Chemistry Letters 2001
591
The representative procedure for the conversion of 2-bromo-
5-tosylpyrrole 10a to the corresponding 5-tosylpyrrolinone 13a
was as follows: To a solution of 89 mg (0.26 mmol) of 2-bromo-
3-ethyl-4-methyl-5-tosylpyrrole (10a) in 1 mL of TFA was added
0.74 ml of 0.705 M (= mol dm–3) TFA solution of DMSO (0.52
mmol) at room temperature under nitrogen atmosphere. After
stirring for 1 h, a catalytic amount (ca. 2 mg) of iodine and zinc
powder (34 mg, 0.52 mmol) were added and the mixture was
stirred for another 1 h at room temperature. After usual work-up,
3-ethyl-1,5-dihydro-4-methyl-5-tosyl-2H-pyrrol-2-one (13a) as
the D-ring of PCB (1) was isolated by preparative TLC [SiO2,
hexane/AcOEt (3/1, v/v)] in 94% yield (68 mg) (Entry 1 in Table
1). In a similar manner, other 5-tosylpyrrolinones 13b–i were
prepared from the corresponding 2-bromo-5-tosylpyrroles 10b–i
in good yields as summarized in Table 1. Thus, the present
method is much better than the previous one.4
In the case of 10f, it was necessary to use a large excess of
DMSO to get higher yield (Entry 6), probably due to the forma-
tion of the cyclic intermediate 14 in equilibrium with 15 and/or
16 in Scheme 2.
The 5-tosylpyrrolinoes 13a–i thus obtained were used to
synthesize various PCB derivatives 1–9 modified at the D-ring
in free acid forms with all-Z, all-syn conformations (confirmed
by NOESY) according to our previous method as shown in
Scheme 3.2 The resulting PCB derivatives 1–95 were employed
in assembly with phytochrome B apoprotein (PHYB) in vitro to
reveal the structural requirement of the side-chain of the D-ring
for the photoreversible spectral change of the adducts.3
The present work was financially supported in part by
Grant-in-Aid for Scientific Research from the Ministry of
Education, Science, Sports, and Culture.
References and Notes
1
W. Rüdiger and F. Thümmler, Angew. Chem., Int. Ed. Engl.,
30, 1216 (1991); M. Furuya and P.-S. Song, “Assembly and
Properties of Holophytochrome,” in “Photomorphogenesis in
Plants,” 2nd ed., ed. by R. E. Kendrick and G. H. M.
Kronenberg, Kluwer Academic Publishers, Dordrecht (1994),
Chap. 4.3, pp. 105–140; M. Stanek and K. Grubmayr, Chem.
Eur J. 4, 1653 and 1660 (1998). See also the references cited
therein.
2
a) K. Kohori, M. Hashimoto, H. Kinoshita, and K. Inomata,
Bull. Chem. Soc. Jpn., 67, 3088 (1994). b) T. Kakiuchi, H.
Kato, K. P. Jayasundera, T. Higashi, K. Watabe, D.
Sawamoto, H. Kinoshita, and K. Inomata, Chem. Lett., 1998,
1001. c) K. P. Jayasundera, H. Kinoshita, and K. Inomata,
Chem. Lett., 1998, 1227. d) T. Kakiuchi, H. Kinoshita, and K.
Inomata, Synlett, 1999, 901. e) K. P. Jayasundera, H.
Kinoshita, and K. Inomata, Bull. Chem. Soc. Jpn., 73, 497
(2000). f) A. Ohta, D. Sawamoto, K. P. Jayasundera, H.
Kinoshita, and K. Inomata, Chem. Lett., 2000, 492. g) D.
Sawamoto, H. Nakamura, H. Kinoshita, S. Fujinami, and K.
Inomata, Chem. Lett., 2000, 1398. See also the references
cited therein.
3
H. Hanzawa, K. Inomata, H. Kinoshita, T. Kakiuchi, K. P.
Jayasundera, D. Sawamoto, A. Ohta, K. Uchida, K. Wada, and
M. Furuya, Proc. Natl. Acad. Sci. U.S.A., 98, 3612 (2001).
Recently a related paper was reported: U. Robben, I. Lindner,
W. Gärtner, and K. Schaffner, Angew. Chem. Int. Ed., 40,
1048 (2001).
4
5
H. Kinoshita, Y. Hayashi, Y. Murata, and K. Inomata, Chem.
Lett., 1993, 1437.
Spectral data of the final products 1–9 are given for UV/Vis
(MeOH) λmax and HRMS (FAB) (M++1) in the following. 1:
see ref 2b. 2: 364 (40200), 621 (12600) nm; Calcd for
C34H41N4O6: m/z 601.3026. Found: 601.3026. 3: 364 (40600),
621 (13500) nm; Calcd for C36H45N4O6: m/z 629.3339. Found:
629.3340. 4: 364 (49800), 621 (16000) nm; Calcd for
C39H51N4O6: m/z 671.3808. Found: 671.3812. 5: 364 (45200),
621 (14200) nm; Calcd for C35H41N4O8: m/z 645.2924. Found:
645.2921. 6: 366 (61700), 621 (19100) nm; Calcd for
C
40H45N4O6S: m/z 709.3060. Found: 709.3063. 7: 364
(43800), 621 (14400) nm; Calcd for C34H41N4O6: m/z
601.3026. Found: 601.3023. 8: 364 (45100), 621 (14800) nm;
Calcd for C36H45N4O6: m/z 629.3339. Found: 629.3333. 9:
364 (54600), 621 (17300) nm; Calcd for C39H51N4O6: m/z
671.3808. Found: 671.3800.