219 (MH⁺).

K₂CO₃Meth od . (R)-1-[4-(4-Oxa zolo[5,4-c]p yr id in -2-yl-

p ip er a zin -1-yl)p yr im id in -2-yl]eth a n ol (67: R¹) Oxa zolo-

[5,4-c]p yr id in -2-yl). To a solution of butyrate 36l (3.27 g, 8.24

mmol) in MeOH (82 mL) was added K₂CO₃(2.28 g, 16.5 mmol).

This mixture was stirred at room temperature for 4 h,

quenched with saturated aqueous NH₄Cl (0.88 g, 16.5 mmol),

and evaporated. The residue was diluted with saturated

aqueous NaHCO₃and extracted with CHCl₃(5×). The com-

bined organic extracts were dried (Na₂SO₄), filtered, evapo-

rated, and purified by flash column chromatography (5%

MeOH/CHCl₃) to give 2.42 g (90%) of compound 67 as a white

solid. mp 181-183 °C; [R]_D+15.3 (c 0.5, MeOH); ¹H NMR

(CDCl₃, 300 MHz) δ 8.54 (d, J ) 0.5 Hz, 1 H), 8.35 (d, J ) 5.3

Hz, 1 H), 8.25 (d, J ) 6.2 Hz, 1 H), 7.27 (dd, J ) 5.3, 0.7 Hz,

1 H), 6.44 (d, J ) 6.2 Hz, 1 H), 4.71 (q, J ) 6.6 Hz, 1 H), 4.25

(br s, 1 H), 3.86-3.83 (c, 8 H), 1.50 (d, J ) 6.6 Hz, 3 H); MS

(CI/NH₃) 327 (MH⁺). Anal. (C₁₆H₁₈N₆O₂) C, H, N.

(R)-4-[2-(1-Acetoxy-eth yl)p yr im id in -4-yl]p ip er a zin e-1-

ca r boxa m id in e Bis(tr iflu or oa ceta te) Sa lt (49). Prepared

from bis(Boc)-guanidine 48, to give compound 49 (76%) as a

white solid. ¹H NMR (CD₃OD, 250 MHz) δ 8.23 (d, J ) 6.2

Hz, 1 H), 7.04 (d, J ) 6.2 Hz, 1 H), 5.68 (q, J ) 6.8 Hz, 1 H),

4.14-4.03 (c, 4 H), 3.78-3.69 (c, 4 H), 2.16 (s, 3 H), 1.63 (d, J

) 6.8 Hz, 3 H); MS (TS) 293 (MH⁺).

Gen er a l P r oced u r e J . P r ep a r a tion of Com p ou n d s

47a -d , 63, a n d 64 by Con d en sa tion of Gu a n id in e Bis-

(tr iflu or oa ceta te) Sa lts 45 a n d 49 w ith Dica r bon yls/

Dica r bon yl Equ iva len ts 46a -f. Representative experimen-

tal procedures for 47a , 63, and 64 are given below.

2-(4-Ben zyl-piper azin -1-yl)-4,6-bis-tr iflu or om eth yl-pyr -

im id in e (47a : R ) R′ ) Tr iflu or om eth yl). To a solution of

i-PrONa/ i-PrOH [freshly prepared by refluxing sodium metal

(195 mg, 8.50 mmol, washed with hexanes) in freshly distilled

522 J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 2

Chu-Moyer et al.

(R)-1-{4-[4-(4,6-Dim et h yl-p yr im id in -2-yl)p ip er a zin -1-

yl]p yr im id in -2-yl}eth a n ol (50: R¹) 4,6-Dim eth yl-p yr im i-

d in -2-yl). Prepared from acetate 39a (LiOH method) and

purified by flash column chromatography (CHCl₃f 1% MeOH/

CHCl₃) to give compound 50 (100%) as a slightly yellow solid.

(R)-1-[4-(4-Qu in olin -2-yl-p ip er a zin -1-yl)p yr im id in -2-yl]-

eth a n ol (57: R¹) Qu in olin -2-yl). Prepared from acetate 36d

(LiOH method) and purified by flash column chromatography

(0.5% MeOH/CHCl₃) to give compound 57 (54%) as a white

foam. [R]_D+17.4 (c 1.0, MeOH); ¹H NMR (CDCl₃, 300 MHz) δ

8.23 (d, J ) 6.1 Hz, 1 H), 7.94 (d, J ) 9.1 Hz, 1 H), 7.73 (d, J

) 8.4 Hz, 1 H), 7.62 (d, J ) 7.8 Hz, 1 H), 7.56 (t, J ) 6.1 Hz,

1 H), 7.25 (t, J ) 8.4 Hz, 1 H), 6.99 (d, J ) 9.1 Hz, 1 H), 6.42

(d, J ) 6.1 Hz, 1 H), 4.73 (q, J ) 6.6 Hz, 1 H), 3.88-3.85 (c, 8

H), 1.53 (d, J ) 6.6 Hz, 3 H); MS (APCI) 336 (MH⁺). Anal.

(C₁₉H₂₁N₅O‚1.25H₂O) C, H, N.

1

mp 132-133 °C; [R]_D+16.6 (c 1.3, MeOH); H NMR (CDCl₃,

300 MHz) δ 8.20 (d, J ) 6.2 Hz, 1 H), 6.40 (d, J ) 6.2 Hz, 1

H), 6.31 (s, 1 H), 4.73 (q, J ) 6.6 Hz, 1 H), 4.36 (br s, 1 H),

3.99-3.91 (c, 4 H), 3.81-3.72 (c, 4 H), 2.29 (s, 6 H), 1.50 (d, J

) 6.6 Hz, 3 H); MS (CI/NH₃) 315 (MH⁺). Anal. (C₁₆H₂₂N₆O) C,

H, N.

(R)-1-{4-[4-(2,6-Dim et h yl-p yr im id in -4-yl)p ip er a zin -1-

yl]p yr im id in -2-yl}eth a n ol (51: R¹) 2,6-Dim eth yl-p yr im -

id in -4-yl). Prepared from acetate 39b (LiOH method) and

purified by flash column chromatography (5% MeOH/CHCl₃)

to give compound 51 (78%) as a white solid. mp 125.5-127

°C; [R]_D+17.3 (c 1.0, MeOH); ¹H NMR (CDCl₃, 250 MHz) δ

8.25 (d, J ) 6.2 Hz, 1 H), 6.41 (d, J ) 6.2 Hz, 1 H), 6.21 (s, 1

H), 4.74 (m, 1 H), 4.30 (d, J ) 4.4 Hz, 1 H), 3.85-3.80 (c, 8 H),

2.52 (s, 3 H), 2.36 (s, 3 H), 1.53 (d, J ) 6.8 Hz, 3 H); MS (APCI)

315 (MH⁺). Anal. (C₁₆H₂₂N₆O‚0.25H₂O) C, H, N.

(R)-1-{4-[4-(4-Meth yl-pyr im idin -2-yl)piper azin -1-yl]pyr -

im id in -2-yl}eth a n ol (58: R¹) 4-Meth yl-p yr im id in -2-yl).

Prepared from a 1:1 mixture of acetate 39d and desired

compound 58 (LiOH method) and purified by flash column

chromatography (1% MeOH/CHCl₃) to give compound 58 (25%

for 2 steps from 37a ) as a white solid. mp 116-117.5 °C; [R]_D

1

+14.9 (c 1.2, MeOH); H NMR (CDCl₃, 250 MHz) δ 8.20 (d, J

) 6.3 Hz, 1 H), 8.18 (d, J ) 5.0 Hz, 1 H), 6.45-6.35 (c, 2 H),

4.71 (q, J ) 6.6 Hz, 1 H), 4.68 (br s, 1 H), 3.98-3.87 (c, 4 H),

3.80-3.67 (c, 4 H), 2.34 (s, 3 H), 1.51 (d, J ) 6.6 Hz, 3 H); MS

(APCI) 301 (MH⁺). Anal. (C₁₅H₂₀N₆O) C, H, N.

1R-(4-{4-[2-(1R-Hydr oxyeth yl)pyr im idin -4-yl]piper azin -

1-yl}p yr im id in -2-yl)eth a n ol (52: R¹) (R)-2-(1-Hyd r oxy-

eth yl)p yr im id in -4-yl). Prepared from dibutyrate 40 (LiOH

method, 3:1 MeOH/H₂O) and purified by tritration (EtOAc) to

give compound 52 (76%) as a white solid. mp 158-160 °C; [R]_D

(R)-1-{4-[4-(4,6-Bis-tr iflu or om eth yl-p yr im id in -2-yl)p ip -

er a zin -1-yl]p yr im id in -2-yl}eth a n ol (59: R¹) 4,6-Bis-

tr iflu or om eth yl-p yr im id in -2-yl). Prepared from acetate 36e

(LiOH method) and purified by flash column chromatography

(CHCl₃f 1% MeOH/CHCl₃) to give compound 59 (96%) as a

pale yellow solid. mp 156.5-158 °C; [R]_D+12.2 (c 1.4, MeOH);

¹H NMR (CDCl₃, 300 MHz) δ 8.23 (d, J ) 6.2 Hz, 1 H), 7.03

(s, 1 H), 6.42 (d, J ) 6.2 Hz, 1 H), 4.69 (q, J ) 6.6 Hz, 1 H),

4.11-3.93 (c, 4 H), 3.89-3.70 (c, 4 H), 1.49 (d, J ) 6.7 Hz, 3

H); MS (APCI) 423 (MH⁺). Anal. (C₁₆H₁₆F₆N₆O) C, H, N.

(R)-1-{4-[4-(4,6-Dieth yl-p yr im id in -2-yl)p ip er a zin -1-yl]-

p yr im id in -2-yl}eth a n ol (60: R¹) 4,6-Dieth yl-p yr im id in -

2-yl). Prepared from acetate 36f (LiOH method) and purified

by flash column chromatography (CHCl₃f 2.5% MeOH/

CHCl₃) to give compound 60 (75%) as a yellow solid. mp 104-

105 °C; [R]_D+17.0 (c 0.7, MeOH); ¹H NMR (CDCl₃, 300 MHz)

δ 8.18 (d, J ) 6.2 Hz, 1 H), 6.39 (d, J ) 6.2 Hz, 1 H), 6.30 (s,

1 H), 4.39 (m, 1 H), 4.38 (br s, 1 H), 4.01-3.91 (c, 4 H), 3.82-

3.68 (c, 4 H), 2.56 (q, J ) 7.6 Hz, 4 H), 1.49 (d, J ) 6.6 Hz, 3

H), 1.22 (t, J ) 7.7 Hz, 6 H); MS (CI/NH₃) 343 (MH⁺). Anal.

(C₁₈H₂₆N₆O‚0.25H₂O) C, H, N.

1

+32.4 (c 0.9, MeOH); H NMR (CDCl₃, 400 MHz) δ 8.26 (d, J

) 6.0 Hz, 2 H), 6.40 (d, J ) 6.2 Hz, 2 H), 4.71 (m, 2 H), 4.27

(m, 2 H), 3.90-3.70 (c, 8 H), 1.51 (d, J ) 6.8 Hz, 6 H); MS

(APCI) 331 (MH⁺). Anal. (C₁₆H₂₂N₆O₂) C, H, N.

(R)-1-[4-(4-Ben zoxa zol-2-yl-p ip er a zin -1-yl)p yr im id in -

2-yl]eth a n ol (53: R¹) Ben zoxa zol-2-yl). Prepared from

acetate 39c (LiOH method) and purified by flash column

chromatography (3% MeOH/CHCl₃) to give compound 53 (77%)

as a white solid. mp 139-141 °C; [R]_D+14.4 (c 0.5, MeOH);

¹H NMR (CDCl₃, 250 MHz) δ 8.26 (d, J ) 6.2 Hz, 1 H), 7.38

(dd, J ) 7.8, 0.7 Hz, 1 H), 7.30 (dd, J ) 7.8, 0.5 Hz, 1 H), 7.19

(td, 7.6, 1.2 Hz, 1 H), 7.06 (td, J ) 7.6, 1.2 Hz, 1 H), 6.46 (d,

J ) 6.2 Hz, 1 H), 4.74 (q, J ) 6.6 Hz, 1 H), 4.29 (br s, 1 H),

3.90-3.74 (c, 8 H), 1.53 (d, J ) 6.6 Hz, 3 H); MS (CI/NH₃) 326

(MH⁺). Anal. (C₁₇H₁₉N₅O₂‚0.5H₂O) C, H, N.

(R)-1-[4-(4-Ben zo[d ]isoth ia zol-3-yl-p ip er a zin -1-yl)p yr -

im id in -2-yl]eth a n ol (54: R¹) Ben zo[d ]isoth ia zol-3-yl).

Prepared from acetate 36a (LiOH method) and purified by

flash column chromatography (4% MeOH/CHCl₃) to give

compound 54 (80%) as a white foam. [R]_D+16.2 (c 1.2, MeOH);

¹H NMR (CDCl₃, 250 MHz) δ 8.25 (d, J ) 6.2 Hz, 1 H), 7.94

(dd, J ) 8.1, 1.0 Hz, 1 H), 7.85 (dd, J ) 8.1, 1.0 Hz, 1 H), 7.51

(td, J ) 7.5, 1.1 Hz, 1 H), 7.41 (td, J ) 7.5, 1.1 Hz, 1 H), 6.47

(d, J ) 6.2 Hz, 1 H), 4.75 (q, J ) 6.6 Hz, 1 H), 3.94-3.89 (c, 4

H), 3.67-3.63 (c, 4 H), 1.54 (d, J ) 6.6 Hz, 3 H); MS (APCI)

342 (MH⁺). Anal. (C₁₇H₁₉N₅OS) C, H, N.

(R)-1-{4-[4-(4,6-Diisop r op yl-p yr im id in -2-yl)p ip er a zin -

1-yl]p yr im id in -2-yl}eth a n ol (61: R¹) 4,6-Diisop r op yl-

p yr im id in -2-yl). Prepared from acetate 36g (LiOH method)

and purified by flash column chromatography (5% MeOH/

CHCl₃) to give compound 61 (85%) as a slightly yellow solid.

1

mp 82-83.5 °C; [R]_D+14.5 (c 1.7, MeOH); H NMR (CDCl₃,

300 MHz) δ 8.22 (d, J ) 6.2 Hz, 1 H), 6.42 (d, J ) 6.2 Hz, 1

H), 6.33 (s, 1 H), 4.75 (m, 1 H), 4.38 (m, 1 H), 4.03-3.94 (c, 4

H), 3.81-3.72 (c, 4 H), 2.80 (septet, J ) 6.9 Hz, 2 H), 1.53 (d,

J ) 6.6 Hz, 3 H), 1.24 (d, J ) 6.9 Hz, 12 H). MS (CI/NH₃):

371 (MH⁺); MS (CI/NH₃) 371 (MH⁺). Anal. (C₂₀H₃₀N₆O) C, H,

N.

(R)-1-[4-(4-Ben zo[d ]isoxa zol-3-yl-p ip er a zin -1-yl)p yr -

im id in -2-yl]eth a n ol (55: R¹) Ben zo[d ]isoxa zol-3-yl).

Prepared from acetate 36b (LiOH method) and purified by

flash column chromatography (1% MeOH/CHCl₃) to give

compound 55 (70%) as a white solid. mp 129-131 °C; [R]_D

(R)-1-{4-[4-(4-H yd r oxym et h yl-6-m et h yl-p yr im id in -2-

yl)p ip er a zin -1-yl]p yr im id in -2-yl}eth a n ol (62: R¹) 4-Hy-

d r oxym eth yl-6-m eth yl-p yr im id in -2-yl). Prepared from ace-

tate 36i (LiOH method) and purified by tritration (i-PrOH) to

give compound 62 (83%) as a white solid. mp 139-140 °C; [R]_D

1

+23.0 (c 1.0, MeOH); H NMR (CDCl₃, 250 MHz) δ 8.25 (d, J

) 6.2 Hz, 1 H), 7.72 (d, J ) 8.0 Hz, 1 H), 7.53-7.46 (c, 2 H),

7.25 (m, 1 H), 6.47 (d, J ) 6.2 Hz, 1 H), 4.75 (q, J ) 6.6 Hz, 1

H), 4.30 (br s, 1 H), 3.93-3.88 (c, 4 H), 3.67-3.63 (c, 4 H),

1.54 (d, J ) 6.7 Hz, 3 H); MS (APCI) 326 (MH⁺). Anal.

(C₁₇H₁₉N₅O₂‚0.25H₂O) C, H, N.

1

+21.6 (c 2.0, MeOH); H NMR (CDCl₃, 300 MHz) δ 8.21 (d, J

) 6.1 Hz, 1 H), 6.41 (d, J ) 6.2 Hz, 1 H), 6.37 (s, 1 H), 4.71 (m,

1 H), 4.54 (s, 2 H), 4.32 (d, J ) 4.7 Hz, 1 H), 4.02-3.93 (c, 4

H), 3.78-3.68 (c, 4 H), 3.65 (br s, 1 H), 2.34 (s, 3 H), 1.51 (d,

J ) 6.6 Hz, 3 H); MS (TS) 331 (MH⁺). Anal. (C₁₆H₂₂N₆O₂) C,

H, N.

(R)-1-[4-(4-Isoqu in olin -1-yl-p ip er a zin -1-yl)p yr im id in -

2-yl]eth a n ol (56: R¹) Isoqu in olin -1-yl). Prepared from

acetate 36c (LiOH method) and purified by flash column

chromatography (3% MeOH/CHCl₃) to give compound 56 (54%)

as a colorless gum. [R]_D+16.7 (c 1.4, MeOH); ¹H NMR (CDCl₃,

250 MHz) δ 8.25 (d, J ) 6.2 Hz, 1 H), 8.18-8.13 (c, 2 H), 7.80

(d, J ) 7.7 Hz, 1 H), 7.65 (td, J ) 8.0, 1.2 Hz, 1 H), 7.56 (td,

J ) 8.0, 1.2 Hz, 1 H), 7.32 (d, J ) 5.7 Hz, 1 H), 6.48 (d, J ) 6.2

Hz, 1 H), 4.75 (q, J ) 6.6 Hz, 1 H), 4.48 (br s, 1 H), 3.96-3.92

(c, 4 H), 3.54-3.52 (c, 4 H), 1.54 (d, J ) 6.6 Hz, 3 H); MS (APCI)

336 (MH⁺). Anal. (C₁₉H₂₁N₅O‚0.5H₂O) C, H, N.

(R)-1-[4-(4-Oxa zolo[4,5-c]p yr id in -2-yl-p ip er a zin -1-yl)-

p yr im id in -2-yl]eth a n ol (66: R¹) Oxa zolo[4,5-c]p yr id in -

2-yl). Prepared from butyrate 36k (LiOH method) and purified

by flash column chromatography (2 f 5% MeOH/CHCl₃) to

give compound 66 (37%) as a white solid. mp 178-180 °C; [R]_D

1

+17.1 (c 1.1, MeOH); H NMR (CDCl₃, 250 MHz) δ 8.69 (s, 1

H), 8.34 (d, J ) 5.3 Hz, 1 H), 8.27 (d, J ) 6.1 Hz, 1 H), 7.27 (d,

J ) 5.3 Hz, 1 H), 6.46 (d, J ) 6.1 Hz, 1 H), 4.74 (q, J ) 6.6 Hz,

Sorbitol Dehydrogenase Inhibitors

J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 2 523

1 H), 3.87-3.83 (c, 8 H), 1.52 (d, J ) 6.6 Hz, 3 H); MS (TS)

327 (MH⁺). Anal. (C₁₆H₁₈N₆O₂‚0.25H₂O) C, H, N.

(130 mL) dropwise via an addition funnel over 50 min, keeping

the internal temperature below 10 °C. After 15 min, the ice

bath was removed and the reaction mixture was quenched

with water. The layers were separated, and the aqueous phase

was further extracted with CH₂Cl₂(3×). The combined organic

extracts were washed with saturated aqueous NaHCO₃(2×)

and H₂O (1×), dried (Na₂SO₄), filtered, and evaporated to give

85 g (crude, >100%) of triflate 34d as a dark oil, which was

used immediately in the next reaction without further puri-

(R)-1-[4-(4-Oxa zolo[5,4-b]p yr id in -2-yl-p ip er a zin -1-yl)-

p yr im id in -2-yl]eth a n ol (68: R ¹) Oxa zolo[5,4-b]p yr id in -

2-yl). Prepared from butyrate 36m (LiOH method) and

purified by flash column chromatography (2% MeOH/CHCl₃)

to give compound 68 (80%) as a white solid. mp 153-156 °C;

1

[R]_D+16.1 (c 1.0, MeOH); H NMR (CDCl₃, 300 MHz) δ 8.25

(d, J ) 6.2 Hz, 1 H), 7.95 (dd, J ) 5.1, 1.5 Hz, 1 H), 7.58 (dd,

J ) 7.7, 1.5 Hz, 1 H), 7.15 (dd, J ) 7.7, 5.1 Hz, 1 H), 6.45 (d,

J ) 6.2 Hz, 1 H), 4.72 (q, J ) 6.6 Hz, 1 H), 4.25 (br s, 1 H),

3.85-3.82 (c, 8 H), 1.51 (d, J ) 6.6 Hz, 3 H); MS (CI/NH₃) 327

(MH⁺). Anal. (C₁₆H₁₈N₆O₂) C, H, N.

1

fication. H NMR (CDCl₃, 400 MHz) δ 8.83 (d, J ) 5.4 Hz, 1

H), 7.03 (d, J ) 5.6 Hz, 1 H), 5.82 (q, J ) 6.8 Hz, 1 H), 2.41-

2.32 (c, 2 H), 1.72-1.60 (c, 2 H), 1.62 (d, J ) 6.8 Hz, 3 H), 0.95

(t, J ) 7.5 Hz, 3 H); MS (APCI) 343 (MH⁺).

A mixture of triflate 34d (0.25 mol, theory) and cis-1-benzyl-

3,5-dimethyl-piperazine¹⁹(72a , 101 g, 0.50 mol) in CH₃CN (310

mL) was heated at reflux for 15 h, concentrated, and purified

by flash column chromatography (15% EtOAc/hexanes) to give

52 g (53%) of compound 73a as an orange oil. ¹H NMR and

MS data as above. HPLC (Chiralpak AD, 90:10 hexane/i-PrOH

+0.1% DEA, 1 mL/min) 6.17 min (93.5 area %), 9.31 min (6.5

area %).

Compound 73a (131 g, 79% ee) was purified by chiral HPLC

under the following conditions (column: 15 cm id × 25 cm Pro-

chrom column packed with Chiracel AD; mobile phase: 90:10

n-heptane/i-PrOH; flow rate: ∼1 L/min; loading: 4.2 g/cycle)

to provide the (R)-enantiomer (109 g, >98% ee) as a yellow oil.

(R)-1-[4-(Qu in oxa lin -2-yl-p ip er a zin -1-yl)p yr im id in -2-

yl]eth a n ol (69: R¹) Qu in oxa lin -2-yl). Prepared from

acetate 36n (LiOH method) and purified by flash column

chromatography (2×; 2% MeOH/CHCl₃) followed by tritration

(hexanes) to give compound 69 (90%) as a pale yellow solid.

1

mp 106-108 °C; [R]_D+16.6 (c 1.0, MeOH); H NMR (CDCl₃,

250 MHz) δ 8.62 (s, 1 H), 8.26 (d, J ) 6.1 Hz, 1 H), 7.92 (dd,

J ) 8.2, 1.0 Hz, 1 H), 7.72 (dd, J ) 8.3, 1.1 Hz, 1 H), 7.61 (td,

J ) 8.4, 1.4 Hz, 1 H), 7.44 (td, J ) 8.1, 1.5 Hz, 1 H), 6.45 (d,

J ) 6.2 Hz, 1 H), 4.75 (m, 1 H), 4.32 (br s, 1 H), 3.95-3.85 (c,

8 H), 1.54 (d, J ) 6.8 Hz, 3 H); MS (CI/NH₃) 337 (MH⁺). Anal.

(C₁₈H₂₀N₆O) C, H, N.

(R)-1-{4-[4-(3-Met h yl-q u in oxa lin -2-yl)p ip er a zin -1-yl]-

p yr im id in -2-yl}eth a n ol (70: R¹) 3-Meth yl-qu in oxa lin -

2-yl). Prepared from acetate 36o (LiOH method) and purified

by flash column chromatography (1% MeOH/CHCl₃) to give

compound 70 (88%) as a yellow solid. mp 145-147 °C; [R]_D

1R-[4-(4-Ben zyl-2S-m eth yl-p ip er a zin -1-yl)p yr im id in -2-

yl]eth yl Bu tyr a te (73b). A mixture of chloropyrimidine 34c

(1.83 g, 8.0 mmol), (S)-1-benzyl-3-methyl-piperazine²⁰(72b ,

1.52 g, 8.0 mmol), and i-Pr₂NEt (2.78 mL, 16.0 mmol) in

n-BuOH (20 mL) was allowed to stir at reflux for 22 h, cooled

to room temperature, and concentrated. The residue was

diluted with saturated aqueous NaHCO₃and extracted with

CHCl₃(3×). The combined organic extracts were dried (Na₂SO₄),

filtered, evaporated, and purified by flash column chromatog-

raphy (1:4 f 2:1 EtOAc/hexanes) to give 2.12 g (69%) of

1

+13.7 (c 0.9, MeOH); H NMR (CDCl₃, 250 MHz) δ 8.25 (d, J

) 6.1 Hz, 1 H), 7.92 (d, J ) 7.7 Hz, 1 H), 7.83 (d, J ) 7.7 Hz,

1 H), 7.63-7.52 (c, 2 H), 6.47 (d, J ) 6.1 Hz, 1 H), 4.74 (q, J

) 6.6 Hz, 1 H), 3.95-3.85 (c, 4 H), 3.55-3.45 (c, 4 H), 2.76 (s,

3 H), 1.54 (d, J ) 6.6 Hz, 3 H); MS (APCI) 351 (MH⁺). Anal.

(C₁₉H₂₂N₆O‚0.5H₂O) C, N; H: calcd, 6.45; found, 6.04.

1

compound 73b as a yellow oil. H NMR (CDCl₃, 400 MHz) δ

(R)-1-{4-[4-(6,7-Dich lor o-q u in oxa lin -2-yl)p ip er a zin -1-

yl]p yr im id in -2-yl}eth a n ol (71: R¹) 6,7-Dich lor o-qu in -

oxa lin -2-yl). To a solution of amino-alcohol 37b (60 mg, 0.29

mmol) in i-PrOH (6 mL) was added Et₃N (0.12 mL, 0.86 mmol)

followed by 2,6,7-trichloroquinoxaline³²(81 mg, 0.35 mmol).

This mixture was heated to reflux for 4 h, cooled to room

temperature, and evaporated. The residue was diluted with

saturated aqueous NaHCO₃and extracted with CHCl₃(2×)

followed by 10% i-PrOH/CHCl₃(3×). The combined organic

extracts were dried (Na₂SO₄), filtered, evaporated, and purified

by flash column chromatography (2% MeOH/CHCl₃) followed

by tritration (hexanes) to give compound 71 (52%) as a yellow

solid. mp 143-145 °C; [R]_D+13.4 (c 0.9, MeOH); ¹H NMR

(CDCl₃, 300 MHz) δ 8.55 (s, 1 H), 8.25 (d, J ) 6.1 Hz, 1 H),

7.96 (s, 1 H), 7.78 (s, 1 H), 6.42 (d, J ) 6.1 Hz, 1 H), 4.72 (q,

J ) 6.6 Hz, 1 H), 4.28 (br s, 1 H), 3.95-3.85 (c, 8 H), 1.51 (d,

8.15 (d, J ) 6.2 Hz, 1 H), 7.34-7.23 (c, 5 H), 6.28 (d, J ) 6.2

Hz, 1 H), 5.66 (q, J ) 6.6 Hz, 1 H), 4.40 (m, 1 H), 4.17 (m, 1

H), 3.57 (d, J ) 13.3 Hz, 1 H), 3.43 (d, J ) 13.3 Hz, 1 H), 3.13

(td, J ) 12.8, 3.5 Hz, 1 H), 2.89 (d, J ) 11.2 Hz, 1 H), 2.71 (d,

J ) 11.2 Hz, 1 H), 2.36 (t, J ) 7.4 Hz, 2 H), 2.19 (dd, J ) 11.2,

3.8 Hz, 1 H), 2.09 (td, J ) 12.1, 3.6 Hz, 1 H), 1.71-1.61 (c, 2

H), 1.55 (d, J ) 6.6 Hz, 3 H), 1.26 (d, J ) 6.8 Hz, 3 H), 0.93 (t,

J ) 7.5 Hz, 3 H); MS (APCI) 383 (MH⁺).

1R-[4-(4-Ben zyl-2R-m eth yl-p ip er a zin -1-yl)p yr im id in -2-

yl]eth yl Bu tyr a te (73c). Prepared from (R)-1-benzyl-3-meth-

yl-piperazine,²⁰following the procedure for 73b, and was

purified by flash column chromatography (1:4 f 2:1 EtOAc/

hexanes) to give compound 73c (65%) as a yellow oil. ¹H NMR

(CDCl₃, 400 MHz) δ 8.14 (d, J ) 6.2 Hz, 1 H), 7.34-7.23 (c, 5

H), 6.26 (d, J ) 6.2 Hz, 1 H), 5.65 (q, J ) 6.6 Hz, 1 H), 4.46

(m, 1 H), 4.10 (m, 1 H), 3.56 (d, J ) 13.3 Hz, 1 H), 3.42 (d, J

) 13.3 Hz, 1 H), 3.15 (m, 1 H), 2.88 (d, J ) 11.2 Hz, 1 H), 2.70

(d, J ) 11.2 Hz, 1 H), 2.36 (t, J ) 7.4 Hz, 2 H), 2.19 (m, 1 H),

2.08 (m, 1 H), 1.70-1.60 (c, 2 H), 1.54 (d, J ) 6.8 Hz, 3 H),

1.23 (d, J ) 6.8 Hz, 3 H), 0.93 (t, J ) 7.4 Hz, 3 H); MS (APCI)

383 (MH⁺).

J ) 6.6 Hz, 3 H); MS (TS) 405, 407 (MH⁺). Anal. (C₁₈H₁₈

Cl₂N₆O‚0.25H₂O) C, H, N.

-

1R-[4-(4-Ben zyl-2R,6S-d im eth yl-p ip er a zin -1-yl)p yr im i-

d in -2-yl]eth yl Bu tyr a te (73a ). F r om Ch lor op yr im id in e

34c. A mixture of chloropyrimidine 34c (1.00 g, 4.38 mmol)

and cis-1-benzyl-3,5-dimethyl-piperazine¹⁹(72a , 3.57 g, 17.5

mmol) was heated at 150-155 °C for 24 h, cooled to room

temperature, and purified by flash column chromatography

(1:4 f 1:1 EtOAc/hexanes) to give 1.00 g (58%) of compound

Gen er a l P r oced u r e L. P r ep a r a tion of Com p ou n d s

74a -c by Deben zyla tion of Com p ou n d s 73a -c. A repre-

sentative experimental procedure for 74a is given below.

1

73a as an orange oil. H NMR (CDCl₃, 400 MHz) δ 8.15 (d, J

1R-[4-(2R,6S-Dim eth yl-p ip er a zin -1-yl)p yr im id in -2-yl]-

eth yl Bu tyr a te (74a ). To a solution of benzyl compound 73a

(4.85 g, 12.2 mmol) in MeOH (20 mL) was added HCl (5 M in

MeOH, 2.6 mL, 12.9 mmol). After 5 min, HCO₂NH₄(7.70 g,

122 mmol) was added followed by a slurry of 10% Pd/C (0.73

g, 15 wt %) in MeOH (41 mL). This mixture was stirred at

reflux for 1 h and an additional portion of 10% Pd/C (0.1 g)

was added. After 30 min, this mixture was cooled to room

temperature and filtered through Celite. The filtrate was

concentrated, diluted with saturated aqueous NaHCO₃, and

extracted with 10% i-PrOH/CHCl₃(2×). The combined organic

extracts were dried (Na₂SO₄), filtered, and evaporated to give

3.54 g (95%) of compound 74a as a yellow oil, which was

) 6.2 Hz, 1 H), 7.39-7.24 (c, 5 H), 6.25 (d, J ) 6.2 Hz, 1 H),

5.66 (q, J ) 6.6 Hz, 1 H), 4.45 (m, 1 H), 4.24 (m, 1 H), 3.52 (s,

2 H), 2.73 (d, J ) 11.2 Hz, 2 H), 2.37 (t, J ) 7.4 Hz, 2 H), 2.22

(d, J ) 10.5 Hz, 2 H), 1.70-1.60 (c, 2 H), 1.55 (d, J ) 6.8 Hz,

3 H), 1.30 (d, J ) 6.6 Hz, 3 H), 1.27 (d, J ) 6.8 Hz, 3 H), 0.93

(t, J ) 7.5 Hz, 3 H); MS (APCI) 397 (MH⁺); HPLC (Chiralpak

AD, 90:10 hexane/i-PrOH +0.1% DEA, 1 mL/min) 6.00 min

(89.6 area %), 8.87 min (10.4 area %).

F r om Tr ifla te 34d . To a solution of (R)-1-(4-hydroxy-

pyrimidin-2-yl)ethyl butyrate¹³(52 g, 0.25 mol) and Et₃N (36.2

mL, 0.26 mol) in CH₂Cl₂(700 mL) at 0 °C with stirring under

N₂was added a solution of Tf₂O (44 mL, 0.260 mol) in CH₂Cl₂

524 J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 2

Chu-Moyer et al.

sufficiently pure to carry on to the next step. ¹H NMR (CDCl₃,

400 MHz) δ 8.15 (d, J ) 6.2 Hz, 1 H), 6.25 (d, J ) 6.2 Hz, 1

H), 5.66 (q, J ) 6.6 Hz, 1 H), 4.39 (m, 1 H), 4.22 (m, 1 H),

2.95-2.88 (c, 4 H), 2.36 (t, J ) 7.5 Hz, 2 H), 1.71-1.62 (c, 2

H), 1.55 (d, J ) 6.8 Hz, 3 H), 1.26 (d, J ) 7.1 Hz, 3 H), 1.23 (d,

J ) 6.9 Hz, 3 H), 0.93 (t, J ) 7.3 Hz, 3 H); MS (APCI) 307

(MH⁺).

J ) 11.2, 3.7 Hz, 1 H), 2.13 (m, 1 H), 1.48 (s, 9 H), 1.44 (s, 9

H), 1.34 (d, J ) 6.7 Hz, 3 H); MS (APCI) 433 (MH⁺).

4-[2-(1R-Bu t yr yloxy-et h yl)p yr im id in -4-yl]-2R,6S-p ip -

er azin e-1-car boxam idin e Bis(tr iflu or oacetate) Salt (80a).

Prepared from bis(Boc)-guanidine 79a (general procedure I)

to give compound 80a (crude, >100%) as a yellow oil that was

used directly in the next reaction. ¹H NMR (CD₃OD, 300 MHz)

δ 8.26 (d, J ) 6.2 Hz, 1 H), 7.24 (d, J ) 6.2 Hz, 1 H), 5.70 (q,

J ) 6.8 Hz, 1 H), 4.31-4.19 (c, 2 H), 3.67-3.55 (c, 2 H), 3.45-

3.36 (c, 2 H), 2.45 (t, J ) 7.4 Hz, 2 H), 1.73-1.61 (c, 5 H),

1.35-1.27 (c, 6 H), 0.97 (t, J ) 7.3 Hz, 3 H); MS (CI/NH₃) 349

(MH⁺).

Gen er a l P r oced u r e M. P r ep a r a tion of Com p ou n d s

76a -h by Rea ction of P ip er a zin o-p yr im id in es 74a -c

w ith Activa ted Heter ocycles 34c a n d 75a -c. Representa-

tive experimental procedures for 76b,c are given below.

Reflu xin g i-P r OH/n -Bu OH Meth od . 1R-(4-{4-[2-(1R-

Bu tyr yloxy-eth yl)p yr im id in -4-yl]-2R,6S-d im eth yl-p ip er -

a zin -1-yl}p yr im id in -2-yl)eth yl Bu tyr a te (76b: R¹) (R)-

2-(1-Bu tyr yloxy-eth yl)p yr im id in -4-yl, R²) R⁶) â-Me). A

mixture of piperazino-pyrimdine 74a (0.30 g, 0.98 mmol),

chloropyrimidine 34c (0.22 g, 0.98 mmol), and Et₃N (0.27 mL,

1.96 mmol) in i-PrOH (5 mL) was allowed to stir at reflux for

18 h, cooled to room temperature, concentrated, and purified

by flash column chromatography (1 f 3% MeOH/CHCl₃) to

give 0.47 g (96%) of compound 76b as a yellow oil. ¹H NMR

(CDCl₃, 400 MHz) δ 8.21 (d, J ) 6.0 Hz, 2 H), 6.41 (d, J ) 6.2

Hz, 1 H), 6.31 (d, J ) 6.2 Hz, 1 H), 5.69 (q, J ) 6.8 Hz, 2 H),

4.72-4.24 (c, 4 H), 3.24-3.21 (c, 2 H), 2.38 (t, J ) 7.5 Hz, 4

H), 1.72-1.62 (c, 4 H), 1.56 (d, J ) 6.8 Hz, 6 H), 1.28-1.13 (c,

6 H), 0.95 (t, J ) 7.5 Hz, 6 H); MS (APCI) 499 (MH⁺).

(R)-4-Ben zyl-2-m eth yl-piper azin e-1-car boxam idin e Bis-

(tr iflu or oa ceta te) Sa lt (80b). Prepared from bis(Boc)-guani-

dine 79b (general procedure I) to give compound 80b (crude,

>100%) as a white solid that was used directly in the next

reaction. ¹H NMR (CD₃OD, 400 MHz) δ 7.53-7.43 (c, 5 H),

4.39-4.30 (c, 3 H), 3.92 (m, 1 H), 3.59 (m, 1 H), 3.52 (m, 1 H),

3.40 (m, 1 H), 3.30 (m, 1 H), 3.13 (m, 1 H), 1.39 (d, J ) 6.0 Hz,

3 H); MS (CI/NH₃) 233 (MH⁺).

1R-{4-[4-(4-Meth oxym eth yl-6-m eth yl-p yr im id in -2-yl)-

3R,5S-d im et h yl-p ip er a zin -1-yl]p yr im id in -2-yl}et h a n ol

(81a ). Prepared from guanidine bis(trifluoroacetate) salt 80a

and 1-methoxy-2,4-pentanedione³³(46d ) (general procedure J )

and purified by flash column chromatography (1 f 2% MeOH/

1

CHCl₃) to give compound 81a (77%) as a yellow oil. H NMR

Nea t Meth od . 1R-[4-(2R,6S-Dim eth yl-4-oxa zolo[5,4-c]-

pyr idin -2-yl-piper azin -1-yl)pyr im idin -2-yl]eth yl Bu tyr ate

(76c: R¹) Oxa zolo[5,4-c]p yr id in -2-yl, R²) R⁶) â-Me).

A mixture of piperazino-pyrimidine 74a (0.10 g, 0.33 mmol)

and 2-methylthio-oxazolo[5,4-c]pyridine²⁸(75a , 0.11 g, 0.66

mmol) was heated at 120 °C for 7 h. The residue was purified

by flash column chromatography (1% MeOH/CHCl₃) to give

(CDCl₃, 400 MHz) δ 8.16 (d, J ) 6.2 Hz, 1 H), 6.54 (s, 1 H),

6.42 (d, J ) 6.2 Hz, 1 H), 5.15 (br s, 1 H), 4.98-4.93 (c, 2 H),

4.69 (m, 1 H), 4.37-4.27 (c, 4 H), 3.39 (s, 3 H), 3.28-3.22 (c,

2 H), 2.32 (s, 3 H), 1.50 (d, J ) 6.6 Hz, 3 H), 1.19 (d, J ) 6.7

Hz, 6 H); MS (APCI) 373 (MH⁺).

(R)-2-(4-Ben zyl-2-m et h yl-p ip er a zin -1-yl)-4-m et h oxy-

m eth yl-6-m eth yl-p yr im id in e (81b). Prepared from guani-

dine bis(trifluoroacetate) salt 80b and 1-methoxy-2,4-pen-

tanedione³³(46d ) (general procedure J ) and purified by flash

column chromatography (1:9 EtOAc/hexanes) to give com-

1

125 mg (89%) of compound 76c as a colorless foam. H NMR

(CDCl₃, 400 MHz) δ 8.56 (s, 1 H), 8.38 (d, J ) 5.0 Hz, 1 H),

8.26 (d, J ) 6.2 Hz, 1 H), 7.29 (d, J ) 5.0 Hz, 1 H), 6.36 (d, J

) 6.2 Hz, 1 H), 5.70 (q, J ) 6.7 Hz, 1 H), 4.73 (m, 1 H), 4.29

(m, 1 H), 4.29 (d, J ) 12.9 Hz, 2 H), 3.45 (d, J ) 12.5 Hz, 2 H),

2.39 (t, J ) 7.5 Hz, 2 H), 1.72-1.64 (c, 2 H), 1.58 (d, J ) 6.8

Hz, 3 H), 1.33 (d, J ) 7.1 Hz, 3 H), 1.31 (d, J ) 6.6 Hz, 3 H),

0.96 (t, J ) 7.5 Hz, 3 H); MS (APCI) 425 (MH⁺).

1R-[4-(3R,5S-Dim eth yl-p ip er a zin -1-yl)p yr im id in -2-yl]-

eth yl Bu tyr a te (78). A mixture of chloropyrimidine 34c (5.0

g, 21.9 mmol) and cis-2,6-dimethyl-piperazine (77, 5.0 g, 43.9

mmol) in THF (150 mL) was heated at reflux for 0.5 h, cooled

to room temperature, and concentrated. The residue was

diluted with saturated aqueous NaHCO₃and extracted with

10% i-PrOH/CHCl₃(3×). The combined organic extracts were

dried (Na₂SO₄), filtered, and evaporated to give 7.2 g (crude,

>100%) of compound 78 as a yellow oil, which was used

without further purification. ¹H NMR (CDCl₃, 400 MHz) δ 8.15

(d, J ) 6.2 Hz, 2 H), 6.31 (d, J ) 6.2 Hz, 1 H), 5.65 (q, J ) 6.8

Hz, 1 H), 4.32-4.15 (c, 2 H), 2.88-2.80 (c, 2 H), 2.44-2.35 (c,

4 H), 1.72-1.59 (c, 2 H), 1.56 (d, J ) 6.6 Hz, 3 H), 1.11 (d, J

) 6.6 Hz, 6 H), 0.94 (t, J ) 7.3 Hz, 3 H); MS (APCI) 307 (MH⁺).

1

pound 81b (70%) as a yellow oil. H NMR (CDCl₃, 300 MHz)

δ 7.42-7.20 (c, 5 H), 6.50 (s, 1 H), 4.92 (m, 1 H), 4.51 (m, 1 H),

4.35 (s, 2 H), 3.61 (d, J ) 13.3 Hz, 1 H), 3.52-3.38 (c, 4 H),

3.20 (td, J ) 12.6, 3.4 Hz, 1 H), 2.88 (d, J ) 10.2 Hz, 1 H),

2.70 (d, J ) 11.2 Hz, 1 H), 2.33 (s, 3 H), 2.21 (dd, J ) 11.0, 3.5

Hz, 1 H), 2.09 (td, J ) 11.7, 3.6 Hz, 1 H), 1.25 (d, J ) 6.6 Hz,

3 H); MS (APCI) 327 (MH⁺).

(R)-4-Meth oxym eth yl-6-m eth yl-2-(2-m eth yl-p ip er a zin -

1-yl)p yr im id in e Hyd r och lor id e (81c). To a solution of

benzyl compound 81b (0.39 g, 1.18 mmol) in MeOH (4 mL)

was added HCl (5.85 M in MeOH, 0.21 mL, 1.25 mmol)

followed by HCO₂NH₄(0.74 g, 11.8 mmol) and 10% Pd/C (39

mg, 10 wt %). This mixture was stirred at reflux for 1 h, cooled

to room temperature, and filtered through Celite. The filtrate

was concentrated and dried under high vacuum to give

compound 81c (100%) as a sticky foam. ¹H NMR (CD₃OD, 400

MHz) δ 6.64 (s, 1 H), 5.19 (m, 1 H), 4.79 (d, J ) 12.2 Hz, 1 H),

4.31 (s, 2 H), 3.42 (s, 3 H), 3.34-3.15 (c, 4 H), 2.99 (td, J )

12.5, 3.9 Hz, 1 H), 2.33 (s, 3 H), 1.28 (d, J ) 7.3 Hz, 3 H); MS

(APCI) 237 (MH⁺).

4-[2-(1R-Bu t yr yloxy-et h yl)-p yr im id in -4-yl]-2R,6S-d i-

m et h yl-p ip er a zin e-1-N,N′-b is(ter t-b u t oxyca r b on yl)ca r -

boxa m id in e (79a ). Prepared from piperazino-pyrimidine 78

(general procedure H) and purified by flash column chroma-

tography (0.5 f 2% MeOH/CHCl₃) to give compound 79a (33%)

Gen er a l P r oced u r e N. Rea ction of Su bstitu ted P ip -

er a zin e 81c w ith Ch lor op yr im id in e 34c. 1R-{4-[4-(4-

Meth oxym eth yl-6-m eth yl-pyr im idin -2-yl)-3R-m eth yl-p ip -

er azin -1-yl]pyr im idin -2-yl}eth yl Bu tyr ate (81d). A mixture

of piperazine hydrochloride salt 81c (0.32 g, 1.17 mmol),

chloropyrimidine 34c (0.27 g, 1.17 mmol), and Et₃N (0.49 mL,

3.52 mmol) in i-PrOH (4 mL) was allowed to stir at reflux for

4 h, cooled to room temperature, concentrated, and purified

by flash column chromatography (1:1 EtOAc/hexanes f EtOAc)

to give 0.46 g (91%) of compound 81d as a colorless oil. ¹H

NMR (CDCl₃, 400 MHz) δ 8.18 (d, J ) 6.2 Hz, 1 H), 6.54 (s, 1

H), 6.35 (d, J ) 6.0 Hz, 1 H), 5.68 (q, J ) 6.8 Hz, 1 H), 4.98

(m, 1 H), 4.56 (m, 1 H), 4.33 (s, 2 H), 4.23-4.11 (c, 2 H), 3.45

(s, 3 H), 3.40-3.28 (c, 2 H), 3.12 (m, 1 H), 2.39 (t, J ) 7.4 Hz,

2 H), 2.34 (s, 3 H), 1.72-1.63 (c, 2 H), 1.57 (d, J ) 6.8 Hz, 3

H), 1.15 (d, J ) 6.5 Hz, 3 H), 0.95 (t, J ) 7.5 Hz, 3 H); MS

(APCI) 429 (MH⁺).

1

as a colorless foam. H NMR (CDCl₃, 400 MHz) δ 9.62 (br s, 1

H), 8.19 (d, J ) 6.2 Hz, 2 H), 6.38 (d, J ) 6.2 Hz, 1 H), 5.66 (q,

J ) 6.8 Hz, 1 H), 4.48-4.12 (c, 4 H), 3.33-3.20 (c, 2 H), 2.38

(t, J ) 7.5 Hz, 2 H), 1.71-1.62 (c, 2 H), 1.56 (d, J ) 6.8 Hz, 3

H), 1.48 (s, 18 H), 1.28 (d, J ) 6.6 Hz, 3 H), 1.26 (d, J ) 6.8

Hz, 3 H), 0.95 (t, J ) 7.5 Hz, 3 H); MS (APCI) 549 (MH⁺).

(R)-4-Ben zyl-2-m et h yl-p ip er a zin e-1-N,N′-b is(ter t-b u -

toxyca r bon yl)ca r boxa m id in e (79b). Prepared from benzyl-

piperazine 72c (general procedure H) and purified by flash

column chromatography (1:9 f 1:4 EtOAc/hexanes) to give

compound 79b (80%) as a light yellow sticky material. ¹H NMR

(CDCl₃, 400 MHz) δ 7.32-7.22 (c, 5 H), 3.78-3.33 (c, 5 H),

2.76 (d, J ) 10.8 Hz, 1 H), 2.61 (d, J ) 11.2 Hz, 1 H), 2.30 (dd,

Sorbitol Dehydrogenase Inhibitors

J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 2 525

(S)-2-(4-Ben zyl-2-m et h yl-p ip er a zin -1-yl)-4-m et h oxy-

3 H), 1.33 (d, J ) 6.9 Hz, 6 H); MS (APCI) 355 (MH⁺). HRMS

(FAB) exact mass calcd for C₁₈H₂₃N₆O₂355.1882 (MH⁺), found

355.1851.

m et h yl-6-m et h yl-p yr im id in e (82a : R¹

) 4-Met h oxy-

m eth yl-6-m eth yl-p yr im id in -2-yl). Prepared from benzyl

piperazine 72b and 2-chloro-4-methoxymethyl-6-methyl-pyr-

imidine³⁴(75c) (general procedure M, refluxing n-BuOH

method) and purified by flash column chromatography (1:9

EtOAc/hexanes) to give compound 82a (31%) as a yellow oil.

¹H NMR (CDCl₃, 400 MHz) δ 7.35-7.21 (c, 5 H), 6.46 (s, 1 H),

4.86 (m, 1 H), 4.46 (d, J ) 13.5 Hz, 1 H), 4.29 (s, 2 H), 3.56 (d,

J ) 13.3 Hz, 1 H), 3.46-3.38 (c, 4 H), 3.17 (td, J ) 12.6, 3.3

Hz, 1 H), 2.85 (d, J ) 10.4 Hz, 1 H), 2.67 (d, J ) 11.2 Hz, 1 H),

2.29 (s, 3 H), 2.17 (dd, J ) 11.0, 3.8 Hz, 1 H), 2.07 (td, J )

11.8, 3.5 Hz, 1 H), 1.23 (d, J ) 6.6 Hz, 3 H); MS (APCI) 327

(MH⁺).

BBr ₃Meth od. 1R-{4-[4-(4-Hydr oxym eth yl-6-m eth yl-pyr -

imidin-2-yl)-2S-methyl-piperazin-1-yl]pyrimidin-2-yl}ethanol

(90: R¹) 4-Hyd r oxym eth yl-6-m eth yl-p yr im id in -2-yl, R²

) r-Me). To a solution of methyl ether butyrate 76e (0.77 g,

1.80 mmol) in CH₂Cl₂(9 mL) at 0 °C with stirring under N₂

was added BBr₃(1.0 M in CH₂Cl₂, 9.0 mL, 9.0 mmol) slowly

dropwise. This mixture was allowed to stir with slow warming

to room temperature for 18 h, quenched by careful addition of

saturated aqueous NaHCO₃, and extracted with 10% i-PrOH/

CHCl₃(3×). The combined organic extracts were dried (Na₂SO₄),

filtered, evaporated, and purified by flash column chromatog-

raphy (1 f 5% MeOH/CHCl₃) to give 0.34 g (55%) of compound

(S)-4-Meth oxym eth yl-6-m eth yl-2-(2-m eth yl-p ip er a zin -

1-yl)p yr im id in e (83a : R¹) 4-Meth oxym eth yl-6-m eth yl-

p yr im id in -2-yl). Prepared from benzyl compound 82a (gen-

eral procedure L) to give compound 83a (100%) as a colorless

1

90 as a yellow sticky material. [R]_D+66.5 (c 1.0, MeOH); H

NMR (CDCl₃, 400 MHz) δ 8.18 (d, J ) 6.0 Hz, 1 H), 6.36 (d, J

) 6.2 Hz, 1 H), 6.32 (s, 1 H), 4.69 (q, J ) 6.6 Hz, 1 H), 4.60-

4.53 (c, 3 H), 4.52 (s, 2 H), 4.38-4.18 (c, 2 H), 3.63 (m, 1 H),

3.40-3.29 (c, 2 H), 3.24 (m, 1 H), 2.32 (s, 3 H), 1.49 (d, J ) 6.6

Hz, 3 H), 1.20 (d, J ) 6.6 Hz, 3 H); MS (APCI) 345 (MH⁺).

Anal. (C₁₇H₂₄N₆O₂‚0.25H₂O) C, H, N.

1

oil. H NMR (CDCl₃, 300 MHz) δ 6.49 (s, 1 H), 4.88 (m, 1 H),

4.49 (m, 1 H), 4.33 (s, 2 H), 3.47 (s, 3 H), 3.12-3.02 (c, 2 H),

2.99 (dd, J ) 11.1, 3.6 Hz, 1 H), 2.88 (d, J ) 11.0 Hz, 1 H),

2.76 (td, J ) 11.0, 3.7 Hz, 1 H), 2.33 (s, 3 H), 1.21 (d, J ) 6.6

Hz, 3 H); MS (APCI) 237 (MH⁺).

K₂CO₃Meth od . 1R-[4-(3S-Meth yl-4-oxa zolo[5,4-c]p yr i-

d in -2-yl-p ip er a zin -1-yl)p yr im id in -2-yl]eth a n ol (95, R¹

)

Oxa zolo[5,4-c]p yr id in -2-yl, R³) â-Me). A mixture of bu-

tyrate 84b (0.20 g, 0.49 mmol) and K₂CO₃(0.20 g, 1.47 mmol)

in MeOH (5 mL) was stirred at room temperature for 4 h,

diluted with saturated aqueous NaHCO₃, and extracted with

10% i-PrOH/CHCl₃(4×). The combined organic extracts were

dried (Na₂SO₄), filtered, evaporated, and purified by flash

column chromatography (1.5 f 5% MeOH/CHCl₃) to give 0.12

g (72%) of compound 95 (65%) as a white foam. [R]_D+61.6 (c

1R-{4-[4-(4-Meth oxym eth yl-6-m eth yl-p yr im id in -2-yl)-

3S-m eth yl-p ip er a zin -1-yl]p yr im id in -2-yl}eth yl Bu tyr a te

(84a : R¹) 4-Meth oxym eth yl-6-m eth yl-p yr im id in -2-yl).

Prepared from piperazine 83a (general procedure N) and

purified by flash column chromatography (1:1 EtOAc/hexanes

f EtOAc) to give compound 84a (87%) as a colorless oil. ¹H

NMR (CDCl₃, 400 MHz) δ 8.17 (d, J ) 6.0 Hz, 1 H), 6.53 (s, 1

H), 6.33 (d, J ) 6.3 Hz, 1 H), 5.66 (q, J ) 6.8 Hz, 1 H), 4.97

(m, 1 H), 4.55 (dt, J ) 13.5, 3.3 Hz, 1 H), 4.32 (s, 2 H), 4.21

(m, 1 H), 3.47-3.44 (c, 4 H), 3.37-3.27 (c, 2 H), 3.09 (m, 1 H),

2.38 (t, J ) 7.4 Hz, 2 H), 2.33 (s, 3 H), 1.72-1.63 (c, 2 H), 1.56

(d, J ) 6.6 Hz, 3 H), 1.12 (d, J ) 6.4 Hz, 3 H), 0.95 (t, J ) 7.5

Hz, 3 H); MS (APCI) 429 (MH⁺).

1

1.0, MeOH); H NMR (CDCl₃, 400 MHz) δ 8.56 (s, 1 H), 8.37

(d, J ) 5.4 Hz, 1 H), 8.25 (d, J ) 6.2 Hz, 1 H), 7.29 (d, J ) 5.2

Hz, 1 H), 6.43 (d, J ) 6.0 Hz, 1 H), 4.72 (m, 1 H), 4.65 (m, 1

H), 4.45 (m, 1 H), 4.29 (m, 1 H), 4.26-4.20 (c, 2 H), 3.58 (td,

J ) 13.2, 3.3 Hz, 1 H), 3.48 (dd, J ) 13.4, 3.9 Hz, 1 H), 3.26

(td, J ) 12.6, 3.7 Hz, 1 H), 1.51 (d, J ) 6.6 Hz, 3 H), 1.34 (d,

J ) 6.7 Hz, 3 H); MS (APCI) 341 (MH⁺). Anal. (C₁₇H₂₀N₆O₂‚

0.75H₂O) C, H; N: calcd, 23.75; found, 23.22.

1R-{4-[4-(4-Hyd r oxym eth yl-6-m eth yl-p yr im id in -2-yl)-

2R,6S-d im et h yl-p ip er a zin -1-yl]p yr im id in -2-yl}et h a n ol

(85: R¹) 4-Hyd r oxym eth yl-6-m eth yl-p yr im id in -2-yl, R²

) R⁶) â-Me). Prepared from methyl ether butyrate 76a

(LiOH method, 3:1:1 MeOH/THF/H₂O, followed by BBr₃method)

and purified by flash column chromatography (1 f 3% MeOH/

CHCl₃) to give compound 85 (69% for two steps) as a white

solid. mp 139-141 °C; [R]_D+14.8 (c 1.0, MeOH); ¹H NMR

(CDCl₃, 300 MHz) δ 8.21 (d, J ) 6.2 Hz, 1 H), 6.37 (d, J ) 6.3

Hz, 1 H), 6.33 (s, 1 H), 4.80 (d, J ) 13.2 Hz, 2 H), 4.72 (q, J )

6.5 Hz, 1 H), 4.68-4.47 (c, 2 H), 4.54 (s, 2 H), 4.39 (br s, 1 H),

3.64 (br s, 1 H), 3.21 (dd, J ) 13.1, 4.5 Hz, 2 H), 2.34 (s, 3 H),

1.52 (d, J ) 6.6 Hz, 3 H), 1.26 (d, J ) 6.6 Hz, 6 H); MS (APCI)

359 (MH⁺). Anal. (C₁₈H₂₆N₆O₂) C, H, N.

1R-[4-(2R,6S-Dim eth yl-4-qu in oxa lin -2-yl-p ip er a zin -1-

yl)p yr im id in -2-yl]eth a n ol (88: R¹) Qu in oxa lin -2-yl, R²

) R⁶) â-Me). Prepared from butyrate 76d (LiOH method,

2:1:1 MeOH/THF/H₂O) and purified by flash column chroma-

tography (1% MeOH/CHCl₃) to give compound 88 (82%) as a

yellow foam. [R]_D+11.1 (c 1.4, MeOH); ¹H NMR (CD₃OD, 300

MHz) δ 8.77 (s, 1 H), 8.17 (d, J ) 6.4 Hz, 1 H), 7.82 (dd, J )

8.3, 1.1 Hz, 1 H), 7.66 (dd, J ) 8.5, 1.4 Hz, 1 H), 7.59 (m, 1 H),

7.40 (m, 1 H), 6.65 (d, J ) 6.4 Hz, 1 H), 4.84-4.62 (c, 5 H),

3.41-3.30 (c, 2 H), 1.47 (d, J ) 6.6 Hz, 3 H), 1.31 (d, J ) 6.8

Hz, 6 H); MS (APCI) 365 (MH⁺). Anal. (C₂₀H₂₄N₆O‚0.5H₂O)

C, H, N.

Gen er a l P r oced u r e O. P r ep a r a tion of Com p ou n d s 85-

97 by Meth yl Eth er a n d /or Bu tyr a te Ester Dep r otection

of P en u ltim a te P r ecu r sor s 76a -h , 81a ,d , a n d 84a -c.

LiOH Meth od . 1R-(4-{4-[2-(1R-Hyd r oxyeth yl)p yr im id in -

4-yl]-2R,6S-d im eth yl-p ip er a zin -1-yl}p yr im id in -2-yl)eth a -

n ol (86: R¹) (R)-2-(1-Hyd r oxyeth yl)p yr im id in -4-yl, R²

) R⁶) â-Me). To a solution of dibutyrate 76b (0.47 g, 0.94

mmol) in a 3:1 mixture of MeOH/H₂O (4 mL) was added LiOH‚

H₂O (0.20 g, 4.71 mmol). This mixture was stirred at room

temperature for 1 h and concentrated. The aqueous residue

was extracted with 10% i-PrOH/CHCl₃(3×), and the combined

organic extracts were dried (Na₂SO₄), filtered, evaporated, and

purified by flash column chromatography (3% MeOH/CHCl₃)

to give 0.26 g (76%) of compound 86 as a white solid. mp 163-

164.5 °C; [R]_D+42.3 (c 1.0, MeOH); ¹H NMR (CDCl₃, 400 MHz)

δ 8.22 (d, J ) 6.0 Hz, 1 H), 8.21 (d, J ) 6.2 Hz, 1 H), 6.45 (d,

J ) 6.2 Hz, 1 H), 6.35 (d, J ) 6.2 Hz, 1 H), 4.74-4.28 (c, 8 H),

3.32-3.27 (c, 2 H), 1.50 (d, J ) 6.6 Hz, 6 H), 1.24 (d, J ) 6.9

Hz, 6 H); MS (APCI) 359 (MH⁺). Anal. (C₁₈H₂₆N₆O₂) C, H, N.

HCl Meth od . 1R-[4-(2R,6S-Dim eth yl-4-oxa zolo[5,4-c]-

p yr id in -2-yl-p ip er a zin -1-yl)p yr im id in -2-yl]eth a n ol (87:

R¹) Oxa zolo[5,4-c]p yr id in -2-yl, R ²) R ⁶) â-Me). To a

solution of butyrate 76c (0.12 g, 0.28 mmol) in MeOH (2.8 mL)

was added concentrated HCl (0.24 mL, 2.8 mmol). This

mixture was stirred for 64 h, quenched to pH 7 by the addition

of 6 N aqueous NaOH followed by 1 N aqueous NaOH, and

concentrated. The aqueous residue was extracted with 10%

i-PrOH/CHCl₃(3×), and the combined organic extracts were

dried (Na₂SO₄), filtered, evaporated, and purified by flash

column chromatography (1 f 3% MeOH/CHCl₃) to give 45 mg

(45%) of compound 87 as a white solid. mp 175-178 (dec); [R]_D

1R-{4-[4-(4-Hyd r oxym eth yl-6-m eth yl-p yr im id in -2-yl)-

3R,5S-d im et h yl-p ip er a zin -1-yl]p yr im id in -2-yl}et h a n ol

(89: R¹) 4-Hyd r oxym eth yl-6-m eth yl-p yr im id in -2-yl, R³

) R⁵) â-Me). Prepared from methyl ether 81a (BBr₃method)

and purified by flash column chromatography (1% MeOH/

CHCl₃) followed by recrystallization (MeOH/EtOAc) to give

compound 89 (46%) as a white solid. mp 149-151 °C; [R]_D

1

+8.1 (c 1.3, MeOH); H NMR (CD₃OD, 300 MHz) δ 8.53 (d, J

) 0.6 Hz, 1 H), 8.28 (d, J ) 5.4 Hz, 1 H), 8.20 (d, J ) 6.2 Hz,

1 H), 7.34 (dd, J ) 5.3, 0.7 Hz, 1 H), 6.68 (d, J ) 6.4 Hz, 1 H),

4.90-4.72 (c, 2 H), 4.69 (q, J ) 6.6 Hz, 1 H), 4.32 (d, J ) 13.3

Hz, 2 H), 3.56 (dd, J ) 13.3, 4.4 Hz, 2 H), 1.47 (d, J ) 6.6 Hz,

1

+18.9 (c 1.1, MeOH); H NMR (CDCl₃, 400 MHz) δ 8.19 (d, J

526 J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 2

Chu-Moyer et al.

1

) 6.2 Hz, 1 H), 6.44 (d, J ) 6.2 Hz, 1 H), 6.32 (s, 1 H), 5.02-

4.97 (c, 2 H), 4.71 (m, 1 H), 4.53 (s, 2 H), 4.48-4.24 (c, 3 H),

3.73 (br s, 1 H), 3.31-3.24 (c, 2 H), 2.33 (s, 3 H), 1.51 (d, J )

6.7 Hz, 3 H), 1.23 (d, J ) 6.9 Hz, 3 H); MS (APCI) 359 (MH⁺).

Anal. (C₁₈H₂₆N₆O₂) C, H, N.

1R-(4-{4-[2-(1R-Hyd r oxyeth yl)p yr im id in -4-yl]-2S-m eth -

yl-p ip er a zin -1-yl}p yr im id in -2-yl)eth a n ol (91: R¹) (R)-

2-(1-Hyd r oxyeth yl)p yr im id in -4-yl, R²) r-Me). Prepared

from dibutyrate 76f (LiOH method, 4:1 MeOH/H₂O) and

purified by flash column chromatography (5 f 10% MeOH/

CHCl₃) to give compound 91 (78%) as a white solid. mp 158-

160 °C; [R]_D+82.5 (c 1.0, MeOH); ¹H NMR (CDCl₃, 400 MHz)

δ 8.24 (d, J ) 6.2 Hz, 2 H), 6.39 (d, J ) 6.0 Hz, 1 H), 6.38 (d,

J ) 6.2 Hz, 1 H), 4.71 (q, J ) 6.6 Hz, 2 H), 4.55 (br s, 1 H),

4.32-4.16 (c, 5 H), 3.60 (dd, J ) 13.5, 3.7 Hz, 1 H), 3.48 (m, 1

H), 3.35 (m, 1 H), 1.52 (d, J ) 6.6 Hz, 6 H), 1.24 (d, J ) 6.4

Hz, 3 H); MS (APCI) 345 (MH⁺). Anal. (C₁₇H₂₄N₆O₂) C, H, N.

(c 1.0, MeOH); H NMR (CDCl₃, 300 MHz) δ 8.19 (d, J ) 6.2

Hz, 1 H), 6.39 (d, J ) 6.2 Hz, 1 H), 6.34 (s, 1 H), 5.03 (m, 1 H),

4.74 (q, J ) 6.8 Hz, 1 H), 4.62 (dt, J ) 12.3, 3.2 Hz, 1 H), 4.56

(s, 2 H), 4.42-4.13 (c, 3 H), 3.68 (br s, 1 H), 3.50-3.37 (c, 2

H), 3.20 (m, 1 H), 2.33 (s, 3 H), 1.53 (d, J ) 6.8 Hz, 3 H), 1.19

(d, J ) 6.7 Hz, 3 H); MS (APCI) 345 (MH⁺). HRMS (FAB) exact

mass calcd for C₁₇H₂₅N₆O₂345.2039 (MH⁺), found 345.2031.

Biology. SDH In h ibition Activity. Recombinant h- or

s-SDH was purchased from Pan Vera Corp. (Madison, WI) or

Boehringer (Germany), respectively. Experimental compounds

were dissolved at 5 mM in 20% (v/v) aqueous DMSO, and 25

µL aliquots were added to 0.2 mL of potassium phosphate

buffer (pH 7.0) containing NAD⁺, iodonitrotetrazolium violet

(INT), and h- or s-SDH. Following a 15 minute incubation at

25 °C, the reaction was initiated by the addition of 20 mM

sorbitol (25 µL). Final concentrations in the assay were 90 mM

potassium phosphate, 1 mM NAD⁺, 1 mM INT, 2 mM sorbitol,

and 2 nM h-SDH or 8 nM s-SDH. Enzyme activity was assayed

with a SLT340 ATTC plate reader (model 16-925, SLT Lab-

Instruments, Austria), which measured the increase in the rate

of INT reduction at 495 nm at 25 °C over 10 min. IC₅₀s were

calculated using a log-linear regression analysis.

Nor m a liza tion of Ner ve F r u ctose in Dia betic Ra ts:

Acu te P r even tion Mod el. Male CD Sprague-Dawley rats

(175-225 g) were made diabetic by injection of STZ (17 mg/

mL in 0.01 M citrate buffer, pH 4.5, 85 mg/kg body wt) into

the tail vein of conscious rats. STZ was administered at

approximately 9:00 a.m. on day 1. The animals were main-

tained with free access to food and water. Test compound was

administered by oral gavage (volume of 5 mL/kg) at 4, 7, and

24 h after STZ administration. Four hours after the final dose

(28 h after STZ administration), animals were sacrificed by

cervical dislocation. The left sciatic nerve was excised, weighed,

and placed in 1 mL of ice-cold 6% perchloric acid and frozen

for fructose analysis at a later date.

Weighed sciatic nerves in 6% (w/v) perchloric acid (1 mL)

were thawed and homogenized with a polytron (Kinematica,

Switzerland). After the mixture was centrifuged, the decanted

supernatant was neutralized by the addition of 3.0 M potas-

sium carbonate (100 µL) and recentrifuged. The fructose

contents of the supernatants were determined enzymatically.³⁵

Briefly, fructose was oxidized to 5-keto-fructose by fructose

dehydrogenase (FDH) with concomitant reduction of resazurin

to the highly fluorescent resorufin. Final assay concentrations

were 0.2 M citric acid, pH 4.5, containing 13.2 µM resazurin,

1.7 units/mL of FDH, and 0.068% (v/v) Triton X-100. Reaction

mixtures were incubated for 60 min at room temperature in a

closed drawer. The sample fluorescence was determined at

excitation ) 560 nm, emission ) 580 nm, and slits of 5 mm

each (Perkin-Elmer model LS50B fluorescence spectropho-

tometer). After the appropriate blanks from each sample were

subtracted, nanomole of fructose in each sample was then

determined by comparison with a linear regression of the

fructose standards.

Nor m a liza tion of Ner ve F r u ctose in Dia betic Ra ts:

Ch r on ic Rever sa l Mod el. Male CD Sprague-Dawley rats

(175-225 g) were made diabetic by the injection of STZ (17

mg/mL in 0.01 M citrate buffer, pH 4.5, 85 mg/kg body wt)

into the tail vein of conscious rats. STZ was administered at

approximately 9:00 a.m. on day 1. The animals were main-

tained with free access to food and water. On day 8, at 9:00

a.m., test compound was administered by oral gavage (volume

of 5 mL/kg). Dosing continued once daily at 9:00 a.m. for 5

days. Four hours after the final dose (day 12), animals were

sacrificed by cervical dislocation. The left sciatic nerve was

excised, weighed, and placed in ice-cold 6% (w/v) perchloric

acid (1 mL) and frozen for fructose analysis at a later date,

using the methods described above.

1R-{4-[4-(4-Hyd r oxym eth yl-6-m eth yl-p yr im id in -2-yl)-

2R-m eth yl-p ip er a zin -1-yl]p yr im id in -2-yl}eth a n ol (92: R¹

) 4-Hyd r oxym eth yl-6-m eth yl-p yr im id in -2-yl, R ²) â-Me).

Prepared from methyl ether butyrate 76g (LiOH method, 3:1

MeOH/H₂O, followed by BBr₃method) and purified by flash

column chromatography (1 f 2% MeOH/CHCl₃) to give

compound 92 (84% for two steps) as a white foam. [R]_D-35.0

1

(c 1.1, MeOH); H NMR (CDCl₃, 400 MHz) δ 8.21 (d, J ) 6.2

Hz, 1 H), 6.37 (d, J ) 6.2 Hz, 1 H), 6.33 (s, 1 H), 4.72 (m, 1 H),

4.67-4.54 (c, 3 H), 4.54 (s, 2 H), 4.34 (m, 1 H), 4.20 (m, 1 H),

3.58 (br s, 1 H), 3.42-3.32 (c, 2 H), 3.26 (m, 1 H), 2.34 (s, 3 H),

1.51 (d, J ) 6.5 Hz, 3 H), 1.21 (d, J ) 6.6 Hz, 3 H); MS (APCI)

345 (MH⁺). Anal. (C₁₇H₂₄N₆O₂‚0.25H₂O) C, H, N.

1R-(4-{4-[2-(1R-Hydr oxyeth yl)pyr im idin -4-yl]-2R-m eth -

yl-p ip er a zin -1-yl}p yr im id in -2-yl)eth a n ol (93: R¹) (R)-

2-(1-Hyd r oxyeth yl)p yr im id in -4-yl, R²) â-Me). Prepared

from dibutyrate 76h (LiOH method, 4:1 MeOH/H₂O) and

purified by flash column chromatography (5 f 10% MeOH/

CHCl₃) to give compound 93 (77%) as a white solid. mp 155-

157 °C; [R]_D-30.4 (c 0.9, MeOH); ¹H NMR (CDCl₃, 400 MHz)

δ 8.24 (d, J ) 6.0 Hz, 2 H), 6.39 (d, J ) 6.0 Hz, 1 H), 6.38 (d,

J ) 6.0 Hz, 1 H), 4.74-4.71 (c, 2 H), 4.58 (br s, 1 H), 4.32-

4.16 (c, 5 H), 3.59 (m, 1 H), 3.50 (m, 1 H), 3.38 (m, 1 H), 1.52

(d, J ) 6.6 Hz, 6 H), 1.25 (d, J ) 6.5 Hz, 3 H); MS (APCI) 345

(MH⁺). Anal. (C₁₇H₂₄N₆O₂‚0.33H₂O) C, H, N.

1R-{4-[4-(4-Hyd r oxym eth yl-6-m eth yl-p yr im id in -2-yl)-

3S-m eth yl-p ip er a zin -1-yl]p yr im id in -2-yl}eth a n ol (94: R¹

) 4-Hyd r oxym eth yl-6-m eth yl-p yr im id in -2-yl, R ³) â-Me).

Prepared from methyl ether butyrate 84a (BBr₃method) and

purified by flash column chromatography (2% MeOH/CHCl₃)

to give compound 94 (31%) as a yellow oil. [R]_D+68.1 (c 0.7,

1

MeOH); H NMR (CDCl₃, 400 MHz) δ 8.17 (d, J ) 6.2 Hz, 1

H), 6.36 (d, J ) 6.2 Hz, 1 H), 6.33 (s, 1 H), 4.99 (m, 1 H), 4.97

(m, 1 H), 4.69 (m, 1 H), 4.58 (m, 1 H), 4.52 (s, 2 H), 4.40-4.11

(c, 3 H), 3.60 (br s, 1 H), 3.45-3.34 (c, 2 H), 3.19 (m, 1 H), 2.32

(s, 3 H), 1.49 (d, J ) 6.6 Hz, 3 H), 1.16 (d, J ) 6.7 Hz, 3 H);

MS (APCI) 345 (MH⁺). HRMS (FAB) exact mass calcd for

C

₁₇H₂₅N₆O₂345.2039 (MH⁺), found 345.2037.

1R-[4-(3S-Meth yl-4-qu in oxa lin -2-yl-p ip er a zin -1-yl)p yr -

im id in -2-yl]et h a n ol (96: R¹) Qu in oxa lin -2-yl, R³

)

â-Me). Prepared from butyrate 84c (LiOH method, 4:1 MeOH/

H₂O) and purified by flash column chromatography (2%

MeOH/CHCl₃) to give compound 96 (78%) as a yellow foam.

1

[R]_D+57.0 (c 1.2, CHCl₃); H NMR (CDCl₃, 400 MHz) δ 8.56

(s, 1 H), 8.23 (d, J ) 6.2 Hz, 1 H), 7.89 (d, J ) 8.3 Hz, 1 H),

7.69 (d, J ) 8.5 Hz, 1 H), 7.59 (t, J ) 7.5 Hz, 1 H), 7.41 (t, J

) 7.6 Hz, 1 H), 6.42 (d, J ) 6.2 Hz, 1 H), 4.78 (m, 1 H), 4.73

(m, 1 H), 4.43 (m, 1 H), 4.38-4.23 (c, 2 H), 3.64-3.52 (c, 2 H),

3.38 (m, 1 H), 1.52 (d, J ) 6.6 Hz, 3 H), 1.30 (d, J ) 6.6 Hz, 3

H); MS (APCI) 351 (MH⁺). HRMS (FAB) exact mass calcd for

C

₁₉H₂₃N₆O 351.1902 (MH⁺), found 351.1933.

1R-{4-[4-(4-Hyd r oxym eth yl-6-m eth yl-p yr im id in -2-yl)-

P h a r m a cok in etic Eva lu a tion . Ra t Stu d ies. Male CD

Sprague-Dawley rats³⁶were fasted overnight and then dosed

by oral gavage at 5 mg/kg/day (compounds 62, 67, 69, and 86)

or 20 mg/kg/day (compound I). The compounds were formu-

lated in pH-adjusted deionized water (pH ∼4-5). Water was

provided ad libitum. Blood samples (800 µL) were collected

3R-m eth yl-p ip er a zin -1-yl]p yr im id in -2-yl}eth a n ol (97: R¹

) 4-Hyd r oxym eth yl-6-m eth yl-p yr im id in -2-yl, R³) r-Me).

Prepared from methyl ether butyrate 81d (BBr₃method) and

purified by flash column chromatography (1 f 5% MeOH/

CHCl₃) to give compound 97 (48%) as a colorless oil. [R]_D-40.6

Sorbitol Dehydrogenase Inhibitors

J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 2 527

242. (c) Geisen, K.; Utz, R.; Gro¨tsch, H.; Lang, H. J .; Nimmes-

gern, H. Sorbitol-accumulating Pyrimidine Derivatives. Arzneim.-

Forsch./ Drug Res. 1994, 44 (II), 1032-1043.

via venous orbital bleed at designated time points, and serum

was stored at -20 °C until assay.

An a lytica l Meth od s. Serum samples (300 µL) were ana-

lyzed at selected time points and combined with an internal

standard. This mixture was diluted with distilled H₂O (1 mL),

extracted with EtOAc (5 mL), evaporated to dryness, and

reconstituted in the mobile phase (150 µL). These extracts (120

µL) were analyzed by reverse phase HPLC using a Kromasil

C4 column (250 × 4.6 mm) and elution with a 1:1 MeOH/H₂O

mobile phase containing 10 mL Pic-B7³⁷/liter solution. The flow

rate was set at 1.0 mL/min, and UV detection at 237 nM was

used. The standard curves for tested analogues were linear

from 50 to 5000 ng/mL.

P h a m a cok in et ic/P h a r m a cod yn a m ic E va lu a t ion of

Com p ou n d 86. Male CD Sprague-Dawley rats (150-175 g)

were made diabetic by injection of STZ (17 mg/mL in 0.01 M

citrate buffer, pH 4.5, 85 mg/kg body wt). The animals were

maintained with free access to food and water. On the fifth

day following STZ administration, rats were dosed with

compound 86 via oral gavage at 6 a.m. At selected time points

thereafter, animals (n ) 5/group) were sacrificed by decapita-

tion. Blood was collected for assay of serum drug levels (see

above, pharmacokinetic evaluation analytical methods). A

sciatic nerve was excised, stripped of adhering fat, blotted, and

weighed before being placed in 6% (w/v) perchloric acid (1.0

mL) for subsequent fructose assay.³⁵

(9) (a) Obrosova, I. G.; Fathallah, L.; Lang, H. J .; Greene, D. A.

Evaluation of a Sorbitol Dehydrogenase Inhibitor on Diabetic

Peripheral Nerve Metabolism. A Prevention Study. Diabetologia

1999, 42, 1187-1194. (b) Ng, D. T. F.; Lee, F. K.; Song, Z. T.;

Calcutt, N. A.; Lee, L. W.; Chung, S. S. M.; Chung, S. K. Effects

of Sorbitol Dehydrogenase Deficiency on Nerve Conduction in

Experimental Diabetic Mice. Diabetes 1998, 47, 961-966. (c)

Cameron, N. E.; Cotter, M. A.; Basso, M.; Hohman, T. C.

Comparison of the Effects of Inhibitors of Aldose Reductase and

Sorbitol Dehydrogenase on Neurovascular Function, Nerve

Conduction and Tissue Polyol Pathway Metabolites in Strepto-

zotocin-diabetic Rats. Diabetologia 1997, 40, 271-281.

(10) Mylari, B. L.; Oates, P. J .; Beebe, D. A.; Brackett, N. S.; Coutcher,

J . B.; Dina, M. S.; Zembrowski, W. J . Sorbitol Dehydrogenase

Inhibitors (SDIs): A New Potent, Enantiomeric SDI, 4-[2-(1R-

Hydroxyethyl)-pyrimidin-4-yl]-piperazine-1-sulfonic acid di-

methylamide. J . Med. Chem. 2001, 44, 2695-2700.

(11) Ballinger, W. E.; Day, W. W.; Beebe, D. A.; Oates, P. J .;

Zembrowski, W. J .; Mylari, B. L. The Effect of Multiple Bolus

Dosing vs Chronic Water Dosing with CP-166,572, a Potent

Sorbitol Dehydrogenase Inhibitor, on Nerve Fructose Normaliza-

tion in Diabetic Rats. 7th North American ISSX Meeting, San

Diego, CA, October 1996.

(12) Geisen, K.; Utz, R.; Hildegard, N.; Lang, H.-J . Substituted

Pyrimidine Derivatives, A Process for the Preparation Thereof

and the Use Thereof as Reagents. U.S. Patent 5,215,990.

(13) Chu-Moyer, M. Y.; Murry, J . A.; Mylari, B. L.; Zembrowski, W.

J . Sorbitol Dehydrogenase Inhibiting Pyrimidines. WO Patent

0059510.

(14) These compounds are commercially available or known in the

literature. See Experimental Section for details.

Su p p or tin g In for m a tion Ava ila ble: Complete experi-

mental procedures for the preparation of compounds 3b-k ;

7a -d ,f,h ; 35b-d ; 36a -i,k -o; 39b-d ; 47b-d ; 74b,c; 76a ,d -

h ; 82b,c; 83b,c; 84b,c. This material is available free of charge

via the Internet at http://pubs.acs.org.

(15) In certain cases, oxidation of the sulfur-containing heterocycle

in R¹(3g: R¹) benzo[d]isothiazol-3-yl f 3k : R¹) benzo[d]-

isothiazol-3-yl S,S-dioxide) or hydrogenation of heteroaromatic

chlorines in R¹(7a : R¹) 2-chloropyrimidin-4-yl f 7g: R¹

)

pyrimidin-4-yl, 7b: R¹) 4,6-dichlorotriazin-2-yl f 7h : R¹

triazin-2-yl) was necessary to ultimately provide the desired

target compounds. See Experimental Section for details.

(16) In one case, deprotection of a methyl ether protecting group was

necessary prior to hydrolysis of the ester protecting group to

provide the desired compound (36h : R¹) 4-methoxymethyl-6-

methylpyrimidin-2-yl f 36i: R¹) 4-hydroymethyl-6-methyl-

pyrimidin-2-yl). See Experimental Section for details.

(17) Kim, K. S.; Qian, L. Improved Method for the Preparation of

Guanidines. Tetrahedron Lett. 1993, 34, 7677-7680.

(18) Kucerovy, A.; Mattner, P. G.; Hathaway, J . S.; Repic, O.

Improved Synthesis of Fluoroalkyl and Fluoroaryl Substituted

2-Aminopyrimidines. Synth. Commun. 1990, 23, 913-917.

(19) Saavedra, J . E.; Lyle, G. G.; Lyle, R. E. Selective N-substitution

of 2,6-Dimethylpiperazine. Org. Prep. Proceed. Int. 1976, 8, 19-

23.

Ack n ow led gm en t. We thank F. Michael Mangano

and Michael S. Dina for the preparation of 22 and 52,

respectively.

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J M010440G

Article Doi

Orally-effective, long-acting sorbitol dehydrogenase inhibitors: Synthesis, structure - Activity relationships, and in vivo evaluations of novel heterocycle-substituted piperazino-pyrimidines

DOI: 10.1021/jm010440g

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