5. Chiroptical properties of compounds containing CDO groups |
185 |
O
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R |
14 |
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8 R |
O |
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O |
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(31) |
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(32) |
R = H |
−0.28 (317), +0.36 (283) |
−0.90 (302) |
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R = CH3 |
−0.12 (319), +1.50 (289) |
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R = OH |
−0.22 (319), +1.04 (288) |
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R = OAc |
−0.11 (320), +0.96 (280) |
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OH |
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R = CH2 OH |
−0.10 (323), +1.13 (292) |
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R = CH2 OAc |
−0.10 (323), +1.22 (289) |
A |
B |
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O
(33)
−0.31 (315), +0.36 (283)
O |
O |
(34) |
(35) |
−0.34 (305), +0.12 (272) |
−0.12 (320), +1.59 (290) |
and twist forms with variable ratios. This equilibrium was affected by minor changes at remote positions and by the polarity of the solvent. An increase of the steric bulkiness of the 8ˇ-substituent increased the A-ring twist population. Introduction of an 8˛-substituent in 33 decreased the flexibility of the B-ring, thus increasing the A-ring chair population120.
X-ray crystallographic analysis revealed that methyl cis-tetrahydro-˛- (36) and -ˇ- santoninate (37) have a nonsteroid decalone conformation in the solid state. Furthermore, positive Cotton effects shown by both cis-fused decalone analogues indicated the presence of such nonsteroid conformation (38) in solution, in accord with the octant rule121.
186 |
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Stefan E. Boiadjiev and David A. Lightner |
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R1 |
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R2 |
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O |
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H |
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R1 |
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OH |
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R2 |
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OH |
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O |
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(36) R1 = CH3 , R2 = CO2 CH3 |
+0.67 (284), +0.78 (213) |
(38) |
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(37) R1 = CO2 CH3 , R2 = CH3 |
+0.58 (284)12 1 |
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R1 |
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O |
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R2 |
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H |
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O |
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O |
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R1 = H, R2 = α-CH3 |
+0.83 (285), |
+1.03 (215) |
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R1 = H, R2 = β-CH3 |
+0.91 (285), |
−0.72 (215) |
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R1 = OH, R2 = α-CH3 |
+0.64 (282), |
+1.33 (215) |
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R1 = OH, R2 = β-CH3 |
+0.66 (283), |
−0.59 (220)12 2 |
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O |
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H |
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O |
H |
O |
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O |
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H |
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O |
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O |
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R3 |
AcO |
O |
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R1 |
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O |
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O |
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O |
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O |
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CH2 OR2 |
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(39) |
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(40) |
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1 |
R |
2 |
3 |
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−3.14 (299), +4.26 (242)12 6 |
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R |
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R |
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H |
H |
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H |
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−0.89 (299)12 3 |
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H |
Ac |
H |
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−0.51 (300), −0.40 (225)12 3 ,12 4 |
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OH |
H |
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H |
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−0.87 (302)12 5 |
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OH |
Ac |
H |
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−0.52 (301)12 5 |
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10β-OH OAc |
Ac |
OH |
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−0.71 (298), −0.62 (225)12 6 |
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5. Chiroptical properties of compounds containing CDO groups |
187 |
O H
O
AcO |
O |
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O
O
(41)
+1.74 (296), −0.65 (252)12 6
O H
O
AcO |
O |
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O O
(43)
+2.29 (288), −3.77 (232)12 6
O |
O |
H |
O |
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O |
AcO |
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O |
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O |
O |
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(42) |
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−2.20 (289), +2.30 (225)12 6 |
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O |
O |
H |
O |
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O |
AcO |
H |
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O |
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O |
O |
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O |
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(44) |
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+0.18 (320), |
+0.22 (308), |
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+0.10 (300), |
−0.26 (276)12 6 |
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New diterpenoids belonging to neo-clerodane type (39), some having an unusual neo- clerodane rearranged skeleton with eight-membered ketone ring (40 44), were recently described126.
O
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O |
O |
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H |
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O |
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H |
O |
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O |
H |
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O |
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O |
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O |
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O |
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O |
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O |
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O |
OH |
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OAc |
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CH2 OAc |
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CH2 OAc |
|
+0.93 (303)12 7 |
−2.00 (295)12 7 |
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+1.98 (298)12 8 |
|
188 |
Stefan E. Boiadjiev and David A. Lightner |
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H |
O |
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O |
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H |
O |
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H |
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O |
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AcO |
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O |
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O |
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AcO |
OAc |
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O |
OH |
R |
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H |
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OAc |
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R = H sh−0.20 (312), |
−0.51 (293), |
−0.06(250) |
+1.95 (290)13 0 |
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R = OH sh−0.23 (315), |
−0.57 (295), |
−0.08 (252)12 9 |
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O |
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O |
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O |
O |
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R1 |
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O |
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R4 |
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OH
+0.58 (310), −0.10 (269)13 1
O
O
H
−0.15 (305)13 2
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H |
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R3 |
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R2 |
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R1 |
R2 |
R3 |
R4 |
|
(45) OH |
OH |
OAc |
OH |
−0.73(314)132 |
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−0.75(312)133 |
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H |
OH |
OAc |
OH |
−0.97(300)132 |
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H |
OH |
OAc |
H |
−1.94(303)132 |
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−2.71(312)133 |
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H |
OAc |
OH |
OH |
−1.67(305)132 |
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H |
OAc |
H |
OH |
−0.18(305)132 |
|
H |
H |
H |
OH |
−0.27(305)132 |
The absolute stereochemistry of forskolin (45) and of the C 6 and C 7 dibenzoyl derivative (46) was unequivocally assigned by applying the exciton chirality method, thus placing R3 (OAc in 45) substituent at ˇ-position134.
CD data for n ! Ł Cotton effect of D:A-friedo-oleanones (47 51) have been interpreted on the basis of the octant rule, with the prediction that the D and E rings adopt a boat-boat conformation for 48 and 50138.
Intermediate-intensity positive n ! Ł Cotton effects (all in dioxane) of the 3- oxotriterpenoids 54, 57 59 were attributed to an A-ring chair-boat conformational equilibrium. The contribution of the boat form (like in 2ˇ-methyl model derivatives 53 and 56) was estimated to be ca 30%140.
5. Chiroptical properties of compounds containing CDO groups
O
O |
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O |
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OH |
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H |
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H |
H |
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R1 |
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H |
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OBz |
R2 |
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OBz |
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O |
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(46)
+15.18 (239), −2.42 (221)134
OH
H
O
RO |
OH |
O O
OR
R = H +1.44 (287)
R = Ac +0.30 (280)136
HO
O
H
H H
O
R3 |
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R1 |
R2 |
R3 |
|
H |
H |
H |
−2.68(290)135 |
H |
OAc |
H |
−1.47(300)135 |
OAc |
H |
H |
−2.36(298)135 |
H |
H |
OAc |
−3.17(300)135 |
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OH |
R |
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OH |
OH
R = H +1.60 (287)
R = OH +1.03 (290)136
−2.18 (285)137
189
OH
190 |
Stefan E. Boiadjiev and David A. Lightner |
R5
R6
R1
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R2 |
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R4 |
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R3 |
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R1 |
R2 |
R3 |
R4 |
R5 |
R6 |
∆ε(CHCl3 ) |
λmax |
(47) |
O |
H2 |
H2 |
H2 |
H2 |
H2 |
−1.17 |
293 |
(48) |
H2 |
O |
H2 |
H2 |
H2 |
H2 |
−3.46 |
294 |
(49) |
H2 |
H2 |
O |
H2 |
H2 |
H2 |
+2.49 |
293 |
(50) |
H2 |
H2 |
H2 |
H2 |
O |
H2 |
+8.98 |
295 |
(51) |
H2 |
H2 |
H2 |
H2 |
H2 |
O |
+2.38 |
294 |
O
HO
OH
OH
HO
−5.36 (284), −14.51 (213)139
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H |
O |
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H |
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R2 |
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R |
2 |
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CN |
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R1 |
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R1 |
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O |
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O |
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(52) |
R1 = CH3 , R2 = H |
−0.60(293) |
(55) |
R1 |
= CH3 , R2 = H |
−0.71(292) |
|
(53) |
R1 = H, R2 = CH3 |
+3.65(294) |
(56) |
R1 |
= H, R2 = CH3 |
+3.85(291) |
|
(54) |
R1 = R2 = H |
+0.76(293) |
(57) |
R1 |
= R2 = H |
+0.55(292) |
|
5. Chiroptical properties of compounds containing CDO groups
O
H H
O |
|
O |
|
(58) |
+0.63 (293) |
(59) |
+0.73 (293) |
|
HO |
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R2 |
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OH |
O
R1 |
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O |
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R1 |
= O, R2 = |
OH |
+0.35 |
(293)141 |
+0.37 (292)141 |
|
H |
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R1 |
= H,H, R2 = O |
−0.60 |
(287)141 |
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R |
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OR |
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R |
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OR |
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HO |
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Br |
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H |
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O |
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O |
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R = bond |
−2.70 (292) |
R = H |
|
−2.11 |
(292) |
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R = HO − |
−1.43 (300) |
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O− |
−2.88 (292)142 |
R = Me2 C |
|
−1.95 |
(291)142 |
R = Me2 C |
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O−
191
Br
192 |
Stefan E. Boiadjiev and David A. Lightner |
OH
OH
|
O |
|
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HO |
|
H |
|
H |
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O |
O |
|
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−2.04 (293)142 |
−1.79 (292)142 |
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OH |
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R |
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OH |
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R |
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O |
O |
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H |
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H |
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O |
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O |
−2.64 (292)142 |
R = bond |
−2.95 (291) |
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R = HO− |
−3.51 (294)142 |
H |
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H |
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R1 |
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R1 |
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H |
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H |
R2 |
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R2 |
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R1 = CH2 , R2 = O |
|
R1 = CH2 , R2 = O |
|
||
+0.75 (317), |
+1.22 (307), |
+0.67 (319), |
+1.23 (309), |
||
+1.22 (298), |
−6.10 (212)143 |
+1.11 (294), |
+11.0 (198)143 |
||
R1 = O, R2 = α-OAc,β-H |
R1 = O, R2 = α-OAc,β-H |
||||
|
|
sh +0.07(315), sh +0.17 (302), |
+2.72 (292), |
+0.80 (205)143 |
|
+0.28 (287), |
−1.30 (199)143 |
R1 = O, R2 = α-H,β-OAc |
|||
R1 = O, R2 = α-H,β-OAc |
|||||
+0.06 (319), |
+0.01 (306), |
+2.23 (288)143 |
|||
+0.13 (278), |
−1.60 (201)143 |
|
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||
5. Chiroptical properties of compounds containing CDO groups |
193 |
HO
HO O
H
HO
H
HO
H
OH
−2.48 (295)144
R2 |
R2 |
O |
O |
H |
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H |
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R1 |
|
R1 |
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|
R2 = CH(CH3 )CH2 CH2 CO2 CH3 |
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|
||
R1 = H |
−0.82 (292) |
R1 = CH3 |
+1.27 (289) |
||
R1 = CH3 |
−0.39 (285) |
R1 = (CH3 )2 |
−0.27 (309)145 |
||
R1 = (CH3 )2 |
−0.94 (299)145 |
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O |
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O |
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C8 H17 |
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BnO |
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H |
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OH |
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O |
O |
H |
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+1.01 (296)146 |
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sh −1.3 (305), |
−1.55 (293), |
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||||
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|
−1.06 (247), |
+4.7 (212)147 |
||
194
RO
Stefan E. Boiadjiev and David A. Lightner
|
O |
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O |
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|
|
14β-H, R = H |
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−2.97 (313), |
−3.10 (304), |
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−0.39 (248), |
+2.2 (220) |
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|
R = Ac |
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H |
|
−4.11 (308), |
+2.3 (223) |
|
|
14α-H R = H sh +1.12(315), |
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H |
O |
+2.48(292), |
+4.2 (211) |
|
|
R = Ac |
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sh +1.16 (316), |
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H |
|
+2.80 (296), |
+3.7 (211)147 |
|
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O |
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O |
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O |
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H |
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O |
O |
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H |
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O H |
O |
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H |
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O |
||
OH |
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RO |
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O |
|
OH |
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O |
||
R = H −1.61 (294), sh −0.98 (257), |
+2.76 (294)148 |
|||
+5.9 (212) |
|
|
|
|
R = Ac −1.67 (293), sh −1.16 (257), |
|
|
|
|
+4.9 (212)147
O
O
HO
OAc
AcO
N
H
−3.91 (309), −1.29 (252)149 |
+4.57 (310)150 |