(1H, d, 2J3-endo,3-exo 16.5, 3-Hendo), 1.90 (1H, t, 3J4,3-exo and 3J4,5-exo
1.58–1.69 (1H, td, 2J6-exo,6-endo and 3J6-exo,5-exo 12.6, 3J6-exo,5-endo 4.0,
3
3
4.5, 4-H), 2.26 (1H, complex octet, Jβ-CH,Me 6.5 and Jβ-CH,α-CH
6-Hexo), 1.75–1.87 (1H, complex m, 5-Hexo), 1.85 (1H, d,
7.2, Val β-CH), 2.29 (1H, complex overlapping br dt, 2J3-exo,3-endo
2J3-endo,3-exo 16.9, 3-Hendo), 1.91 (1H, t, J4,3-exo and J4,5-exo 4.5,
4-H), 2.01–2.15 (1H, complex m, Ile β-CH), 2.31 (1H, over-
lapping ddd, 2J3-exo,3-endo 16.9, 3J3-exo,4 4.5, 4J3-exo,5-exo 2.8, 3-Hexo),
3 3
3
4
3
16.5, J3-exo,4 4.5, J3-exo,5-exo 3.7, 3-Hexo), 3.59 (1H, d, Jα-CH,β-CH
7.2, Val α-CH), 3.65 (3H, s, CH3O2C); δC(75.5 MHz; CDCl3)
11.3 (C-10), 18.5 (Val γ-Mea), 18.8 (C-9), 19.5 (Val γ-Meb),
19.53 (C-8), 27.3 (C-5), 31.5 (Val β-CH), 31.8 (C-6), 35.8 (C-3),
43.9 (C-4), 46.5 (C-7), 51.6 (OCH3), 54.3 (C-1), 71.2 (Val
α-CH), 172.5 (C᎐O), 184.8 (C᎐N); m/z (EI) 265 (7%, Mϩ), 237
3
3.667 (1H, d, Jα-CH,β-CH 7.9, Ile α-CH), 3.67 (3H, s, CH3O2C);
δC(75.5 MHz; CDCl3) 11.1 (Ile δ-Me), 11.3 (C-10), 15.7 (Ile
γ-Me), 18.9 (C-9), 19.5 (C-8), 24.9 (Ile γ-CH2), 27.3 (C-5), 31.9
(C-6), 35.8 (C-3), 37.8 (Ile β-CH), 43.9 (C-4), 46.7 (C-7), 51.6
᎐
᎐
(4, M Ϫ 28), 222 (57, M Ϫ C3H7), 206 (100, M Ϫ CO2Me), 162
(4), 150 (4, M Ϫ C6H11O2ϩ), 115 (7, C6H11O2ϩ), 108 (3, C8H12ϩ),
95 (14, C7H11ϩ), 83 (13), 69 (12), 59 (17), 55 (18).
(OCH ), 54.4 (C-1), 70.3 (Ile α-CH), 172.6 (C᎐O), 185.1 (C᎐N);
᎐ ᎐
3
m/z (EI) 279 (6%, Mϩ), 264 (4, M Ϫ CH3), 251 (22, M Ϫ 28),
223 (68, M Ϫ C4H8), 222 (70, M Ϫ C4H9), 220 (100, M Ϫ CO2-
Me), 208 (9), 180 (6), 163 (18), 150 (10, M Ϫ C7H13O2), 129 (11,
C7H13O2ϩ), 108 (8, C8H12ϩ), 95 (25, C7H11ϩ), 83 (16), 69 (53), 59
(33), 55 (39).
Methyl N-[(1R,2E,4R)-bornan-2-ylidene]-(S)-leucinate 5d
{methyl (S)-4Ј-methyl-2Ј-([1R,2E,4R]-1,7,7-trimethylbicyclo-
[2.2.1]heptan-2-ylideneamino)pentanoate}. Methyl (S)-leucinate
hydrochloride 4d (908 mg, 5 mmol) was used in the general pro-
cedure using DCM (20 cm3) as co-solvent and gave the product,
methyl N-[(1R,2E,4R)-bornan-2-ylidene]-(S)-leucinate 5d,
as a pale yellow oil (631 mg, 45%), [α]D20 Ϫ102.4 (c 0.50 in
DCM) [Found: m/z (EI) Mϩ, 279.22014. Calc. for C17H29NO2:
M, 279.21983, deviation 1.1 ppm; (CI, NH3) MHϩ, 280.22770.
Calc. for C17H30NO2: m/z, 280.22763, deviation 0.3 ppm];
νmax(film)/cmϪ1 2960s, 2876s, 1747s (C᎐O str), 1685s (C᎐N str),
Methyl N-[(1R,2E,4R)-bornan-2-ylidene]-(S)-serinate 5f
{methyl (S)-3Ј-hydroxy-2Ј-([1R,2E,4R]-1,7,7-trimethylbicyclo-
[2.2.1]heptan-2-ylideneamino)propanoate}. Methyl (2S)-serinate
hydrochloride 4f (778 mg, 5 mmol) was used in the general
procedure using MeOH (20 cm3) as co-solvent and gave the
product, methyl N-[(1R,2E,4R)-bornan-2-ylidene]-(S)-serinate
5f, as a clear oil (836 mg, 66%) [Found: m/z (EI) M, 253.16779.
Calc. for C14H23NO3: M, 253.16779, deviation
0 ppm];
᎐
᎐
νmax(film)/cmϪ1 3432vbr m (O-H str), 2957s, 2876m, 1741s (C᎐O
1468m, 1442m, 1389m, 1371m, 1272m, 1242m, 1197m, 1170m,
᎐
str), 1679s (C᎐N str), 1437m, 1390m, 1371m, 1200s, 1171s,
1142m; δH(300 MHz; CDCl3) 0.73 (3H, s, C-8 Me), 0.82 (3H, d,
᎐
3
3JMeα,γ-CH 6.6, Leu δ-Mea), 0.915 (3H, d, JMeb,γ-CH 6.6, Leu
1052s; δH(300 MHz; CDCl3)¶¶ 0.70 and 0.77 (3H, s, C-8 Me),
0.88 (3H, s, C-9 Me), 0.93 and 0.94 (3H, s, C-10 Me), 1.12–1.21
δ-Meb), 0.92 (3H, s, C-9 Me), 0.98 (3H, s, C-10 Me), 1.13–1.23
2
3
2
3
(1H, overlapping ddd, J5-endo,5-exo 12.8, J5-endo,6-endo 9.0 and
(1H, overlapping ddd, J5-endo,5-exo 12.6, J5-endo,6-endo 9.1 and
3J5-endo,6-exo 4.1, 5-Hendo), 1.35–1.45 (1H, overlapping ddd,
3J5-endo,6-exo 4.1, 5-Hendo), 1.23–1.33 and 1.35–1.45 (1H, 2 × over-
lapping ddd, J6-endo,6-exo 12.7, J6-endo,5-endo 9.0, J6-endo,5-exo 4.5,
6-Hendo), 1.58–1.70 (1H, br ddd, 2J6-exo,6-endo 12.7, 3J6-exo,5-exo 12.0
and 3J6-exo,5-endo 4.1, 6-Hexo), 1.75–1.86 (1H, complex m, 5-Hexo),
2
3
3
3
3
2J6-endo,6-exo 13.5, J6-endo,5-endo 9.1, J6-endo,5-exo 4.5, 6-Hendo), 1.49–
1.89 (5H, series of overlapping multiplets, partially discernable
as: 1.49–1.62, complex m, 6-Hexo; 1.63–1.71, complex m, Leu
γ-CH; 1.68–1.82, m, 3J 8.6 and 5.2, Leu β-CH2; 1.78–1.89,
complex m, 5-Hexo), 1.88 (1H, d, 2J3-endo,3-exo 16.8, 3-Hendo), 1.92
(1H, t, 3J4,3-exo and 3J4,5-exo 4.5, 4-H), 2.33 (1H, overlapping ddd,
2
1.78 and 1.84 (1H, d, J3-endo,3-exo 16.8, 3-Hendo), 1.90 (1H, t,
3J4,3-exo and 3J4,5-exo 4.4, 4-H), 2.32 (1H, br ddd, 2J3-exo,3-endo 16.8,
3J3-exo,4 4.4, 4J3-exo,5-exo 3.0, 3-Hexo), 3.11 (1H, br s, OH), 3.64 and
3.66 (3H, s, CH3O2C), 3.83 [1H, ddd, 2Jβ-CHa,CHb 11.0, 3Jβ-CHa,α-CH
3
4
2J3-exo,3-endo 16.8, J3-exo,4 4.5, J3-exo,5-exo 2.8, 3-Hexo), 3.67 (3H, s,
3
2
3
3
5.5, J
1.5, Ser β-CHaCHb], 3.89 [1H, ddd, Jβ-CHaCHb
11.0, Jβ-CHb,α-CH 5.0, J(β-CH -OH) 1.5, Ser β-CHaCHb], 4.22 (1H,
CH3O2C), 3.97 (1H, dd, Jα-CH,β-CHa 8.6, Jα-CH,β-CHb 5.2, Leu
α-CH); δC(75.5 MHz; CDCl3) 11.3 (C-10), 18.9 (C-9), 19.5
(C-8), 21.6 (Leu δ-Mea), 23.3 (Leu δ-Meb), 24.7 (Leu γ-CH),
27.3 (C-5), 31.8 (C-6), 35.7 (C-3), 42.1 (Leu β-CH2), 43.9 (C-4),
46.7 (C-7), 51.7 (OCH3), 54.1 (C-1), 62.6 (Leu α-CH), 173.2
(C᎐O), 184.7 (C᎐N); m/z (EI) 279 (4.5%, Mϩ), 264 (9,
(β-CH2-OH)
3
3
2
3
3
dd, Jα-CH,β-CHa 5.5, Jα-CH,β-CHb 5.0, Ser α-CH); δC(75.5 MHz;
CDCl3) 11.18 and 11.24 (C-10), 18.8 and 19.0 (C-9), 19.3 and
19.5 (C-8), 27.2 and 27.3 (C-5), 31.7 and 32.3 (C-6), 36.0 and
36.3 (C-3), 43.81 and 43.84 (C-4), 46.8 and 47.6 (C-7), 51.93
and 51.98 (OCH3), 54.43 and 54.46 (C-1), 63.6 and 63.7 (Ser
β-CH ), 65.0 and 65.2 (Ser α-CH), 171.07 and 171.14 (C᎐O),
᎐
᎐
M Ϫ CH3), 251 (28, M Ϫ 28), 236 (17, M Ϫ C3H7), 223 (100,
M Ϫ C4H8), 220 (90, M Ϫ CO2Me), 208 (12), 194 (11), 178 (12),
163 (19.5), 150 (12, M Ϫ C7H13O2), 136 (6), 129 (6, C7H13O2ϩ),
108 (8, C8H12ϩ), 95 (26, C7H11ϩ), 83 (35), 69 (35), 55 (27); m/z
(CI, NH3), 280 (100%, MHϩ), 264 (2, M Ϫ CH3), 251 (8,
M Ϫ 28), 236 (1, M Ϫ C3H7), 220 (21, M Ϫ CO2Me), 208 (1),
152 (2), 95 (1, C7H11ϩ).
᎐
2
188.2 and 188.6 (C᎐N); m/z (EI) 253 (3%, Mϩ), 238 (3,
᎐
M Ϫ CH3), 223 (M Ϫ H2CO), 222 (100, M Ϫ CH2OH), 208 (4),
194 (57.5, M Ϫ CO2Me), 164 (37), 136 (13.5, M Ϫ C4H7NO3),
108 (25.2, C8H12ϩ), 95 (78.5, C7H11ϩ), 83 (57), 69 (37), 55 (39).
Diethyl N-[(1R,2E,4R)-bornan-2-ylidene]-(S)-glutamate 5g
{diethyl
(S)-2Ј-([1R,2E,4R]-1,7,7-trimethylbicyclo[2.2.1]-
Methyl
N-[(1R,2E,4R)-bornan-2-ylidene]-(2ЈS,3ЈS)-iso-
heptan-2-ylideneamino)pentanedioate}.
Diethyl (S)-
leucinate 5e {methyl (2ЈS,3ЈS)-3Ј-methyl-2Ј-([1R,2E,4R]-1,7,7-
trimethylbicyclo[2.2.1]heptan-2-ylideneamino)pentanoate}.
Methyl (2S,3S)-isoleucinate hydrochloride 4e (908 mg, 5 mmol)
was used in the general procedure using DCM (20 cm3) as co-
solvent and gave the product, methyl N-[(1R,2E,4R)-bornan-
2-ylidene]-(2ЈS,3ЈS)-isoleucinate 5e, as a clear oil (908 mg,
65%), [α]D27 Ϫ149.4 (c 0.32 in DCM) [Found: m/z (EI) Mϩ,
279.22039. Calc. for C17H29NO2: M, 279.21983, deviation 1.9
glutamate hydrochloride 4g (1.20 g, 5 mmol) was used in the
general procedure using DCM (20 cm3) as co-solvent and gave
the product, diethyl N-[(1R,2E,4R)-bornan-2-ylidene]-(S)-
glutamate 5g, as a clear oil (1.29 g, 76%), [α]D26 Ϫ142.4 (c 0.50 in
DCM) [Found: m/z (EI) Mϩ, 337.22574. Calc. for C19H31NO4:
M, 337.22531, deviation 1.3 ppm]; νmax(film)/cmϪ1 2962s,
2886m, 1739s (C᎐O str), 1685s (C᎐N str), 1448m, 1374m,
1254m, 1180s; δH(300 MHz; CDCl3) 0.71 (3H, s, C-8 Me), 0.89
(3H, s, C-9 Me), 0.95 (3H, s, C-10 Me), 1.11–1.23 (1H,
᎐
᎐
ppm]; νmax(film)/cmϪ1 2960s, 2876m, 1743s, 1732sh (C᎐O str),
1679m (C᎐N str), 1453m, 1436m, 1388w, 1374w, 1261m,
᎐
᎐
1194m, 1171m, 1139m; δH(300 MHz; CDCl3) 0.73 (3H, s, C-8
Me), 0.84 [3H, t, 3J(Me,γ-CH ) 7.2, Ile δ-Me], 0.87 (3H, d, 3JMe,β-CH
6.4, Ile γ-Me), 0.915 (3H2, s, C-9 Me), 0.98 (3H, s, C-10 Me),
1.01–1.12 (1H, complex m, Ile γ-CHaHb), 1.11–1.20 (1H, over-
lapping ddd, 2J5-endo,5-exo 12.2, 3J5-endo,6-endo 9.1 and 3J5-endo,6-exo 4.0,
¶¶ Spectroscopic evidence for this homogeneous compound indicates
the existence of two conformers. This may be due to conformational
isomerism involving the amino acid side-chain or the geometry of
the CN double bond. Since NOE studies and temperature-dependence
studies were not carried out, a distinction between these two possi-
bilities cannot be made. The explanation is likely to reside in an
equilibrium between hydrogen-bonded and non-hydrogen-bonded
conformers.
2
5-Hendo), 1.29–1.40 (1H, overlapping ddd, J6-endo,6-exo 12.6,
3
3J6-endo,5-endo 9.1, J6-endo,5-exo 4.2, 6-Hendo), 1.42–1.56 [1H, dqd,
3
3
2Jγ-CHa,CHb 13.2, J(γ-CH
7.2, J(γ-CH ,β-CH) 3.8, Ile γ-CHaHb],
,Me)
2
2
J. Chem. Soc., Perkin Trans. 1, 2001, 248–260
255