Y. Araki et al. / Bioorg. Med. Chem. Lett. 16 (2006) 3302–3305
3305
4. Addicott, F. T., Ed. Abscisic Acid; Praeger: New York,
1983.
5. Kushiro, T.; Okamoto, M.; Nakabayashi, K.; Yamagishi,
K.; Kitamura, S.; Asami, T.; Hirai, N.; Koshiba, T.;
Kamiya, Y.; Nambara, E. ENBO J. 2004, 23, 1647.
6. Saito, S.; Hirai, N.; Matsumoto, C.; Ohigashi, H.; Ohta, D.;
Sakata, K.; Mizutani, M. Plant Physiol. 2004, 134, 1439.
7. Kitahata, N.; Saito, S.; Miyazawa, Y.; Umezawa, T.;
Shimada, Y.; Min, Y. K.; Mizutani, M.; Hirai, N.;
Shinozaki, K.; Yoshida, S.; Asami, T. Bioorg. Med. Chem.
2005, 13, 4491.
8. Correia, M. A.; Ortiz de Montellano, P. R. In Cytochrome
P450: Structure, Mechanism, and Biochemistry; Ortiz de
Montellano, P. R., Ed., third ed.; Kluwer Academic/
Plenum Publishers: New York, 2005; pp 247–322.
9. Ueno, K.; Yoneyama, H.; Saito, S.; Mizutani, M.; Sakata,
K.; Hirai, N.; Todoroki, Y. Bioorg. Med. Chem. Lett.
2005, 15, 5226, We named the lead compound in this ref.
as AHI1 in the present paper.
Figure 6. Enhanced effect of (+)-AHI4 on ABA activity in the rice
seedling elongation assay.9
10. Ueno, K.; Araki, Y.; Hirai, N.; Saito, S.; Mizutani, M.;
Sakata, K.; Todoroki, Y. Bioorg. Med. Chem. 2005, 13,
3359.
11. ( )-AHI4
[(2Z,4E)-5-((1S*,2S*,6S*)-1,2-dihydroxy-6-
methylcyclohexyl)penta-2,4-dienoic acid]: 1H NMR
(500 MHz, CDCl3): d 0.88 (3H, d, J = 7.0 Hz, H3-70), 1.21
(1H, m, H-30proS), 1.51 (1H, m, H-40), 1.62 (1H, m, H-
30proR), 1.68 (1H, m, H-40), 1.70 (1H, m, H-50proR), 1.83
(1H, m, H-50proS), 2.00 (1H, m, H-20), 3.73 (1H, dd, J = 5.2
and 2.7 Hz, H-60), 4.81 (2H, br, HO-10 and HO-60), 5.68
(1H, d, J = 11.3 Hz, H-2), 6.28 (1H, d, J = 15.3 Hz, H-5),
6.67 (1H, t, J = 11.3 Hz, H-3), 7.68 (1H, dd, J = 15.3 and
11.3 Hz, H-4); UV kmax (MeOH) nm (e): 257.2 (20,200);
HREIMS: [M]+ at m/z 226.1209 (C12H18O4 requires
27
226.1205). (+)-AHI4: ½aꢁD +32.5ꢁ (MeOH; c 0.0826). (ꢀ)-
27
AHI4: ½aꢁD ꢀ32.3ꢁ (MeOH; c 0.0867). An optical purity was
99% and 98% for (+)- and (ꢀ)-enantiomers (tR 11.8 and
9.5 min), respectively, on the basis of HPLC analysis
(Chiralpak AD-H 250 · 4.6 mm i.d., Daicel; mobile phase,
15% 2-PrOH in hexane containing 0.1% TFA; flow rate,
Figure 7. Drought tolerance of radish seedlings treated with (+)-
AHI4.17
1
1.0 mL minꢀ1; detection, 254 nm). H NMR data of (+)-
and (ꢀ)-AHI4 agreed with that of ( )-AHI4.
12. ( )-epi-AHI4 [(2Z,4E)-5-((1S*,2R*,6S*)-1,2-dihydroxy-6-
methylcyclohexyl)penta-2,4-dienoic acid]: 1H NMR
(500 MHz, CD3OD): d 0.84 (3H, d, J = 6.7 Hz, H3-70),
1.22 (1H, m, H-30proS), 1.44 (1H, m, H-40proR), 1.52 (2H,
m, H-30proR and H-50proS), 1.60 (1H, m, H-20), 1.76 (1H,
m, H-40proS), 1.82 (1H, m, H-50proR), 3.49 (1H, dd,
J = 11.3 and 4.6 Hz, H-60), 5.65 (1H, d, J = 11.0 Hz, H-2),
6.28 (1H, d, J = 14.6 Hz, H-5), 6.70 (1H, t, J = 11.0 Hz, H-
3), 7.64 (1H, dd, J = 14.6 and 11.0 Hz, H-4); UV kmax
(MeOH) nm (e): 256.8 (19,200); HREIMS: [M]+ at m/z
226.1211 (C12H18O4 requires 226.1205).
interaction relative to the CH–p interaction. The inhib-
itory activity of (+)-AHI4 is more than 10 times of that
of (+)-AHI1, equal to that of (+)-6-nor-ABA,10 and less
than one-tenth of that of uniconazole-P and (+)-dinico-
nazole.7 In light of the fact that (+)-AHI1 is 10 times less
effective than (+)-6-nor-ABA owing to the absence of
the ring enone, the present findings should aid in the
design of more effective, non-azole ABA 80-hydroxylase
inhibitors which are comparable to the azole-containing
class.
13. Gaussian 03, Revision C.02, Gaussian, Inc., Wallingford
CT, 2004.
14. Dale, J. A.; Mosher, H. S. J. Am. Chem. Soc. 1973, 95,
512.
Acknowledgment
15. Details in preparation and activity of optically pure AHI1
will be reported elsewhere.
16. Detailed procedures for the enzyme inhibition assay were
reported previously (see Ref. 10).
We thank Toray Industries Inc., Tokyo, Japan, for the
gift of (+)-ABA.
17. Seven-day-seedlings of radish [R. Sativus L. var. raphani-
stroides (Makino) Sinsk.] were prepared as reported
previously Todoroki, Y.; Sawada, M.; Matsumoto, M.;
Tsukada, S.; Ueno, K.; Isaka, M.; Owaki, M.; Hirai, N.
Bioorg. Med. Chem. 2004, 12, 363, Thirty-seven-day-
seedlings with roots were placed in a 400 lM (+)-AHI4 or
( )-epi-AHI4 solution for 1 day at 25 ꢁC in continuous
light and then transferred to a plastic tube with no
solution. Drought stress was by 9-h desiccation.
References and notes
1. Hirai, N. In Comprehensive Natural Products Chemistry;
Mori, K., Ed.; Elsevier: Amsterdam, 1999; Vol. 8, pp 72–91.
2. Davies, W. J.; Jones, H. G., Eds. Abscisic Acid; BIOS
Scientific Publishers: Oxford, 1991.
3. Zeevaart, J. A. D.; Creelman, R. A. Annu. Rev. Plant
Physiol. Plant Mol. Biol. 1998, 39, 439.