Selective reduction of peptidic ergot alkaloids

Article abstract of DOI:10.1135/cccc20001762

Five 6′-deoxoergopeptines were prepared in 51-68% yield by selective reduction of parent alkaloids with lithium aluminium hydride in tetrahydrofuran at low temperature. New compounds were characterized by mass spectrometry and NMR spectroscopy. The conformation of the peptide part in starting compounds and reduced derivatives is discussed on the basis of crystal structure determination of 6′-deoxo-9,10-dihydroergotamine dihydrate butan 2-one solvate as a representative member of the series.

Full text of DOI:10.1135/cccc20001762

1762
Cvak et al.:
SELECTIVE REDUCTION OF PEPTIDIC ERGOT ALKALOIDS+
Ladislav CVAKa1, Josef STUCHLÍKa2, Magdalena SCHREIBEROVÁ ,
a
c1
Petr SEDMERAb1,*, Vladimír HAVLÍČEKb2, Miroslav FLIEGERb3, Jan ČEJKA ,
c2
d
Bohumil KRATOCHVÍL and Alexandr JEGOROV
a
1
Galena Co., R&D, 747 70 Opava-Komárov, Czech Republic; e-mail: ladislav_cvak@galena.cz,
josef_stuchlik@galena.cz
Institute of Microbiology, Academy of Sciences of the Czech Republic, Vídeňská 1083,
142 20 Prague 4, Czech Republic; e-mail: sedmera@biomed.cas.cz, vlhavlic@biomed.cas.cz,
2
b
1
2
3
flieger@biomed.cas.cz
c
Department of Solid State Chemistry, Institute of Chemical Technology, Prague, Technická 5,
1
2
166 28 Prague 6, Czech Republic; e-mail: cejkaj@vscht.cz, kratochb@vscht.cz
Galena Co., Research Unit, Branišovská 31, 370 05 České Budějovice, Czech Republic;
e-mail: alexandr_jegorov@galena.cz
d
Received May 19, 2000
Accepted October 24, 2000
Five 6′-deoxoergopeptin es were prepared in 51–68% yield by selective reduction of paren t al-
kaloids with lith ium alum in ium h ydride in tetrah ydrofuran at low tem perature. New com -
poun ds were ch aracterized by m ass spectrom etry an d NMR spectroscopy. Th e con form ation
of th e peptide part in startin g com poun ds an d reduced derivatives is discussed on th e basis
of crystal structure determ in ation of 6′-deoxo-9,10-dih ydroergotam in e dih ydrate butan -
2-on e solvate as a represen tative m em ber of th e series.
Key w ord s: In dole alkaloids; Ergot alkaloids; Ergopeptin es; Peptides; Reduction s; NMR spec-
troscopy; Mass spectrom etry; Crystal structure determ in ation ; X-Ray diffraction .
Despite th e rath er lon g h istory of ergot alkaloids in volvin g m an y syn th etic
an d sem isyn th etic attem pts2–4, relatively little atten tion was paid to th e
m odification of peptidic alkaloids in th e cyclol part. So far described exam -
ples in clude so-called aci-isom erization 5–7 at C-2′, m etabolic m odification s
of th e prolin e residue8–10, alkylation of th e acetal h ydroxyl group11–13, pyro-
lysis14, an d Birch reduction 15. Reduction of all th ree carbon yl groups of
ergopeptin es with LiAlH4 in 4-eth ylm orph olin e at 70 °C was also de-
+ In th is 22n d paper on structure an d polym orph ism of ergot derivatives we report syn th esis
an d crystal structure determ in ation of ergopeptin e alkaloids with an un usual m odification
in th e cyclol part. For th e precedin g paper of th e series see ref.1
Collect. Czech. Chem. Commun. (Vol. 65) (2000)

Peptidic Ergot Alkaloids
1763
scribed16. Our strategy for obtain in g m odified ergopeptin e alkaloids was
based on lith ium alum in ium h ydride reduction at low tem peratures17. Th is
paper provides a full accoun t of th is work.
EXPERIMENTAL
Meltin g poin ts were determ in ed on a Kofler apparatus an d were n ot corrected. Optical rota-
tion s were m easured in 1% ch loroform solution s.
All m ass spectra were recorded in th e positive-ion m ode on a double focusin g in strum en t
Fin n igan MAT 90 of BE geom etry. Con dition s for electron im pact were: ion isin g en ergy
70 eV, source tem perature 250 °C, em ission curren t 1 m A, acceleration voltage 5 kV, direct
in let 190–220 °C. High -resolution m easurem en ts were carried out by HR m agn etic scan n in g
with perfluorokerosen e as an in tern al stan dard. Th e m olecular weigh ts were obtain ed by FAB
MS. Th e stan dard saddle field FAB gas-gun was operated at 1 m A curren t an d 6 keV en ergy
with xen on 4.0 (1 · 10–2 Pa) an d m on oth ioglycerol m atrix (Sigm a, St. Louis, U.S.A.); m ag-
n etic calibration was perform ed with CsI as a stan dard.
1H an d 13C NMR spectra (399.95 an d 100.58 MHz, respectively) were m easured on a
Varian VXR-400 spectrom eter in CDCl3 at 25 °C usin g tetram eth ylsilan e as an in tern al stan -
dard. Ch em ical sh ifts are given in ppm (δ-scale), couplin g con stan ts (J) in Hz. Multiplicity
of carbon sign als was determ in ed by APT an d DEPT; th e reported assign m en t is based on
J-resolved, COSY, LR COSY, an d HETCOR experim en ts. A com parison of assign m en t of NMR
sign als for th e paren t alkaloids 1–5, th eir 6′-deoxo-derivatives, 6, 7, 9, 10, 11, an d 6′-deoxo-
ergocristin in e (8) are sum m arized in Tables I–III.
Crystal Structure Determ in ation of 6′-Deoxo-9,10-dih ydroergotam in e Dih ydrate
Butan -2-on e Solvate (11b)
6′-Deoxo-9,10-dih ydroergotam in e (11; 70 m g) was dissolved in butan -2-on e (2 m l) un der
sh ort reflux an d th e solution was allowed to cool in an open flask overn igh t. Th e form ed
crystals were separated an d dried in air. 11b : (C33H39N5O4)·2H2O·C4H8O, Mr = 677.84,
orth orh om bic system , space group C2 (No. 5), a = 25.615(6) Å, b = 10.011(4) Å, c =
17.974(4) Å, β = 126.66(3)°, V = 3 697(2) Å3, Z = 4, Dcalc = 1.22 g cm –3, µ(CuKα) = 0.687
m m –1, F(000) = 1 456.
Th e structure of 11b was solved by direct m eth ods. All n on -H atom s, except of
butan -2-on e, were refin ed an isotropically by full-m atrix least-squares based on F-values. Th e
h ydrogen atom s were set accordin g to th e expected geom etry, th e O an d N h ydrogen s were
localized from th e ∆ρ m ap. Data collection an d refin em en t param eters are listed in Table IV.
Con secutive n um berin g of in dividual C, N, O atom s were used as in dicated in Fig. 1. Water
m olecules were den oted as H801–O80–H802, H901–O90–H902, an d n um bers C71–C74 an d
O75 were used for butan -2-on e. Th e packin g of m olecules in th e structure is sh own in Figs
2a an d 2b.
Reduction of Ergopeptin es. Gen eral Procedure
Solution of an ergopeptin e (18 m m ol dissolved in 250 m l of dry tetrah ydrofuran ) was
dropped in to a LiAlH4 suspen sion (12.0 g, 316 m m ol; in 200 m l of THF) at –5 °C. Th e reac-
tion was perform ed with α-ergokryptin e (1), ergocristin e (2), 9,10-dih ydro-α-ergokryptin e
Collect. Czech. Chem. Commun. (Vol. 65) (2000)

1764
Cvak et al.:
TABLE I
13C NMR ch em ical sh ifts (100.58 MHz, CDCl3) of n ew 6′-deoxoergopeptin es 6–11 an d th eir paren t com -
poun ds 1–5
Com poun d
Carbon
1a
2
3
4
5
6
7
8
9
10
11
2
3
119.07 119.14 117.91 117.91 117.87 119.28 119.11 118.42 117.91 117.88 117.93
110.77 110.43 111.12 111.61 111.52 109.59 110.58 109.79 111.08 111.38 111.14
4
21.55
59.17
48.04
44.29
21.73
59.30
48.26
44.31
26.71
66.55
58.86
43.44
30.08
39.75
26.98
66.71
59.20
44.16
30.51
40.08
26.87
66.65
58.94
42.96
21.95
59.51
48.81
43.54
21.78
59.35
48.53
44.40
27.50
62.77
54.61
43.88
26.83
66.25
58.51
43.37
30.14
39.87
26.91
66.48
58.87
43.81
30.43
40.03
26.77
66.44
58.73
43.13
30.25
39.88
5
7
8
9
118.94 118.52
139.08 139.14
30.57 119.28 118.69 117.76
39.98 137.10 139.04 137.08
10
11
12
13
14
15
16
17
18
129.70 129.42 131.84 132.13 132.11 128.68 129.51 127.27 131.82 132.01 131.93
112.00 111.73 113.05 113.28 113.25 118.86 111.95 112.74 112.88 113.17 113.18
123.36 123.13 123.10 123.26 123.18 123.03 123.25 123.22 122.96 123.10 123.04
110.03 110.08 108.82 108.85 108.82 110.17 110.03 110.11 108.66 108.73 108.75
133.82 133.81 133.32 133.41 133.38 133.66 133.84 133.84 133.27 133.30 133.29
126.23 126.19 125.92 126.06 126.03 125.97 126.20 126.11 125.89 125.97 125.94
40.89
176.22 176.04 175.89 175.43 175.06 175.97 176.25 176.42 175.52 175.67 175.54
89.68 89.88 90.00 89.87 85.79 88.58 88.68 88.79 88.49 88.64 88.83
165.76 165.63 165.97 165.04 165.63 166.16 165.82 165.34 165.78 165.23 166.26
40.88
42.82
43.04
43.57
40.86
40.99
43.24
42.95
43.00
42.83
2′
3′
5′
53.28
56.65
53.41
57.10
57.32
49.25
55.44
54.17
20.55
23.13
70.01
52.12
52.36
54.09
20.81
23.19
69.86
51.89
52.23
54.05
20.81
23.15
69.82
49.55
55.45
54.18
20.64
23.15
70.00
52.26
52.59
54.07
20.83
23.16
69.76
52.29
52.48
54.04
20.78
23.19
71.16
6′
166.14 165.32 165.34 165.03 164.91
8′
45.95
22.08
26.46
64.46
46.09
22.20
26.40
64.30
46.01
22.05
26.35
64.37
46.21
22.28
26.47
64.23
46.25
22.23
26.48
65.39
9′
10′
11′
12′
103.47 103.65 103.73 103.87 103.42 105.61 105.68 105.38 105.73 105.73 105.38
a
Ref.24 Addition al sign als: 1 – R1: 34.26 d, 16.89 q, 15.35 q, R2: 43.77 t, 25.05 d, 22.58 q, 22.19 q; 2 – R1:
34.27 d, 16.74 q, 15.27 q, R2: 39.55 t, 138.85 s, 129.94 d (2 C), 127.86 d (2 C), 126.14 d; 3 – R1: 34.04 d,
16.96 q, 15.57 q, R2: 43.47 t, 25.00 d, 22.64 q, 22.00 q; 4 – R1: 34.26 d, 16.98 q, 15.52 q, R2: 39.46 t, 138.52 s,
130.08 d (2 C), 127.97 d (2 C), 126.33 d; 5 – R1: 24.83 q, R2: 39.35 t, 138.16 s, 130.16 d (2 C), 127.94 d (2 C),
126.36 d; 6 – R1: 34.39 d, 17.13 q, 15.44 q, R2: 41.60 t, 24.77 d, 22.72 q, 22.46 q; 7 – R1: 34.47 d, 17.10 q,
15.37 q, R2: 37.95 t, 139.04 s, 129.67 d (2 C), 128.37 d (2 C), 126.23 d; 8 – R1: 34.20 d, 17.19 q, 15.54 q,
R2: 37.79 t, 139.04 s, 129.67 d (2 C), 128.32 d (2 C), 126.15 d; 9 – R1: 35.54 d, 17.29 q, 15.71 q, R2: 41.61 t,
24.89 d, 22.74 q, 22.51 q; 10 – R1: 34.39 d, 17.25 q, 15.61 q, R2: 37.98 t, 138.83 s, 129.72 d (2 C), 126.38 d (2 C),
126.28 d; 11 – R1: 25.27 q, R2: 37.99 t, 138.73 s, 129.64 d (2 C), 126.28 d (2 C), 126.28 d.
Collect. Czech. Chem. Commun. (Vol. 65) (2000)

Peptidic Ergot Alkaloids
1765
TABLE II
1H NMR ch em ical sh ifts (399.95 MHz, CDCl3) of n ew 6′-deoxoergopeptin es 6–11 an d th eir paren t com -
poun ds 1–5
Com poun d
Proton
1a
2
3
4
5
6
7
8
9
10
11
2
4a
4e
5
7a
7e
8
9a
9e
10
12
13
14
N1-H
17
CONH
5′
6′d
6′u
8′d
8′u
9′d
9′u
10′d
10′u
11′
12′-OH
6.937
2.851
3.332
3.878
2.963
2.921
3.171
6.374
–
6.801
2.715
3.212
3.742
2.713
2.789
3.041
6.275
–
6.864
2.652
3.379
2.153
2.340
3.121
2.728
1.516
2.797
2.910
6.806
7.135
7.185
8.231
2.453
6.670
4.531
–
6.984
2.671
3.422
2.239
2.418
3.141
2.757
1.697
2.778
2.964
6.937
7.198
7.198
7.977
2.502
6.328
4.708
–
6.894
2.769
3.509
2.313
2.488
3.217
2.829
1.743
2.846
3.034
7.013
7.285
7.308
8.282
2.586
6.719
4.832
–
6.922
2.836
3.303
3.806
2.882
2.978
3.246
6.281
–
6.838
2.705
3.208
3.738
2.838
2.748
3.055
6.280
–
6.801
2.571
3.499
3.132
2.641
3.062
2.994
6.480
–
6.830
2.615
3.353
1.931
2.169
3.075
2.671
1.137
2.573
2.809
6.619
7.073
7.183
8.657
2.436
6.362
4.278
3.093
2.229
3.222
2.167
1.971
1.770
2.090
1.980
2.122
6.972
6.864
2.626
3.372
2.090
2.312
3.101
2.714
1.478
2.693
2.887
6.789
7.114
7.183
8.269
2.449
6.405
4.333
3.040
1.999
3.205
2.171
2.007
1.770
2.122
1.871
2.148
7.133
6.834
2.598
3.330
2.066
2.290
3.070
2.746
1.502
2.681
2.857
6.792
7.103
7.166
8.457
2.385
9.467
4.332
3.053
2.007
3.202
2.147
1.998
1.765
2.131
1.964
1.998
6.765
–
–
–
–
–
7.129
7.182
7.235 7.117
8.138
2.709
9.783
4.518
–
7.005
7.067
7.076
7.158
7.220
8.294
2.654
9.484
4.233
3.064
2.154
3.190
2.119
1.948
1.753
2.084
1.968
2.055
7.292
7.007
7.075
7.138
8.323
2.545
9.485
4.227
2.954
1.891
3.128
2.039
1.890
1.672
2.106
1.905
2.022
7.486
6.997
7.034
7.113
9.268
2.518
9.928
4.155
2.915
1.841
3.114
2.010
1.895
1.678
2.010
2.010
2.033
7.726
8.318
2.525
9.636
4.597
–
–
–
–
–
–
3.608
3.545
2.071
1.803
2.189
2.149
3.659
7.372
3.552
3.447
1.967
1.701
2.115
2.006
3.586
7.504
3.620
3.548
2.144
1.802
2.160
2.035
3.686
7.161
3.650
3.562
2.074
1.812
2.128
2.112
3.698
7.152
3.758
3.669
2.161
1.901
2.238
2.238
3.651
6.719
a
Ref.24 Addition al sign als: 1 – R1: 2.095 (1 H, qq), 1.025 (3 H, d, J = 6.7), 0.909 (3 H, d, J = 6.7), R2: 1.993
(1 H, ddd, J = 13.7, 9.7, 6.0), 1.874 (1 H, ddd, J = 13.7, 7.6, 6.2), 2.078 (1 H, m ), 1.048 (3 H, d, J = 6.4),
1.006 (3 H, d, J = 6.4); 2 – R1: 1.975 (1 H, qq), 0.918 (3 H, d, J = 6.9), 0.798 (3 H, d, J = 6.4), R2: 3.351 (1 H,
m ), 3.201 (1 H, m ), 7.385 (2 H, m ), 7.184 (2 H, m ), 7.099 (1 H, m ); 3 – R1: 2.195 (1 H, qq), 0.985 (3 H, d,
J = 6.7), 1.141 (3 H, d, J = 6.9), R2: 1.968 (1 H, ddd, J = 13.4, 8.3, 5.4), 1.870 (1 H, ddd, J = 13.4, 8.1, 5.7),
2.050 (1 H, m ), 0.975 (3 H, d, J = 6.5), 1.049 (3 H, d, J = 6.4); 4 – R1: 2.130 (1 H, qq), 1.108 (3 H, d, J = 6.9),
0.948 (3 H, d, J = 6.8), R2: 3.472 (1 H, m ), 3.256 (1 H, m ), 7.428 (2 H, m ), 7.428 (2 H, m ), 7.269 (1 H, m ); 5 –
R1: 1.667 (3 H, s), R2: 3.604 (1 H, m ), 3.361 (1 H, m ), 7.533 (2 H, m ), 7.372 (2 H, m ), 7.298 (1 H, m ); 6 –
R1: 2.108 (1 H, qq), 0.918 (3 H, d, J = 6.7), 1.030 (3 H, d, J = 6.8), R2: 2.048 (1 H, ddd, J = 13.7, 8.4, 6.0),
1.584 (1 H, ddd, J = 13.7, 7.9, 6.6), 1.726 (1 H, m ), 1.025 (3 H, d, J = 6.5), 0.976 (3 H, d, J = 6.6); 7 – R1:
2.031 (1 H, qq), 0.828 (3 H, d, J = 6.7), 0.944 (3 H, d, J = 6.8), R2: 3.374 (1 H, dd, J = 13.3, 11.5), 2.977 (1 H,
dd, J = 13.3, 3.5), 7.243 (2 H, m ), 7.206 (2 H, m ), 7.122 (1 H, m ); 8 – R1: 2.010 (1 H, qq), 0.824 (3 H, d, J =
6.7), 1.069 (3 H, d, J = 6.8), R2: 3.340 (1 H, dd, J = 13.4, 11.7), 2.956 (1 H, dd, J = 13.4, 3.6), 7.205 (2 H,
m ), 7.217 (2 H, m ), 7.094 (1 H, m ); 9 – R1: 2.198 (1 H, qq), 1.168 (3 H, d, J = 6.8), 1.052 (3 H, d, J = 6.8),
R2: 2.065 (1 H, ddd, J = 13.6, 8.3, 5.9), 1.635 (1 H, ddd, J = 13.6, 7.9, 6.7), 1.788 (1 H, m ), 0.996 (3 H, d, J =
6.6), 1.045 (3 H, d, J = 6.5); 10 – R1: 2.194 (1 H, qq), 1.131 (3 H, d, J = 6.8), 0.990 (3 H, d, J = 6.7), R2:
3.043 (1 H, dd, J = 13.4, 11.0), 3.096 (1 H, dd, J = 13.4, 4.3), 7.333 (2 H, m ), 7.286 (2 H, m ), 7.199 (1 H,
m ); 11 – R1: 1.633 (3 H, s), R2: 3.423 (1 H, dd, J = 13.4, 11.0), 3.101 (1 H, dd, J = 13.4, 4.4), 7.331 (2 H, m ),
7.293 (2 H, m ), 7.208 (1 H, m ).
Collect. Czech. Chem. Commun. (Vol. 65) (2000)

1766
Cvak et al.:
TABLE III
Selected proton -proton couplin g con stan ts of n ew 6′-deoxoergopeptin es 6–11 an d th eir paren t com -
poun ds 1–5
Com poun d
Proton s
1a
2
3
4
5
6
7
8
9
10
11
2,NH
2,4a
1.8
2.0
1.8
1.7
1.8
1.8
1.8
1.8
1.9
1.8
2.0
1.8
–14.1
12.0
4.9
1.0
2.0
–
1.6
–14.1
12.0
4.3
1.0
1.9
–
1.8
–14.8
11.2
4.4
–
1.8
–14.7
11.2
4.4
1.7
–14.7
11.0
4.3
1.8
–14.1
11.8
4.8
0.8
1.6
–
1.8
–14.1
12.0
4.9
1.4
1.9
–
1.7
–14.3
11.5
5.5
n .d.
2.1
–
1.8
–14.7
11.2
4.3
1.7
–14.7
11.1
4.3
1.7
–14.8
11.1
4.4
4a,4e
4a,5
4e,5
5,8
–
–
–
–
–
5,9
–
–
–
–
–
–
5,10
9.5
–11.4
11.4
3.3
2.3
12.5
3.4
–12.3
12.5
3.4
1.2
0.8
6.9
0.9
8.2
–
9.8
9.7
9.6
9.8
9.8
7a,7e
7a,8
–12.1
3.5
2.2
0.7
6.1
–
–12.0
3.6
2.2
<1
–11.4
11.4
3.6
–11.4
11.3
3.5
–12.0
3.5
3.0
0.9
5.5
–
–12.0
3.6
2.1
–
–11.9
3.7
1.2
1.0
6.5
–
–11.5
11.5
3.8
–11.4
11.3
n .d.
n .d.
12.4
n .d.
n .d.
12.4
n .d.
1.0
–11.5
11.5
n .d.
2.2
7e,8
7e,9e
8,9a
1.8
2.0
1.8
6.0
–
12.4
3.5
12.5
5.2
6.0
–
12.5
3.8
12.5
n .d.
–12.5
12.4
n .d.
1.1
8,9e
9a,9e
9a,10
9e,10
10,12
10,14
12,13
12,14
13,14
5′,6′d
5′,6′u
6′u,6′d
9′d,9′u
10′d,11
10′u,11
11′,OH
–
–
–12.8
12.4
3.5
–12.5
12.5
3.6
–
–
–
–12.5
12.5
4.0
–
–
–
–
–
–
–
–
–
–
–
–
n .d.
n .d.
n .d.
n .d.
n .d.
–
1.3
–
–
–
0.7
–
–
n .d.
7.4
–
–
–
0.6
0.5
0.6
7.1
1.0
7.9
–
7.0
1.1
8.1
–
7.1
0.8
8.0
1.1
n .d.
–11.3
–8.4
8.8
3.0
1.4
7.2
0.8
8.0
<0.5
4.1
–11.2
–8.4
n .d.
n .d.
1.6
7.3
1.2
7.6
<0.5
4.3
–11.6
n .d.
n .d.
n .d.
1.6
7.1
7.2
7.0
1.3
0.7
0.7
1.0
8.1
8.2
8.2
8.2
–
1.0
1.0
0.6
–
–
–
–
–
4.5
4.1
4.8
–
–
–
–
–
–11.3
–8.4
n .d.
n .d.
1.5
–11.4
–8.4
8.4
–10.9
–8.5
n .d.
n .d.
1.7
n .d.
9.8
6.3
1.8
n .d.
9.7
6.0
1.8
–12.3
9.2
6.8
1.7
–12.4
9.7
–12.1
7.8
5.9
1.8
6.1
1.9
1.7
1.5
a
Gem in al couplin gs are reported as n egative; n .d. – n ot determ in ed. Ref.24
Collect. Czech. Chem. Commun. (Vol. 65) (2000)

Peptidic Ergot Alkaloids
1767
TABLE IV
Data collection an d refin em en t param eters for 11b
Crystal dim en sion s, m m
0.21 × 0.56 × 0.91
Diffractom eter an d radiation used, Å
En raf–Non ius CAD4, CuKα
λ = 1.54056
Scan tech n ique
Tem perature, K
ω/2θ
293
No. an d θ ran ge of reflection s for lattice param eter
refin em en t, °
20; 38–40
Ran ge of h, k an d l
–27→27, –10→10, –19→19
Stan dard reflection s m on itored in in terval, m in ;
in ten sity fluctuation , %
60; 1.28
Total n um ber of reflection s m easured; 2θ ran ge, °
No. of observed reflection s
Criterion for observed reflection s
Fun ction m in im ized
4 655; 6–110
4 536
I ≥ 1.96σ(I)
w (| F | − | F | )2
o
c
Weigh tin g sch em e
Ch ebych ev polyn om ial ref.25
Param eters refin ed
417
Value of R, wR, an d S
0.0737, 0.0819, an d 0.998
0.002
Ratio of m axim um least-squares sh ift to e.s.d.
in th e last cycle
Maxim um an d m in im um h eigh ts in fin al ∆ρ m ap, e Å–3
0.83, –0.74
Source of atom ic scatterin g factors
In tern ation al Tables for X-Ray
Crystallograph y (ref.26
)
Program s used
CRYSTALS (ref.27), PARST (ref.28),
SIR92 (ref.29
)
Collect. Czech. Chem. Commun. (Vol. 65) (2000)

1768
Cvak et al.:
(3), 9,10-dih ydroergocristin e (4), an d 9,10-dih ydroergotam in e (5). Accordin g to TLC, th e re-
action was com plete after on e 1 h stirrin g below 0 °C givin g rise th e 6′-deoxo derivatives 6,
7, 9, 10, an d 11, respectively (Sch em e 1). Th e reaction provided a sin gle product except for
ergocristin e (2), wh ere 6′-deoxoergocristin in e (8) was detected as a m ajor by-product in addi-
tion to 6′-deoxoergocristin e (7). An excess of h ydride was decom posed with water (20 m l in
200 m l of tetrah ydrofuran ), th e suspen sion form ed was filtered off an d th e filtrate was evap-
orated. Th e residue was subjected to colum n ch rom atograph y on silica gel (dich loro-
m eth an e, TLC m on itorin g). In dividual fraction s were an alysed an d pooled on th e basis of
TLC on silica gel 60 plates (Merck; ch loroform –toluen e–aceton e–eth an ol, 5 : 3 : 2 : 1, detec-
tion by th e Eh rlich reagen t). Fraction s con tain in g desired 6′-deoxo derivatives were pooled,
evaporated an d crystallized from appropriate solven ts. Crystallization of 6′-deoxo-
9,10-dih ydroergotam in e from aceton e or butan -2-on e provided two crystallin e form s;
dih ydrate aceton e solvate pron e to desolvation den oted as 11a (based on NMR an d assay),
an d dih ydrate butan -2-on e solvate den oted as 11b (see crystal structure determ in ation ).
6′-Deoxo-α-ergokryptine (6). Yield 51%, purity 98.7% (HPLC), 98.2% (assay titration ); m .p.
171–177 °C (eth yl acetate–h exan e), [α ]2D0 10.9. FAB MS, m/z: 562 [M + H]+; EI MS: 295 (5),
294.1940 (23,
C16H26N2O3), 280 (16), 279.1710 (100, C15H23N2O3), 267.1373 (14,
C
16H17N3O), 223 (6), 221 (10), 207 (6), 197 (5), 196 (18), 195.1498 (75, C11H19N2O), 180
(5), 111 (13), 110 (20), 97 (5), 84 (11), 83 (27), 82 (7), 71 (9), 70 (19), 69 (6), 57 (11), 55
(18), 43 (36), 42 (8), 41 (21), 27 (6), 18 (6).
C23
C22
O2
C15
N2
C24
C26
C17
C21
C25
N3
C5
C6
O5
N5
C4
C16
C3
C2
C18
O1
C7
C8
N4
C27
C20
C1
C19
C9
O3
C14
C33
C28
C29
C10
N1
C32
C13
C11
C12
C31
C30
FIG. 1
Ortep30 drawin g of 11b with th e n um berin g system used for th e X-ray data
Collect. Czech. Chem. Commun. (Vol. 65) (2000)

Peptidic Ergot Alkaloids
1769
a
x
z
0
y
b
y
x
0
z
FIG. 2
Packin g sch em e of 11b: a Projection alon g y axis; b detailed view of a discrete “pillar”
(dash ed lin es represen t h ydrogen bon ds)
Collect. Czech. Chem. Commun. (Vol. 65) (2000)

1770
Cvak et al.:
6′-Deoxo-α-ergocristine (7). Yield 42%, purity 98.2% (HPLC), 99.1% (assay titration ); m .p.
206–218 °C (aceton e), [α ]2D0 –177.7. FAB MS, m/z: 596 [M + H]+; EI MS: 328.1784 (31,
C
19H24N2O3), 314 (18), 313.1535 (100, C18H21N2O3), 267.1370 (39, C16H17N3O), 230 (13),
229.1330 (68, C14H17N2O), 224 (7), 223 (10), 221 (22), 207 (16), 196 (9), 181 (8), 180 (14),
167 (6), 154 (10), 117 (12), 111 (10), 91 (25), 83 (20), 82 (13), 70 (9), 55 (11), 43 (16), 42 (9),
41 (12).
R1
OH
O
H
N
CO N
H
H
N
O
10'
H R2
9'
8'
N
H
R1
CH3
OH
11'
18
O
H
N
CO N
2' 12'
6, 7
H6'
LiAlH4
H
N
9
8
7
3'
HN
+
O
5'
12
O
THF, -5 oC
H R2
11
N
H
13
14
10
CH3
17
R1
OH
5
16
O
4
H
N
CO N
H
15
H
3
N
1, 2
HN
2
O
H R2
N
H
CH3
8
HN
R1
CO N
H
R1
CO N
H
OH
OH
O
O
H
N
H
N
H
H
N
LiAlH4
N
O
H
H
O
O
H R2
H R2
N
H
N
H
THF, -5 oC
CH3
CH3
9, 10, 11
HN
3, 4, 5
HN
R2
R1
1, 3, 6, 9
CH(CH3)2
CH(CH3)2
CH3
CH2CH(CH3)2
CH2Ph
2, 4, 7, 8, 10
5, 11
CH2Ph
SCHEME 1
Collect. Czech. Chem. Commun. (Vol. 65) (2000)

Peptidic Ergot Alkaloids
1771
6′-Deoxo-α-ergocristinine (8). Yield 24%, purity 95.0% (HPLC); m .p. 230–235 °C (aceton e),
[α ]2D0 360.3. FAB MS, m/z: 596 [M + H]+; EI MS: 328.1772 (30, C19H24N2O3), 314 (18),
313.1553 (100,
C18H21N2O3), 267.1372 (45, C16H17N3O), 230 (16), 229.1330 (72,
C
14H17N2O), 223 (12), 221 (25), 207 (15), 196 (11), 180 (17), 167 (7), 154 (12), 117 (14), 111
(15), 91 (28), 83 (24), 82 (13), 70 (11), 55 (12), 43 (17), 42 (10), 41 (14).
6′-Deoxo-9,10-dihydro-α-ergokryptine (9). Yield 68%, purity 98.4% (HPLC), 98.6% (assay ti-
tration ); m .p. 188–194 °C (CH2Cl2), [α ]2D0 15.2. FAB MS, m/z: 564 [M + H]+; EI MS: 294.1942
(17, C16H26N2O3), 280 (17), 279.1713 (100, C15H23N2O3), 269.1518 (30, C16H19N3O), 223
(10), 196 (9), 195.1500 (61, C11H19N2O), 167 (9), 154 (13), 83 (15), 82 (10), 70 (12), 55 (12),
43 (16), 41 (13).
6′-Deoxo-9,10-dihydroergocristine (10). Yield 66%, purity 98.7% (HPLC), 99.0 (assay titra-
tion ); m .p. 222–223 °C (CH2Cl2), [α ]D20 –36.5. FAB MS, m/z: 598 [M + H]+; EI MS: 329 (7),
328.1781 (32, C19H24N2O3), 314 (19), 313.1544 (100, C18H21N2O3), 270 (7), 269.1537 (33,
C
16H19N3O2), 230 (12), 229.1325 (58), 225 (6), 223 (10), 167 (7), 154 (12), 144 (7), 117 (8),
91 (15), 83 (13), 82 (7), 55 (8), 43 (9), 41 (7).
6′-Deoxo-9,10-dihydroergotamine dihydrate acetone solvate (11b). Yield 59%, purity 98.2%
(HPLC), 85.6% (assay titration ); m .p. 189–194 °C (aceton e), [α ]2D0 –41.5. FAB MS, m/z: 596
[M + H]+; EI MS: 301 (11), 300.1500 (59, C17H20N2O3), 269.1534 (18, C16H19N3O), 230.1400
(17, C14H18N2O), 229.1325 (100, C14H17N2O), 167 (4), 154 (6), 111 (10) 91 (15), 83 (15), 74
(11), 55 (13), 43 (10), 41 (13).
RESULTS AND DISCUSSION
Selective reduction of ergopeptin es with LiAlH4 is described. In con trast to
th e previously reported com plete reduction of all th ree carbon yl groups at
70 °C in 4-eth ylm orph olin e16, th e reaction of ergopeptin es with a LiAlH4
suspen sion in THF at –5 °C in an in ert atm osph ere, decom position of th e
un reacted agen s with water, an d ch rom atograph y of th e products provided
selectively 6′-deoxoergopeptin es 6, 7, 9, 10, an d 11. Th is selectivity is a re-
sult of th e low tem perature on ly; n eith er th e reaction tim e n or th e am oun t
of h ydride used h ad an y m arked effect. With ergocristin e (2), 6′-deoxo-
ergocristin in e (8) was detected as a m ajor by-product. It sh ould be n oted,
h owever, th at ergopeptin es, in con trast to 9,10-dih ydroergopeptin es, are
pron e to epim erization an d th us th ese by-products can be expected to vari-
ous exten t also with oth er ergopeptin es.
New derivatives were ch aracterized by a com bin ation of various spectro-
m etric m eth ods. Molecular cation -radicals of peptidic ergot alkaloids are
usually absen t in th e EI spectra, but can be obtain ed usin g FAB ion ization .
Un der EI con dition s, ergot alkaloids un dergo two m ain com petitive cleav-
ages: in to ergolin e an d peptide parts. Th e wh ole ergolin e part of th e m ole-
cule in th e m ass spectra of 9,10-dih ydro derivatives is represen ted by ion
269 (elem en tal com position C16H19N3O); in th e case of 9,10-un saturated
derivatives, th e ion m/z 267 (C16H17N3O) is observed. Ch aracteristic
Collect. Czech. Chem. Commun. (Vol. 65) (2000)

1772
Cvak et al.:
ergolin e low-m ass fragm en ts are m/z 167 (com position C12H9N) an d m/z
154 (C11H8N); see ref.18. Peptide parts of ergocristin e, α-ergokryptin e, an d
ergotam in e derivatives are ch aracterized by ion s m/z 328, 294, an d 300, re-
spectively, th at in turn release th e R1CO–CO species (to give ion s m/z 229,
195, an d 229, respectively) an d th us determ in e th e R1 substitution . With
th e exception of th e ergotam in e derivative, th e peptide ion s of all alkaloids
readily elim in ate th e m eth yl radical (elim in ation from th e acetyl group in
ergotam in e is n ot favoured). Furth er ion s origin atin g from th e peptide parts
of th e m olecules are m/z 111 (an alogous to m/z 125 observed in spectra of
paren t ergopeptin es19) an d th e m/z 70 fragm en t (com position C 4 H +8 ) ch ar-
acterizin g prolin e. Th e absen ce of a carbon yl group at 6′-position dram ati-
cally affected th e fragm en tation of th e correspon din g peptide ion s. In
con trast to α-ergokryptin e sh owin g an exten sive side ch ain losses from th e
piperazin e rin g, th e fragm en tation of its 6′-deoxo derivative led predom i-
n an tly to th e m eth yl-radical loss.
Pseudom olecular ion s of all n ew com poun ds 6–11 foun d in th eir FAB
m ass spectra were by 14 m ass un its lower th an th ose of th e paren t com -
poun ds 1–5. Th e m olecular form ulas (determ in ed in directly as th e sum of
elem en tal com position s of com plem en tary ergolin e an d peptide ion s) con -
firm ed th e loss of on e oxygen atom . Two carbon yl sign als appearin g in th e
13C NMR spectra in stead of th ree in th e paren t com poun ds proved th is
idea. Ch aracteristic sign als of two sp3-h ybridized carbon s attach ed to two
h eteroatom s (C-2′, C-12′) in dicated th e in tact cyclol system . Accordin g to
COSY an d LR COSY experim en ts, th e ergolin e or ergolen e m oieties were
n ot affected by reduction . An exception was th e case of ergocristin e, wh ere
th e secon d reaction product was foun d to be derived from ergocristin in e
th rough its 8-epim erization . Newly form ed m eth ylen e groups (carbon s res-
on atin g at 52–55.5 ppm , Table I) correspon ded to a carbon of th e –CH2N–
type. Proton s H-6′ in com poun ds 6–11 (Table II) exh ibited two addition al
couplin gs wh en com pared with th eir coun terparts in th e paren t alkaloids.
Th e sources of th ese couplin gs were th e m eth ylen e proton s attach ed to th e
above m en tion ed carbon s. Except th eir m utual couplin gs, th ese proton s
h ad n o oth er couplin g partn ers except H-6′. Th erefore, th e reduction took
place at th e secon d am in o acid of 6–11.
Proton s form ed as th e result of th e keto group reduction exh ibit m ag-
n etic n on -equivalen ce (0.864–1.074 ppm , Table II) an d sim ilar m ultiplicity
(Table III): on e sm all an d on e m edium couplin g. Th e ch an ges at C-5′ are
also reflected by th e couplin gs of H-5′ to its n eigh bours in th e side ch ain (1:
6.0, 7.6; 2: 4.9, 7.0; 3: 5.4, 8.1; 4: 5.8, 6.1; 5: 5.8, 6.3; 6: 8.4, 6.6; 7: 11.5,
3.5; 8: 11.7, 3.6; 9: 8.3, 6.7; 10: 11.0, 4.3; 11: 11.0, 4.4 Hz). Th e resultin g
Collect. Czech. Chem. Commun. (Vol. 65) (2000)

Peptidic Ergot Alkaloids
1773
con form ation is m arkedly differen t from th at of paren t com poun ds. Th e
observed couplin gs correspon d to on e antiperiplanar- an d on e gauche-ori-
en ted proton . A crucial sign ifican ce for th e poten tial biological activity
m igh t h ave th e predom in an t population of con form ers with differen t ori-
en tation of th e ben zyl group of 7, 10, an d 11 in solution , with respect to 2,
4, an d 5 (see footn ote to Table III). Noteworth y, th e sam e con form ation is
foun d in th e solid state (see Table V, χ 13 , an d Fig. 1). Th e effect of C=O
group reduction is also m an ifested on th e prolin e rin g atom s. Th e m ost
TABLE V
Com parison of selected torsion an gles in 6′-deoxo-9,10-dih ydroergotam in e (11b ) an d
ergotam in e tartrate bis(eth an ol) solvate23 (11)
Torsion an glea
Piperazin e rin g
11b
12
N4C19C20N5
C19C20N5C24
C20N5C24C25
N5C24C25N4
C24C25N4C19
C25N4C19C20
N4C19C27C28
C19C20N5C21
C20N5C24C23
N5C24C23C22
C21C22C23C24
N5C21C22C23
C22C21N5C24
C21N5C24C23
Ψ3
ω3
θ4
0.3(8)
–1.6(9)
–48.9(4)
62.7(4)
–24.6(9)
49.0(7)
–64.8(4)
54.8(4)
Ψ4
–56.5(7)
31.1(8)
–50.7(4)
46.5(4)
Ph en ylalan in e
Prolin e rin g
χ 31
–68.6(8)
–174.8(6)
–150.3(5)
–37.7(7)
38.6(7)
–171.4(3)
–179.9(4)
168.9(3)
–30.0(4)
4.9(5)
χ 41
χ 43
χ 43
χ 44
χ 45
–24.8(8)
1.0(8)
22.0(5)
–42.0(4)
45.1(4)
23.6(7)
a
Den otation of torsion an gles by Greek letters refers to th e usual peptide n om en clature an d
does n ot con sider subsequen t m odification of a particular am in o acid.
Collect. Czech. Chem. Commun. (Vol. 65) (2000)

1774
Cvak et al.:
m arked results are th e large upfield sh ift of H-11′ (1.55–1.65 ppm ) an d in -
creased m agn etic n on equivalen ce of H-8′ proton s (1.03–1.10 ppm ) with re-
spect to th e paren t com poun ds (0.06–0.11 ppm ). Un fortun ately, because of
exten sive sign al overlap, th e extraction of all vicin al couplin g con stan ts de-
fin in g th e prolin e rin g con form ation was n ot possible from th e NMR data.
Sligh t ch an ges in th e carbon ch em ical sh ifs were also foun d at atom s C-2′
(–0.96 to –1.51 ppm ) an d C-12′ (1.7–2.1 ppm ).
Crystal structure determ in ation of 11b (crystallograph ic data for th e
structure reported in th is paper h ave been deposited with th e Cam bridge
Crystallograph ic Data Cen tre as supplem en tary publication n um ber
CCDC-147347. Copies of th e data can be obtain ed free of ch arge on appli-
cation to CCDC, e-m ail: deposit@ccdc.cam .ac.uk.), a represen tative m em ber
of th e series, provided an addition al con firm ation of th e m olecular struc-
ture. Wh ereas th e con form ation of th e ergolin e m oiety is n early iden tical
in 6′-deoxo-9,10-dih ydroergotam in e as well as in all oth er 9,10-dih ydro-
ergopeptin es1,20–22, reduction of th e carbon yl group affected dram atically
th e overall con form ation an d puckerin g of th e cyclol m oiety. Th e m ost in -
terestin g ch an ges are sum m arized in Table V in com parison with
ergotam in e tartrate23. Obviously, th e differen t puckerin g of th e piperazin e
rin g is associated with th e sp2→sp3 h ybridization of th e C20 atom due to
th e tran sform ation of th e keto group in to m eth ylen e. In con trast to NMR,
X-ray data m ake it possible to obtain also a detailed in form ation about th e
prolin e con form ation (Table V). Th e h ydrogen bon d n etwork (Fig. 2a)
form s in terestin g “pillars” in th e y direction (see Fig. 2b for detail), repre-
sented by N1–H611···O3 [–x – 1/2, y – 1/2, –z + 1] (148° angle, 2.954(3) Å sepa-
ration) and a bridge-like form ation N3–H631···O80–H801···N5 [x, y – 1, z]
(173°, 2.868(4)
Å
for N3–H631–O80 an d 166°, 2.980(6)
Å
for
O80–H801–N5). Note th e dash ed H611···O3 lin es in Fig. 2a represen tin g
sets of zig-zag bon ds as sh own in Fig. 2b. Th e form ation of butan -2-on e
solvate is expected to be respon sible for th e stability an d growth of th e
crystal. Most of th e com poun ds described in th is work form un solvated
crystals n ot suitable for X-ray an alysis. Replacin g C26 with a larger
substituent m ay also destabilize the “bridge”. The second water m olecule is at-
tached to N2 via O90–H901···N2 (164°, 2.826(5) Å). An in tram olecular h y-
drogen bon d O5–H551···O1 (153°, 2.724(4) Å) is typical of m ost
ergopeptin es. No acceptable con tact was foun d for butan -2-on e.
Th e n ew com poun ds exh ibited receptor activities (dopam in e, seroton in e,
n oradren alin e) sim ilar to th ose of paren t com poun ds but th ey were m ore
lipoph ilic. A detailed study of th eir ph arm acological properties will be re-
ported elsewh ere.
Collect. Czech. Chem. Commun. (Vol. 65) (2000)

Peptidic Ergot Alkaloids
1775
This research was supported by the Ministry of Education, Youth and Sports of the Czech Republic
(research project No. CEZ:MSM 223100002).
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1. Čejka J., Kratochvíl B., Jegorov A., Cvak L.: Collect. Czech. Chem. Commun. 2000, 65, 1329.
2. Stoll A., Hofmann A. in: The Alkaloids (R. H. F. Manske and H. L. Holmes, Eds), Vol. 8,
p. 725. Academic Press, New York 1965.
3. Stadler P. A., P. Stütz in: The Alkaloids (R. H. F. Manske and H. L. Holmes, Eds), Vol. 15,
p. 1. Academic Press, New York 1975.
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