Total syntheses of (±)-crinine, (±)-crinamine, and (plusmn;)-6a-epi-crinamine via the regioselective synthesis and Diels-Alder reaction of 3-aryl-5-bromo-2-pyrone

Article abstract of DOI:10.1021/jo8008353

(Chemical Equation Presented) We have devised a new unified synthetic protocol to (±)-crinine, (±)-crinamine, and (±)-6a-epi- crinamine from the Diels-Alder cycloadduct of 3-(3,4-methylenedioxyphenyl)-5- bromo-2-pyrone with TBS vinyl ether. The requisite 3-(3,4-methylenedioxyphenyl)- 5-bromo-2-pyrone was prepared from the C3-selective Stille coupling reaction of 3,5-dibromo-2-pyrone. Also noted is that the vinyl bromide can be used as a handle for further derivatization.

Full text of DOI:10.1021/jo8008353

Total Syntheses of (()-Crinine, (()-Crinamine, and
(()-6a-epi-Crinamine via the Regioselective Synthesis and
Diels-Alder Reaction of 3-Aryl-5-bromo-2-pyrone
Nguyen Thanh Tam, Jayhyok Chang, Eun-Ju Jung, and Cheon-Gyu Cho*
Department of Chemistry, Hanyang UniVersity, Seoul, Korea 133-791
ccho@hanyang.ac.kr
ReceiVed April 19, 2008
We have devised a new unified synthetic protocol to (()-crinine, (()-crinamine, and (()-6a-epi-crinamine
from the Diels-Alder cycloadduct of 3-(3,4-methylenedioxyphenyl)-5-bromo-2-pyrone with TBS vinyl
ether. The requisite 3-(3,4-methylenedioxyphenyl)-5-bromo-2-pyrone was prepared from the C3-selective
Stille coupling reaction of 3,5-dibromo-2-pyrone. Also noted is that the vinyl bromide can be used as a
handle for further derivatization.
Introduction
physiological activities, as exemplified by the recent study
unveiling the highly selective apoptosis induction properties of
crinamine 2 and haemanthamine 3 against tumor cells at as low
as micromolar concentration.3
Belonging to the Amaryllidaceae natural product family, the
crinine-type alkaloids 1-31 (Figure 1) elicit continued interest
in the synthetic community2 due in part to their intriguing
Crinine alkaloids are closely related to other major Amaryl-
lidaceae family natural products, lycorane- and galanthamine-
type alkaloids, in the sense of biogenesis, being derived from
the same precursor norbelladine.4 As a part of our ongoing
research program on 3,5-dibromo-2-pyrone 4 and its derivatives
as novel enophile synthons,5 we have explored their potential
applicability to the target-oriented synthesis with the maximum
use of the resultant densely functionalized cycloadducts. Scheme
1 shows our previous efforts in this context, total syntheses of
(()-trans-dihydronarciclasine5b and (()-joubertinamine.5c The
(1) For a review on crinine type alkaloids, see: (a) Mori, M. Chem. Pharm.
Bull. 2005, 53, 457. (b) Jin, Z.; Li, Z.; Huang, R. Nat. Prod. Rep. 2002, 19, 454.
(c) Hoshino, O. In The Alkaloids; Brossi, A., Ed.; Academic Press: New York,
1998; Vol. 51, p 323. (d) Martin, S. F. In The Alkaloids; Brossi. A., Ed.;
Academic Press: New York, 1987; Vol. 30, p 251.
(2) For a synthesis of crinine and related alkaloids, see: (a) Bohno, M.; Sugie,
K.; Imase, H.; Yusof, Y. B.; Oishi, T.; Chida, N. Tetrahedron 2007, 63, 6977.
(b) Lebeuf, R.; Robert, F.; Schenk, K.; Landais, Y. Org. Lett. 2006, 8, 4755. (c)
Zhang, F.-M.; Tu, Y.-Q.; Liu, J.-D.; Fan, X.-H.; Shi, L.; Hu, X.-D.; Wang, S.-
H.; Zhang, Y.-Q. Tetrahedron 2006, 62, 9446. (d) Bru, C.; Guillou, C.
Tetrahedron 2006, 62, 9043. (e) Nishimata, T.; Sato, Y.; Mori, M. J. Org. Chem.
2004, 69, 1837. (f) Bohno, M.; Imase, H.; Chida, N. Chem. Commun. 2004,
1086. (g) Banwell, M. G.; Harvey, J. E.; Jolliffe, K. A. J. Chem. Soc., Perkin
Trans 1 2001, 17, 2002. (h) Baldwin, S. W.; Debenham, J. S. Org. Lett. 2000,
2, 99. (i) Watson, D. J.; Meyers, A. I. Tetrahedron Lett. 2000, 41, 1519. (j)
Rigby, J. H.; Cavezza, A.; Heeg, M. J. J. Am. Chem. Soc. 1998, 120, 3664. (k)
Pearson, W. H.; Lovering, F. E. J. Org. Chem. 1998, 63, 3607. (l) Pearson,
W. H.; Lovering, F. E. J. Am. Chem. Soc. 1995, 117, 12336. (m) Martin, S. F.;
Campbell, C. L. J. Org. Chem. 1988, 53, 3184. (n) Martin, S. F.; Campbell,
C. L. Tetrahedron Lett. 1987, 28, 503. (o) Overman, L. E.; Sugai, S. HelV. Chim.
Acta 1985, 68, 745. (p) Overman, L. E.; Mendelson, L. T.; Jacobsen, E. J. J. Am.
Chem. Soc. 1983, 105, 6629. (q) Sanchez, I. H.; Lopez, F. J.; Soria, J. J.; Larraza,
M. I.; Flores, H. J. J. Am. Chem. Soc. 1983, 105, 7640. (r) Danishefsky, S.;
Morris, J.; Mullen, G.; Gammill, R. J. Am. Chem. Soc. 1982, 104, 7591. (s)
Overman, L. E.; Mendelson, L. T. J. Am. Chem. Soc. 1981, 103, 5579. (t)
Sanchez, I. H.; Mendoza, M. T. Tetrahedron Lett. 1980, 21, 3651. (u) Isobe,
K.; Taga, J.; Tsuda, Y. Tetrahedron Lett. 1976, 2331. (v) Brossi, A.; Teitel, S.
J. Org. Chem. 1970, 35, 3559. (w) Whitlock, H. W., Jr.; Smith, G. L. J. Am.
Chem. Soc. 1967, 89, 3600. (x) Muxfeldt, H.; Schneider, R. S.; Mooberry, J. B.
J. Am. Chem. Soc. 1966, 88, 3670.
(3) McNulty, J.; Nair, J. J.; Codina, C.; Bastida, J.; Pandey, S.; Gerasimoff,
J.; Griffin, C. Phytochemistry 2007, 68, 1068.
(4) Jeffs, P. W.; Campbell, H. F.; Farrier, D. S.; Ganguli, G.; Martin, N. H.;
Molina, G. Phytochemistry. 1974, 13, 933.
6258 J. Org. Chem. 2008, 73, 6258–6264
10.1021/jo8008353 CCC: $40.75 2008 American Chemical Society
Published on Web 07/16/2008

Total Syntheses of Crinine-Type Alkaloids
yield (Scheme 3). Subsequent Diels-Alder cycloaddition reac-
tion with TBS vinyl ether 16 provided bicyclolactone 14 as a
mixture of endo/exo isomers (2:1, 71% combined yield). Again,
only moderate endo/exo diastereomeric selectivity was observed,
due to the steric bulk of the C3-aryl group (vide supra).
The endo-adduct 14a was then separated and carried through
the reaction sequence to facilitate the structural characterizations
(Scheme 4). Methanolysis of 14a gave alcohol 18 in 90% yield.
Protection of the resultant hydroxyl group as a MOM ether
followed by DIBAL reduction and mesylation afforded 19 in
good overall yield. As the Wittig olefination approach previously
employed in the joubertinamine synthesis5c turned out to be
unsatisfactory, a direct cyanation route was investigated.
Gratifyingly, when heated with NaCN in DMSO at 80 °C, the
neopentyl mesylate 19 afforded 20 in an unusually high yield
(72%).10 Reduction of the nitrile group with LiAlH4 followed
by Boc protection gave 21 in 71% overall yield. Removal of
the silyl group and oxidation of the resultant secondary alcohol
with the Dess-Martin periodinane (DMP) provided ketone 22
in 78% yield over two steps from 21.11 Subsequent treatment
with ZnBr2 in CH2Cl2 effected both Boc removal12 and
formation of the cyclic imine, which was then reduced with
LiAlH4 in ether to give 23 in 62% overall yield. The ring C in
24 was assembled upon heating with paraformaldehyde in the
presence of 6 N HCl at 50 °C, according to the procedure
reported by Pearson and co-workers.2k Reductive removal of
the vinyl bromide group followed by the inversion of the allylic
hydroxyl group through the known one-pot three-step process2k
furnished (()-crinine 1.
Synthesis of (()-6a-epi-Crinamine 2a and (()-Crinamine
2b. Further application of our strategy toward the synthesis of
(()-crinamine required stereoselective installation of hydroxyl
group on the R-C2 bridge of crinine. To this end, we have
prepared olefin 28 by following the four-step sequence com-
posed of methylation, reduction, oxidation, and the Wittig
reaction (Scheme 5). However, this sterically hindered terminal
olefin underwent little or no epoxidation reaction under the
conditions we employed. The dihydroxylation reaction with
OsO4 proceeded well in high yield, but with no diastereoselec-
tivity, providing 1:1 mixture of two diol products. We then
investigated the epoxidation reaction of aldehyde 27 (Table 1).
While the epoxidation with sulfonium ylide13 gave only
moderate selectivity and yield, the reaction with CH2I2/MeLi14
afforded two inseparable diastereomeric epoxides 29a and 29b
in good selectivity (∼6:1, 1H NMR ratio) and total yield (85%).
Upon epoxide opening with NaN3 and protection with MOM
group, the epoxide mixture 29 was converted into two diaster-
eomeric MOM ethers, 31a and 31b, which were readily
separated with column chromatography. We did not know the
relative stereochemistry of the major isomer 31a (to be as
shown) until the completion of the synthesis of 2a (vide infra).
FIGURE 1. Selected examples of crinine-type alkaloids.
Diels-Alder reaction of 4 with the highly functionalized styrene
5 provided bicyclolactone 6 in 98% yield with exclusive endo
selectivity (Scheme 1). Debrominations followed by acid-
catalyzed methanolysis afforded the key intermediate cyclo-
hexene 7 containing all necessary functional groups and correct
relative stereochemistry. A subsequent eight-step process includ-
ing a Curtius rearrangement and Bischler-Napielaski reaction
completed the first total synthesis of (()-trans-dihydronarci-
clasine. The synthesis of (()-joubertinamine required the
installation of 3,4-dimethoxyphenyl moiety at C3 position prior
to the cycloaddition. The Stille coupling reaction with aryltin 8
furnished the requisite 2-pyrone diene 9 in good yield and
regioselectivity. The cycloaddition with phenyl vinyl thioether
as an ethylene equivalent provided a mixture of endo/exo-
bicyclolactones 10 (2:1, 82% combined yield). Only moderate
endo/exo diastereomeric selectivity was observed, unlike the
parent 3,5-dibromo-2-pyrone, more similar to the cycloaddition
reactions of the analogous C3-substituted-2-pyrones.6 The steric
bulk is presumed to destabilize the endo-transition state at the
cycloaddition stage. The stereochemistry of the phenythio group
was not a concern in this case, as it needs to be removed later.
Thus, both isomers were carried through the sequence to furnish
(()-joubertinamine.
On the basis of these investigations, we have further envis-
aged the 2-pyrone-regioselective coupling-Diels-Alder strategy
could be effective in the synthesis of the crinine-type alkaloids.
Herein, we report the full account of our synthetic approach to
(()-crinine 1,7 (()-6a-epi-crinamine 2a, and (()-crinamine 2b.
Results and Discussion
Synthesis of (()-Crinine 1. Our synthetic program was
conceived by the retrosynthesis (Scheme 2) involving the
disconnections of both tetrahydroisoquinoline and pyrrolidine
rings to reveal the cyclohexene 13, which bears all functional
groups required for the synthesis of crinine. The final and key
elaboration called for bicyclolactone 14, the Diels-Alder adduct
of 2-pyrone 15 and TBS vinyl ether 16. The endo- and exo-
cycloadducts are tactically equivalent as the silyl ether group
would be oxidized to ketone (13 to 12).
The synthesis began with the C3-selective Stille coupling
reaction8 of 3,5-dibromo-2-pyrone 4 with aryltin 17,9 to give
3-(3,4-methylenedioxyphenyl)-5-bromo-2-pyrone 15 in 72%
(5) For a recent review and selected articles, see: (a) Kim, H.-Y.; Cho, C.-
G. Prog. Heterocycl. Chem. 2007, 18, 1. (b) Shin, I.-J.; Choi, E.-S.; Cho, C.-G.
Angew. Chem., Int. Ed. 2007, 46, 2303. (c) Tam, T.; Cho, C.-G. Org. Lett. 2007,
9, 3391. (d) Shin, J.-T.; Hong, S.-C.; Shin, S.; Cho, C.-G. Org. Lett. 2006, 8,
3339. (e) Ryu, K.; Cho, Y.-S.; Cho, C.-G. Org. Lett. 2006, 8, 3343. (f) Chung,
S.-I.; Seo, J.; Cho, C.-G. J. Org. Chem. 2006, 71, 6701. (g) Shin, J.-T.; Shin, S.;
Cho, C.-G. Tetrahedron Lett. 2004, 45, 5857. (h) Pang, S.-J.; Min, S.-H.; Lee,
H.; Cho, C.-G. J. Org. Chem. 2003, 68, 10191. For the preparation of 4, see: (i)
Cho, C.-G.; Kim, Y.-W.; Lim, Y.-K.; Park, J.-S.; Lee, H.; Koo, S. J. Org. Chem.
2002, 67, 290.
(9) Prepared from the commerically available 1-bromo-3,4-(methylenedioxy)
benzene via the Pd-catalyzed stannylation. Suginomo, H.; Orito, K.; Yorita, K.;
Ishikawa, M.; Shimoyama, N.; Sasaki, T. J. Org. Chem. 1995, 60, 3052.
(10) Varseev, G. N.; Maier, M. E. Org. Lett. 2007, 9, 1461.
(11) The isolated exo-adduct was subjected to the similar reaction sequence
to provide 23 in somewhat lower overall yield.
(12) Williams, R. M.; Cao, J.; Tsujishima, H. Angew. Chem., Int. Ed. 2000,
39, 2540.
(13) Nemoto, H.; Kurobe, H.; Fukumoto, K.; Kametani, T. J. Org. Chem.
1986, 51, 5311.
(6) Kim, W.-S.; Lee, J.-H.; Kang, J.; Cho, C.-G. Tetrahedron Lett. 2004,
45, 1683.
(14) Concellon, J. M.; Cuervo, H.; Fernandez-Fano, R. Tetrahedron 2001,
57, 8983.
(7) Portion of this work has been published in communication form: Tam,
N. T.; Cho, C.-G. Org. Lett. 2008, 10, 601.
(15) Likhitwitayawuid, K.; Angerhofer, C. K.; Chai, H.; Pezzuto, J. M.;
Cordell, G. A. J. Nat. Prod. 1993, 56, 1331.
(8) Kim, W. S.; Kim, H.-J.; Cho, C.-G. J. Am. Chem. Soc. 2003, 125, 14288.
J. Org. Chem. Vol. 73, No. 16, 2008 6259

Tam et al.
SCHEME 1. Syntheses of trans-Dihydronarciclasine and Joubertinamine
SCHEME 2. Retrosynthesis of (()-Crinine 1
SCHEME 3. Synthesis of Bicyclolactone 14
All attempts to epimerize the 6a-OH group of 2a were
fruitless (Scheme 6). Oxidation of the alcohol to ketone and
NaBH4 reduction provided 2:1 mixture of crinamine 2b and
6a-epi-crinamine 2a in total yield of 10%. These failures led
us to investigate the epimerization of the OH group before the
construction of tetrahydroisoquinoline ring (Table 2). While the
conversions based on displacement reaction (entries 1 and 2)16
were unsatisfactory, the oxidation followed by reduction ap-
proach was reasonably selective to afford 1:3 mixture of 36a
and 36b with good overall total yield (88%).
Upon protection as a MOM ether, the azide 31b was isolated
and subjected into the same reaction sequence employed for
(()-6a-epi-crinamine 2a (Scheme 4) to afford (()-crinamine
2b with similar overall yield (Scheme 7). Its 1H and 13C NMR
data matched the literature values of crinamine.15
The azide 31a was hydrolyzed to amine with PPh3/THF/H2O,
Boc protected, desilylated and oxidized to give ketone 33a. The
Boc removal and cyclic imine formation with ZnBr2, followed
by LiAlH4 reduction furnished 34a. Subsequent Pictet-Spengler
reaction constructed the tetrahydroisoquinoline ring of 35a.
The debromination reaction afforded 2a in good overall yield.
Direct comparison of its 1H and 13C NMR data with the
reported values of crinamine15 proved our end product 2a
the 6a-epimer of crinamine (Scheme 6).
In summary, we have devised a new unified synthetic protocol
to (()-crinine, (()-crinamine, and (()-6a-epi-crinamine via the
common intermediate 18 readily accessed from the Diels-Alder
(16) Moriarty, R. M.; Zhuang, H.; Penmasta, R.; Liu, K.; Awasthi, A. K.;
Tuladhar, S. M.; Rao, M. S. C.; Singh, V. K. Tetrahedron Lett. 1993, 34, 8029.
6260 J. Org. Chem. Vol. 73, No. 16, 2008

Total Syntheses of Crinine-Type Alkaloids
TABLE 1. Stereoselective Epoxidation of Aldehyde 27
SCHEME 4. Synthesis of (()-Crinine 1
entry
conditions
Me3S+I-, nBuLi, THF, 0 °C to rt, 1 h 40% (29a:29b ) 2:1)
CH2I2 MeLi, THF, 0 °C, 30 min 85% (29a:29b ) 6:1)
yield (1H NMR ratio)
1
2
SCHEME 6. Synthesis of 6a-epi-Crinamine 2a
SCHEME 5. Attempted Installation of Hydroxyl Group
Experimental Section
General Materials and Methods. See Supporting Information.
Synthesis of (()-Crinine 1. See Supporting Information.
Preparation of Methyl Ether 26. To a solution of 18 (700 mg,
1.44 mmol) in THF (14 mL) at 0 °C were added NaH (104 mg,
4.33 mmol) and MeI (0.45 mL, 7.21 mmol). After 2 h at room
temperature, the reaction mixture was quenched by adding MeOH
(1 mL), and the resulting solution was diluted with CH2Cl2 and
water. The organic layer was separated, dried over MgSO4,
concentrated, and purified by column chromatography (hexane/
EtOAc ) 9.5:0.5) to give 660 mg of 26 as a tan oil in 92% yield.
1H NMR (400 MHz, CDCl3) δ 6.75 (d, J ) 8.4 Hz, 1H), 6.71 (d,
J ) 1.6 Hz, 1H), 6.64 (dd, J ) 8.0, 1.6 Hz, 1H). 6.33 (s, 1H), 5.94
(d, J ) 1.2 Hz, 2H), 4.61 (d, J ) 6.0 Hz, 1H), 4.01 (t, J ) 6.0 Hz,
1H), 3.68 (s, 3H), 3.44 (s, 3H), 2.13-2.07 (m, 1H), 1.98-1.92
(m, 1H), 0.75 (s, 9H), -0.03 (s, 3H), -0.32 (s, 3H); 13C NMR
(100 MHz, CDCl3) δ 172.5, 147.5, 146.9, 132.1, 131.5, 126.7,
cycloaddition of 3-(3,4-methylenedioxyphenyl)-5-bromo-2-py-
rone with TBS vinyl ether. We are currently applying our
2-pyrone strategy toward total synthesis of other related
congeners, haemanthamine, precriwelline, and tazettine.
J. Org. Chem. Vol. 73, No. 16, 2008 6261

Tam et al.
C21H31BrNaO5Si [M + Na]+: 493.1016, found 493.1017. To a
solution of alcohol 26-a (380 mg, 0.81 mmol) and NaHCO3 (338
mg, 4.03 mmol) in CH2Cl2 (8 mL) was added the Dess-Martin
reagent (410 mg, 0.97 mmol). The reaction mixture was stirred at
room temperature for 30 min, and the resulting mixture was filtered
through a short pad of Celite, washed with ether. The filtrate was
concentrated and chromatographed (hexane/EtOAc ) 9.5:0.5) to
afford 360 mg of 27 as a colorless oil in 95% yield. 1H NMR (400
MHz, CDCl3) δ 9.49 (s, 1H), 6.81 (d, J ) 8.4 Hz, 1H), 6.71 (d, J
) 1.6 Hz, 1H), 6.61 (dd, J ) 8.4, 2.0 Hz, 1H), 6.21 (s, 1H), 5.97
(d, J ) 1.6 Hz, 2H), 4.57 (dd, J ) 7.6, 3.6 Hz, 1H), 3.99 (t, J )
5.2 Hz, 1H), 3.46 (s, 3H), 2.01-1.91 (m, 2H), 0.78 (s, 9H), 0.02
(s, 3H), -0.16 (s, 3H); 13C NMR (100 MHz, CDCl3) δ 196.0, 147.9,
147.5, 128.5, 128.3, 128.1, 123.1, 110.4, 108.1, 101.3, 77.9, 67.2,
64.5, 57.4, 34.1, 25.7, 17.9, -4.7, -5.2; FT-IR (CH2Cl2) 2957,
2924, 2857, 2817, 1720, 1487, 1242, 1124, 1083, 935, 831, 787,
675 cm-1; HRMS calcd for C21H29BrNaO5Si [M + Na]+: 491.0860,
found 491.0863.
TABLE 2. Stereochemical Inversion of the Hydroxyl Group of 36a
entry
conditions
yield
1
2
3
DEAD, p-NO2-PhCOOH, Ph3P, PhH, 50 °C no desired producta
(i) Tf2O/pyr/DCM; (ii) KNO2/18-C-6/DMF
65% (36a:36b ) 1:1)
88% (36a:36b ) 1:3)
(i) Dess-Martin; (ii) NaBH4
a Desired product: p-NO2-benzoate of 36b.
SCHEME 7. Synthesis of Crinamine 2b
Preparation of Epoxide 29 (29a:29b ) 6:1). To a solution of
27 (390 mg, 0.83 mmol) and diiodomethane (0.12 mL, 1.45 mmol)
in THF (8 mL) was added MeLi (1.3 mL, 1.6 M in ether) at 0 °C.
After 30 min, the mixture was treated with ice and extracted with
CH2Cl2. The organic extract was dried, filtered, concentrated, and
purified by column chromatography (hexane/EtOAc ) 9.5:0.5) to
give an inseparable mixture of 29a and 29b (340 mg, ratio ) 6:1,
85% total yield) as a tan oil. The following characterization of 29a
1
was made from the spectra of a 6:1 mixture of 29a and 29b. H
NMR (400 MHz, CDCl3) δ 6.96 (d, J ) 1.2 Hz, 1H), 6.81(dd, J )
8.4, 1.6 Hz, 1H), 6.74 (d, J ) 8.4 Hz, 1H), 5.94 (s, 2H), 5.91 (s,
1H), 4.26 (dd, J ) 10.8, 2.8 Hz, 1H), 3.88 (t, J ) 4.0 Hz, 1H),
3.45 (s, 3H), 3.46-3.43 (m, 1H), 2.73 (t, J ) 4.4 Hz, 1H),
2.55-2.53 (m, 1H), 2.04-1.99 (m, 1H), 1.85-1.78 (m, 1H), 0.87
(s, 9H), 0.08 (s, 3H), 0.03 (s, 3H); 13C NMR (100 MHz, CDCl3) δ
147.2, 146.6, 132.4, 132.3, 125.4, 122.4, 110.0, 107.5, 101.1, 79.2,
69.8, 57.3, 55.8, 51.5, 43.9, 33.6, 25.9, 18.0, -4.4, -5.0.
Preparation of Azide 31a. A sealed tube was charged with
epoxides 29 (272 mg, 0.563 mmol, 29a:29b ) 6:1), NaN3 (366
mg, 5.63 mmol), NH4Cl (300 mg), and MeOH (5 mL). After 36 h
at 50 °C, the reaction mixture was diluted with CH2Cl2, washed
with water, dried over MgSO4, concentrated, and purified by column
chromatography (hexane/EtOAc ) 9.5:0.5) to afford 226 mg of
the corresponding alcohols in 76% combined yield. To the solution
of the resultant azido alcohols in CH2Cl2 were added MOMCl (0.16
mL, 5 equiv) and DIPEA (0.37 mL, 5 equiv). After 6 h at 40 °C,
the reaction mixture was cooled to room temperature, diluted with
CH2Cl2, washed with water, and dried over MgSO4. After concen-
tration, the residue was purified by column chromatography
(hexane/EtOAc ) 9.5:0.5) to give 192 mg of 31a and 35 mg of
1
31b (92% total yield, both in colorless oil). 31a H NMR (400
MHz, CDCl3) δ 6.85 (s, 1H), 6.73 (s, 2H), 6.34 (s, 1H), 5.95 (s,
2H), 4.86 - 4.82 (m, 2H), 4.49 (dd, J ) 12.4, 2.4 Hz, 1H), 4.17
(dd, J ) 6.8, 2.4 Hz, 1H), 3.75 (d, J ) 3.2 Hz, 1H), 3.45 (s, 3H),
3.44 (s, 3H), 3.28-3.17 (m, 2H), 1.87 (d, J ) 13.6 Hz, 1H), 1.48
(td, J ) 8.8, 4.4 Hz, 1H), 0.88 (s, 9H), 0.16 (s, 3H), 0.08 (s, 3H);
13C NMR (100 MHz, CDCl3) δ 147.3, 146.8, 134.7, 131.0, 124.0,
123.3, 110.5, 107.4, 101.2, 98.7, 80.4, 80.2, 66.2, 57.7, 56.7, 56.4,
53.5, 33.5, 26.0, 18.2, -4.1, -4.3; FT-IR (CH2Cl2) 2928, 2892,
2856, 2112, 1505, 1487, 1361, 1241, 1145, 1097, 1037, 939, 743
cm-1; HRMS calcd for C24H36BrN3NaO6Si [M + Na]+: 592.1449,
found 592.1451.
Preparation of 32a. To a solution of 31a (300 mg, 0.53 mmol)
in THF (5 mL) and H2O (0.25 mL) was added PPh3 (207 mg, 0.79
mmol) at room temperature. After 2 h at 40 °C, the reaction solvent
was evaporated and the water was removed azeotropically with
benzene. After dilution in CH2Cl2 (5 mL), Et3N (0.1 mL) and Boc
anhydride (287 mg, 1.3 mmol) were added at 0 °C. The reaction
was stirred for 3 h at 0 °C, quenched with water and extracted
with CH2Cl2. The combined extract was dried over MgSO4,
concentrated, and purified by column chromatography (hexane/
121.3, 109.2, 107.7, 101.1, 76.9, 69.8, 60.1, 57.1, 52.7, 34.7, 25.7,
17.9, -4.9, -5.5; FT-IR (CH2Cl2) 2947, 2930, 2843, 2857, 1732,
1491, 1246, 1043, 832, 782, 740 cm-1; HRMS calcd for
C22H31BrNaO6Si [M + Na]+: 521.0965, found 521.0966.
Preparation of Aldehyde 27. To a flask charged with 26 (500
mg, 1 mmol) in THF (10 mL) was added LiAlH4 (57 mg, 1.5 mmol)
in THF (2 mL) at 0 °C. The reaction mixture was stirred for 15
min and quenched with 20% NaOH (aq), and the resulting solution
was extracted with CH2Cl2. The combined organic solution was
dried, filtered, concentrated, and chromatographed (hexane/EtOAc
) 9:1) to afford 432 mg of alcohol 26-a as a colorless oil in 92%
1
yield. H NMR (400 MHz, CDCl3) δ 6.91 (s, 1H), 6.77 (s, 2H),
6.35 (s, 1H), 5.95 (d, J ) 3.2 Hz, 2H), 4.12 (dd, J ) 12.0, 2.8 Hz,
1H), 4.04 (dd, J ) 11.2, 3.2 Hz, 1H), 3.83-3.81 (m, 1H), 3.75-3.69
(m, 1H), 3.47 (s, 3H), 1.86-1.82 (m, 1H), 1.67-1.60 (m, 1H),
1.28 (dd, J ) 9.6, 3.2 Hz, 1H), 0.88 (s, 9H), 0.12 (s, 3H), 0.07 (s,
3H); 13C NMR (100 MHz, CDCl3) δ 147.5, 146.8, 136.1, 130.6,
124.1, 123.2, 110.2, 107.6, 101.1, 80.6, 66.8, 66.6, 57.9, 54.9, 33.4,
25.9, 18.0, -4.4, -4.7; FT-IR (CH2Cl2) 3448, 2926, 2883, 2846,
1507, 1483, 1341, 1236, 927, 841, 675 cm-1; HRMS calcd for
6262 J. Org. Chem. Vol. 73, No. 16, 2008

Total Syntheses of Crinine-Type Alkaloids
EtOAc ) 9:1) to give 282 mg of 32a as a colorless oil in 84%
mixture was treated with 8 mL of 6 N HCl at room temperature.
The mixture was warmed to 50 °C and stirred for 15 h. After cooling
to room temperature, the reaction mixture was basified by the
addition of solid K2CO3 and then extracted with CH2Cl2 several
times. The combined organic solution was dried over MgSO4,
filtered, concentrated, and chromatoghraphed (CH2Cl2/MeOH ) 9.5:
0.5) to give 30 mg of 35a as a white solid in 72% yield. 1H NMR
(400 MHz, CDCl3) δ 6.83 (s, 2H), 6.55 (s, 1H), 5.95 (s, 2H),
4.62-4.59 (m, 1H), 4.43 (d, J ) 16.8 Hz, 1H), 4.01-3.97 (m,
1H), 3.82 (d, J ) 16.8 Hz, 1H), 3.80 (d, J ) 14.0 Hz, 1H), 3.48 (s,
3H), 3.35 (dd, J ) 13.6, 3.6 Hz, 1H), 2.52 (dd, J ) 14.0, 3.2 Hz,
1H), 2.36-2.30 (m, 1H), 1.90-1.81 (m, 1H); 13C NMR (100 MHz,
CDCl3) δ 147.2, 146.6, 131.4, 130.2, 127.3, 126.3, 107.2, 106.1,
101.3, 86.2, 77.7, 66.4, 62.6, 61.9, 57.1, 50.7, 31.6; FT-IR (CH2Cl2)
1
yield. H NMR (400 MHz, CDCl3) δ 6.86 (s, 1H), 6.72 (s, 2H),
6.22 (s, 1H), 5.94 (s, 2H), 5.34 (brs, 1H), 4.80-4.76 (m, 2H), 4.43
(d, J ) 11.6 Hz, 1H), 4.14-4.12 (m, 1H), 3.75 (d, J ) 3.6 Hz,
1H), 3.45 (s, 3H), 3.42 (s, 3H), 3.11-3.08 (m, 1H), 2.93-2.91
(m, 1H), 1.87 (d, J ) 13.2 Hz, 1H), 1.52-1.45 (m, 1H), 1.40 (s,
9H), 0.90 (s, 9H), 0.13 (s, 3H), 0.06 (s, 3H); 13C NMR (100 MHz,
CDCl3) δ 156.0, 147.2, 146.8, 134.6, 130.8, 124.0, 123.3, 110.5,
107.3, 101.0, 98.8, 82.0, 80.2, 79.0, 66.1, 57.8, 56.8, 56.0, 41.8,
33.2, 28.4, 26.0, 18.2, -3.5, -4.3; FT-IR (CH2Cl2) 3368, 2954,
2888, 1712, 1505, 1368, 1244, 1104, 834, 776 cm-1; HRMS calcd
for C29H46BrNNaO8Si [M + Na]+: 666.2068, found 666.2070.
Preparation of 33a. To a solution of 32a (390 mg, 0.61 mmol)
in CH2Cl2 (6 mL) was added Et3N (0.2 mL) and TBAF (1.2 mL,
1 M in THF) at 0 °C. After 4 h at 0 °C, the reaction mixture was
warmed to room temperature and partitioned into water and CH2Cl2.
The organic layer was separated, dried over MgSO4, filtered,
concentrated, and chromatographed (hexane/EtOAc/MeOH ) 70:
30:3) to give 302 mg of alcohol 32a-1 as a colorless oil in 94%
yield. 1H NMR (400 MHz, CDCl3) δ 6.90 (s, 1H), 6.80-6.76 (m,
2H), 6.22 (s, 1H), 5.97 (d, J ) 5.2 Hz, 2H), 5.13 (brs, 1H),
4.82-4.75 (m, 2H), 4.35 (t, J ) 9.6 Hz, 1H), 4.22 (d, J ) 6.8 Hz,
1H), 3.79 (d, J ) 3.6 Hz, 1H), 3.46 (s, 3H), 3.45 (s, 3H), 3.16
(ddd, J ) 13.6, 6.8, 2.4 Hz, 1H), 3.01-2.90 (m, 1H), 1.97-1.94
(m, 2H), 1.54 (td, J ) 12.8, 4.4 Hz, 1H), 1.41 (s, 9H); 13C NMR
(100 MHz, CDCl3) δ 155.9, 148.0, 147.1, 133.7, 130.3, 125.2,
122.6, 109.6, 108.2, 101.2, 98.9, 81.1, 80.2, 79.2, 64.7, 58.0, 56.2,
56.1, 41.7, 33.0, 28.4; FT-IR (CH2Cl2) 3388, 2969, 2931, 2903,
1695, 1505, 1490, 1238, 1025, 932, 816, 742 cm-1; HRMS calcd
for C23H32BrNNaO8 [M + Na]+: 552.1204, found 552.1205. To a
mixture of alcohol 32a-1 (200 mg, 0.38 mmol), NaHCO3 (158 mg,
1.89 mmol), and CH2Cl2 (4 mL) was added the Dess-Martin
reagent (192 mg, 0.45 mmol). After 30 min at room temperature,
the reaction mixture was filtered though a short pad of Celite and
washed with ether, and the resultant filtrate was concentrated and
chromatographed (hexane/EtOAc ) 9.5:0.5) to afford 180 mg of
3317, 3052, 2928, 2823, 1506, 1486, 1361, 1329, 1108, 1036 cm-1
;
HRMS calcd for C17H18BrNNaO4 [M + Na]+: 402.0311, found
402.0312.
Preparation of 2a. A sealed tube was charged with 35a (30
mg, 0.08 mmol), benzene (1.5 mL), AIBN (13 mg, 0.08 mmol),
and tributyltin hydride (0.1 mL). After 2 h at 80 °C, the reaction
mixture was cooled to room temperature and partitioned into CH2Cl2
and aqueous KF solution. The organic solution was separated, dried
over MgSO4, filtered, concentrated, and purified by silica gel
chromatography (CH2Cl2/MeOH ) 9.5:0.5 to 9:1) to give 18 mg
of (()-6a-epi-crinamine 2a as a while solid in 75% yield. 1H NMR
(400 MHz, CDCl3) δ 6.85 (s, 1H), 6.56 (s, 1H), 6.40 (dd, J )
10.4, 2.0 Hz, 1H), 5.95 (d, J ) 2.0 Hz, 2H), 5.91 (d, J ) 10.4 Hz,
1H), 4.55 (brs, 1H), 4.49 (d, J ) 17.2 Hz, 1H), 4.00-3.96 (m,
1H), 3.87 (d, J ) 17.2 Hz, 1H), 3.86-3.82 (m, 1H), 3.42 (s, 3H),
3.35 (d, J ) 12.4 Hz, 1H), 2.56 (d, J ) 14.0 Hz, 1H), 2.27-2.21
(m, 1H), 1.64 (q, J ) 12.0 Hz, 1H); 13C NMR (100 MHz, CDCl3)
δ 147.2, 146.8, 131.0, 130.2, 127.5, 125.7, 107.2, 106.3, 101.3,
86.3, 75.9, 67.0, 62.4, 61.9, 56.2, 48.5, 30.6; HRMS calcd for
C17H19NNaO4 [M + Na]+: 324.1206, found 324.1207.
Preparation of 36 (36a:36b ) 1:3). To a mixture of 260 mg
(0.494 mmol) of 36 (36a:36b ) 6:1, prepared from 29, Scheme
6), NaHCO3 (207 mg, 2.47 mmol), and CH2Cl2 (5 mL) was added
the Dess-Martin reagent (250 mg, 0.593 mmol). After 30 min at
room temperature, the reaction mixture was filtered though a short
pad of Celite and washed with ether, and the filtrate was
concentrated and chromatographed (hexane/EtOAc ) 9.5:0.5) to
1
33a as a colorless oil in 90% yield. H NMR (400 MHz, CDCl3)
δ 6.77-6.72 (m, 3H), 6.57 (s, 1H), 5.97 (d, J ) 4.4 Hz, 2H), 5.43
(brs, 1H), 4.79 (d, J ) 6.8 Hz, 1H), 4.59-4.54 (m, 2H), 4.29 (d,
J ) 3.2 Hz, 1H), 3.41 (s, 3H), 3.39 (s, 3H), 2.99-2.90 (m, 2H),
2.75 (d, J ) 14.4, 5.2 Hz, 1H), 2.61-2.57 (m 1H), 1.40 (s, 9H);
13C NMR (100 MHz, CDCl3) δ 203.9, 156.0, 148.6, 147.7, 132.8,
129.8, 123.8, 120.5, 108.8, 107.1, 101.5, 98.7, 81.0, 80.8, 79.0,
63.0, 56.5, 56.0, 42.4, 40.9, 28.4; FT-IR (CH2Cl2) 3366, 2970, 2889,
1714, 1695, 1513, 1487, 1368, 1236, 1161, 1035, 934 cm-1; HRMS
calcd for C23H30BrNaNO8 [M + Na]+: 550.1047, found 550.1049.
Preparation of 34a. A mixture of 33a (45 mg, 0.085 mmol),
excess ZnBr2 (5 equiv), and CH2Cl2 (2 mL) was stirred at room
temperature for 5 h. The reaction mixture was then diluted with
ether (0.5 mL) and cannulated to a suspension of LiAlH4 (32 mg,
0.85 mmol) in ether (1 mL) at -10 °C. After 15 min, the reaction
mixture was quenched with aqueous 20% NaOH and extracted with
CH2Cl2 several times. The combined organic solution was dried
over MgSO4, filtered, concentrated, and chromatographed (CH2Cl2/
MeOH ) 9.8:0.2 to 9.5:0.5) to afford 17 mg of 34a as a tan oil in
1
afford 240 mg of ketone 36-a as a colorless oil in 93% yield. H
NMR (400 MHz, CDCl3) δ 6.79 (d, J ) 8.0 Hz, 1H), 6.66 (d, J )
1.2 Hz, 1H), 6.58 (dd, J ) 8.0, 1.2 Hz, 1H), 6.31 (s, 1H), 5.96 (d,
J ) 3.2 Hz, 2H), 4.63 (d, J ) 5.6 Hz, 1H), 4.06-4.02 (m, 1H),
3.94 (d, J ) 17.6 Hz, 1H), 3.77 (d, J ) 17.6 Hz, 1H), 3.43 (s, 3H),
2.27-2.21 (m, 1H), 1.96-1.90 (m, 1H), 0.72 (s, 9H), -0.04 (s,
3H), -0.44 (s, 3H); 13C NMR (100 MHz, CDCl3) δ 201.7, 148.3,
147.5, 130.7, 130.5, 128.2, 121.1, 108.7, 108.5, 101.4, 76.2, 70.3,
64.3, 57.1, 54.8, 34.9, 25.7, 17.8, -4.9, -5.7; FT-IR (CH2Cl2) 2948,
2929, 2858, 2108, 1722, 1504, 1489, 1249, 1095, 964, 941, 836
cm-1; HRMS calcd for C22H30BrN3NaO5Si (M+1)+: 546.1030,
found 546.1032. To a solution of ketone 36-a (225 mg, 0.43 mmol)
in MeOH (4 mL) was added 65 mg (1.72 mmol) of NaBH4 in
MeOH (1 mL) at 0 °C. After 15 min, the reaction mixture was
quenched with H2O and extracted with CH2Cl2. The combined
extract was dried over MgSO4, concentrated and chromatographed
(hexane/EtOAc ) 9.5:0.5) to afford a mixture of 36a and 36b (215
mg, ratio ) 1:3, 95% combined yield) as a colorless oil. Spectral
1
48% yield. H NMR (400 MHz, CDCl3) δ 6.87 (s, 1H), 6.76 (s,
2H), 6.32 (s, 1H), 5.95 (s, 2H), 4.35 (d, J ) 6.8 Hz, 1H), 4.19 (d,
J ) 6.8 Hz, 1H), 4.06 (t, J ) 4.8 Hz, 1H), 3.72 (brs, 1H), 3.69 (d,
J ) 3.6 Hz, 1H), 3.49 (s, 3H), 3.45 (dd, J ) 12.8, 6.0 Hz, 1H),
3.06 (s, 3H), 2.95 (dd, J ) 12.4, 3.6 Hz, 1H), 2.44 (d, J ) 15.2
Hz, 1H), 1.79 (dt, J ) 15.2, 3.6 Hz, 1H); 13C NMR (100 MHz,
CDCl3) δ 147.4, 146.2, 135.3, 133.5, 122.9, 121.4, 109.1, 107.8,
101.1, 95.6, 84.6, 77.6, 60.5, 58.4, 57.3, 55.6, 52.7, 26.4; FT-IR
(CH2Cl2) 3355, 2928, 2888, 2816, 1735, 1499, 1435, 1236, 1144,
941, 737 cm-1; HRMS calcd for C18H22BrNNaO5 [M + Na]+:
434.0574, found 434.0575.
1
data of 36b were deduced from the mixture. H NMR (400 MHz,
CDCl3) δ 6.98 (d, J ) 1.6 Hz, 1H), 6.83-6.77 (m, 2H), 6.34 (s,
1H), 5.98-5.97 (m, 2H), 4.46-4.43 (m, 1H), 4.12 (dd, J ) 11.6,
2.8 Hz, 1H), 3.77-3.76 (m, 1H), 3.45 (s, 3H), 3.40-3.31 (m, 2H),
1.83-1.79 (m, 1H), 1.58-1.49 (m, 1H), 0.90 (s, 9H), 0.13 (s, 3H),
0.07 (s, 3H); 13C NMR (100 MHz, CDCl3) δ 147.8, 147.0, 133.2,
130.4, 124.6, 123.5, 110.2, 107.8, 101.3, 80.5, 73.2, 66.6, 58.1,
56.8 53.1, 33.7, 25.8, 18.0, -4.1, -4.6.
Preparation of 35a. To a solution of 34a (45 mg, 0.11 mmol)
in MeOH (0.8 mL) was added 1.0 mL of 37% aqueous solution of
formaldehyde at room temperature. After 10 min, the reaction
Preparation of 31b. A solution of 400 mg (0.76 mmol) of 36a
and 36b (1:3), MOMCl (0.29 mL, 3.8 mmol), and DIPEA (0.65
J. Org. Chem. Vol. 73, No. 16, 2008 6263

Tam et al.
mL, 3.8 mmol) was heated at 40 °C for 6 h. After cooling to room
temperature, the reaction mixture was diluted with CH2Cl2, washed
with water, dried over MgSO4, concentrated, and purified by column
chromatography (hexane/EtOAc ) 9.5:0.5) to give 295 mg of 31b
and 108 mg of 31a (93% total yield, both as a colorless oil). 31b
1H NMR (400 MHz, CDCl3) δ 7.07 (d, J ) 0.8 Hz, 1H), 6.88 (d,
J ) 9.2 Hz, 1H), 6.74-6.72 (m, 1H), 6.50 (s, 1H), 5.94 (d, J )
3.2 Hz, 2H), 4.49 (d, J ) 6.8 Hz, 1H), 4.35 (d, J ) 6.8 Hz, 1H),
4.23-4.17 (m, 2H), 3.76-3.74 (m, 1H), 3.58 (dd, J ) 13.2, 2.8
Hz, 1H), 3.44 (s, 3H), 3.38 (dd, J ) 12.8, 7.2 Hz, 1H), 3.06 (s,
3H), 1.88-1.84 (m, 1H), 1.64-1.58 (m, 1H), 0.90 (s, 9H), 0.10
(s, 3H), 0.08 (s, 3H); 13C NMR (100 MHz, CDCl3) δ 147.1, 146.5,
134.8, 132.8, 124.4, 123.4, 110.5, 107.2, 101.0, 97.6, 80.1, 79.8,
67.9, 57.9, 56.3, 56.0, 53.3, 33.7, 25.9, 18.1,-3.9, -4.5; FT-IR
(CH2Cl2) 2949, 2925, 2885, 2853, 2104, 1506, 1482, 1101, 1034,
935, 836, 776 cm-1; HRMS calcd for C24H36BrN3NaO6Si [M +
Na]+: 592.1449, found 592.1450.
Preparation of 32b. A mixture of 290 mg (0.51 mmol) of 31b
in THF (5 mL), H2O (0.3 mL) and 202 mg (0.76 mmol) of PPh3
was heated at 40 °C for 2 h. The solvent was evaporated, and the
water was removed azeotropically with benzene. The crude amine
product was dissolved in 5 mL of CH2Cl2 and added to 0.17 mL
of Et3N and 278 mg (1.27 mmol) of Boc anhydride at 0 °C. The
reaction was stirred for 3 h at 0 °C, quenched with water, and
extracted with CH2Cl2. The combined extract was dried over
MgSO4, concentrated, and purified by column chromatography
(hexane/EtOAc ) 9:1) to give 283 mg of 32b as a colorless oil in
86% yield. 1H NMR (400 MHz, CDCl3) δ 7.04 (s, 1H), 6.84 (d, J
) 8.0 Hz, 1H), 6.71 (d, J ) 8.0 Hz, 1H), 6.44 (s, 1H), 5.94 (d, J
) 2.4 Hz, 2H), 5.34 (brs, 1H), 4.13-4.27 (m, 2H), 4.22 (d, J )
6.8 Hz, 1H), 4.05 (d, J ) 6.8 Hz, 1H), 3.74 (d, J ) 2.8 Hz, 1H),
3.65 (dd, J ) 12.8, 7.2 Hz, 1H), 3.42 (s, 3H), 3.02 (s, 3H),
3.08-3.04 (m, 1H), 1.82 (d, J ) 13.6 Hz, 1H), 1.59-1.51 (m,
1H), 1.44 (s, 9H), 0.89 (s, 9H), 0.15 (s, 3H), 0.10 (s, 3H); 13C
NMR (100 MHz, CDCl3) δ 155.8, 147.0, 146.4, 134.6, 133.2, 124.3,
123.4, 110.5, 107.1, 101.0, 98.1, 83.0, 80.0, 79.0, 67.7, 57.6, 56.5,
55.9, 41.9, 33.9, 28.5, 25.9, 18.1, -4.1, -4.7; FT-IR (CH2Cl2) 3364,
2954, 2934, 2890, 1713, 1503, 1483, 1240, 1173, 1041, 938, 843
cm-1; HRMS calcd for C29H46BrNNaO8Si [M + Na]+: 666.2068,
found 666.2068.
2.72-2.61 (m, 2H), 1.45 (s, 9H); 13C NMR (100 MHz, CDCl3) δ
203.4, 155.8, 148.2, 147.4, 133.3, 131.4, 122.8, 120.9, 108.3, 107.8,
101.4, 97.3, 81.9, 80.4, 79.0, 62.2, 57.8, 55.8, 42.5, 42.2, 28.6;
FT-IR (CH2Cl2) 3359, 2978, 2932, 2891, 1714, 1502, 1249, 1162,
1038, 926, 744 cm-1; HRMS calcd for C23H30BrNaNO8 [M + Na]+:
550.1047, found 550.1050.
Preparation of 34b. A mixture of 33b (40 mg, 0.076 mmol),
excess ZnBr2 (5 equiv), and CH2Cl2 (1.5 mL) was stirred at room
temperature for 5 h. This mixture was diluted with ether (0.5 mL)
and cannulated into a suspension of LiAlH4 (0.29 mg, 0.76 mmol)
in ether (1 mL) at -10 °C. After 15 min, the reaction mixture was
quenched with aqueous 20% NaOH and extracted with CH2Cl2.
The combined organic solution was dried over MgSO4, filtered,
concentrated, and chromatographed (CH2Cl2/MeOH ) 9.5:0.5 to
9.0:1.0) to afford 16 mg of 34b as a tan oil in 51% yield. 1H NMR
(400 MHz, CDCl3) δ 6.83 (d, J ) 0.8 Hz, 1H), 6.78-6.73 (m,
2H), 6.52 (s, 1H), 5.95 (s, 2H), 4.64 (t, J ) 7.6 Hz, 1H), 4.52 (d,
J ) 6.4 Hz, 1H), 4.47 (d, J ) 6.4 Hz, 1H), 3.75 (d, J ) 4.4 Hz,
1H), 3.50 (s, 3H), 3.40 (brs, 1H), 3.32-3.23 (m, 1H), 3.18 (s, 3H),
3.00-2.93 (m, 1H), 2.26 (dd, J ) 15.2, 2.4 Hz, 1H), 1.71-1.65
(m, 1H); 13C NMR (100 MHz, CDCl3) δ 148.1, 146.5, 135.2, 131.8,
123.6, 120.2, 108.3, 107.1, 101.2, 96.2, 85.0, 78.0, 61.5, 58.5, 56.3,
55.5, 50.3, 26.6; FT-IR (CH2Cl2) 3363, 2931, 2882, 1502, 1490,
1437, 1240, 1086, 1050, 941, 808, 739 cm-1; HRMS calcd for
C18H22BrNNaO5 [M + Na]+: 434.0574, found 434.0572.
Preparation of 35b. To a solution of 34b (40 mg, 0.097 mmol)
in MeOH (0.8 mL) was added 1.0 mL of 37% aqueous solution of
formaldehyde. After 10 min, to this solution was added with 8.5
mL of 6N HCl at room temperature. After 15 h at 50 °C, the
reaction mixture was cooled to room temperature, basified by adding
solid K2CO3 and then extracted with CH2Cl2. The combined organic
solution was dried over MgSO4, filtered, concentrated, and chro-
matoghraphed to give 28 mg of 35b as a while solid in 76% yield.
1H NMR (400 MHz, CDCl3) δ 6.79 (s, 1H), 6.72 (s, 1H), 6.48 (s,
1H), 5.91 (s, 2H), 4.30 (d, J ) 16.8 Hz, 1H), 4.08-3.98 (m, 2H),
3.68 (d, J ) 16.8 Hz, 1H), 3.45 (s, 3H), 3.43-3.32 (m, 2H),
3.30-3.26 (m, 1H), 2.44-2.35 (m, 1H), 2.20-2.15 (m, 1H); 13C
NMR (100 MHz, CDCl3) δ 146.8, 146.6, 134.0, 131.7, 127.8, 126.5,
107.1, 103.2, 101.1, 80.2, 77.8, 66.0, 63.4, 61.2, 56.1, 52.9, 30.8;
HRMS calcd for C17H18BrNNaO4 [M + Na]+: 402.0311, found
402.0308.
Preparation of 33b. To a solution of 32b (168 mg, 0.261 mmol)
in CH2Cl2 (2.5 mL) was added Et3N (0.1 mL) and TBAF (0.5 mL,
1 M in THF) at 0 °C. The reaction was stirred for 4 h at 0 °C.
After warming to room temperature, the reaction mixture was
treated with water and extracted with CH2Cl2. The organic layer
was separated, dried over MgSO4, filtered, concentrated, and
chromatographed (hexane/EtOAc/MeOH ) 70:30:3) to give 133
mg of alcohol 32b-1 as a colorless oil in 96% yield. 1H NMR (400
MHz, CDCl3) δ 7.03 (s, 1H), 6.82 (d, J ) 8.0 Hz, 1H), 6.76 (d, J
) 8.0 Hz, 1H), 6.34 (s, 1H), 5.95 (d, J ) 4.8 Hz, 2H), 5.30 (brs,
1H), 4.62-4.53 (m, 2H), 4.34 (d, J ) 10.8 Hz, 1H), 4.01 (d, J )
4.8 Hz, 1H), 3.81 (s, 1H), 3.64-3.51 (m, 1H), 3.46 (s, 3H), 3.30
(s, 3H), 2.95-2.91 (m, 2H), 1.93 (d, J ) 13.6 Hz, 1H), 1.63-1.56
(m, 1H), 1.44 (s, 9H); 13C NMR (100 MHz, CDCl3) δ 156.2, 147.5,
146.7, 133.9, 131.3, 125.2, 123.1, 110.2, 107.6, 101.1, 98.2, 85.1,
80.0, 79.6, 67.1, 58.0, 56.1, 56.0, 43.0, 32.7, 28.4; FT-IR (CH2Cl2)
3389, 2978, 2932, 2891, 1714, 1502, 1249, 1162, 1038, 926, 744
cm-1; HRMS calcd for C23H32BrNNaO8 [M + Na]+: 552.1204,
found 552.1205. To a mixture of alcohol 32b-1 (133 mg, 0.251
mmol), NaHCO3 (105 mg, 1.25 mmol), and CH2Cl2 (2.5 mL) was
added the Dess-Martin reagent (128 mg, 0.3 mmol). After 30 min
at room temperature, the reaction mixture was filtered through a
short pad of Celite and washed with ether. The filtrate was
concentrated and chromatographed (hexane/EtOAc ) 8:2) to afford
120 mg of 33b as a colorless oil in 91% yield. 1H NMR (400 MHz,
CDCl3) δ 6.90 (s, 1H), 6.83 (dd, J ) 8.0, 1.2 Hz, 1H), 6.75 (d, J
) 8.0 Hz, 1H), 6.69 (s, 1H), 5.95 (s, 2H), 5.39 (brs, 1H), 4.55 (t,
J ) 5.6 Hz, 1H), 4.36 (d, J ) 6.8 Hz, 1H), 4.20-4.17 (m, 2H),
3.49 (s, 3H), 3.34-3.24 (m, 1H), 3.13-3.07 (m, 1H), 3.05 (s, 3H),
Preparation of 2b. A sealed tube was charged with 35b (24
mg, 0.06 mmol), benzene (1.2 mL), AIBN (10 mg, 0.06 mmol),
and tributyltin hydride (0.1 mL). After 2 h at 80 °C, the reaction
mixture was cooled to room temperature, and partitioned into
CH2Cl2 and aqueous KF solution. The organic layer was separated,
dried over MgSO4, filtered, concentrated, and purified by silica gel
chromatography (CH2Cl2/MeOH ) 9.5:0.5 to 9.0:1.0) to give 14
1
mg of (()-crinamine 2b as a while solid in 74% yield. H NMR
(400 MHz, CDCl3) δ 6.80 (s, 1H), 6.48 (s, 1H), 6.26 (s, 2H), 5.90
(d, J ) 2.0 Hz, 2H), 4.33 (d, J ) 17.0 Hz, 1H), 4.02 (dd, J ) 10.4,
6.0 Hz, 1H), 3.98-3.96 (m, 1H), 3.71 (d, J ) 17.0 Hz, 1H), 3.41
(s, 3H), 3.39-3.32 (m, 2H), 3.23 (dd, J ) 13.2, 4.4 Hz, 1H),
2.17-2.07 (m, 2H); 13C NMR (100 MHz, CDCl3) δ 146.6, 146.3,
136.2, 135.5, 126.7, 123.7, 106.9, 103.3, 100.9, 80.1, 76.1, 66.3,
63.6, 61.3, 55.9, 50.4, 30.3. The spectral data matched the literature
values of crinamine.16
Acknowledgment. Financial support was provided by a grant
from the Korea Research Foundation (KRF-2007-314-C00164).
N.T.T., C.J., and J.E.J. thank the BK21 and Seoul Fellowship.
Supporting Information Available: Experimental details for
1
the synthesis of (()-crinine 1 and copies of H and 13C NMR
spectra of synthetic intermediates en route to the final products
(()-6a-epi-crinamine 2a and (()-crinamine 2b. This material
is available free of charge via the Internet at http://pubs.acs.org.
JO8008353
6264 J. Org. Chem. Vol. 73, No. 16, 2008