Chemoenzymatic synthesis of amaryllidaceae constituents and biological evaluation of their C-1 analogues. the next generation synthesis of 7-deoxypancratistatin and trans -dihydrolycoricidine

Article abstract of DOI:10.1021/jo1003136

An efficient synthesis of C-1 derivatives of 7-deoxypancratistatin is reported. The key steps include the following: selective opening of an epoxide with aluminum acetylide in the presence of an aziridine; solid-state silica-gel-catalyzed opening of an aziridine; and oxidative cleavage of a phenanthrene core and its recyclization to phenanthridone to provide the key C-1 aldehyde 22. The conversion of this aldehyde to C-1 acetoxymethyl and C-1 hydroxymethyl derivatives is described along with the evaluation of their biological activity against several cancer cell lines and in an apoptosis study. The C-1 acetoxymethyl derivative has shown promising activity comparable to that of the natural product. In addition, a total synthesis of trans-dihydrolycoricidine and a formal total synthesis of 7-deoxypancratistatin are reported from aldehyde 22. Detailed experimental and spectral data are provided for all new compounds.

Full text of DOI:10.1021/jo1003136

pubs.acs.org/joc
Chemoenzymatic Synthesis of Amaryllidaceae Constituents and
Biological Evaluation of their C-1 Analogues. The Next Generation
Synthesis of 7-Deoxypancratistatin and trans-Dihydrolycoricidine†
Jonathan Collins, Uwe Rinner, Michael Moser, and Tomas Hudlicky*
Chemistry Department and Centre for Biotechnology, Brock University, 500 Glenridge Avenue,
St. Catharines, Ontario L2S 3A1, Canada
Ion Ghiviriga
Chemistry Department, University of Florida, Gainesville, Florida 32611
Anntherese E. Romero and Alexander Kornienko
Chemistry Department, New Mexico Institute of Mining and Technology, 801 Leroy Place, Socorro,
New Mexico 87801
Dennis Ma, Carly Griffin, and Siyaram Pandey
Department of Chemistry and Biochemistry, University of Windsor, 401 Sunset Avenue, Windsor,
Ontario N9B 3P4, Canada
thudlicky@brocku.ca
Received February 22, 2010
An efficient synthesis of C-1 derivatives of 7-deoxypancratistatin is reported. The key steps include
the following: selective opening of an epoxide with aluminum acetylide in the presence of an aziridine;
solid-state silica-gel-catalyzed opening of an aziridine; and oxidative cleavage of a phenanthrene core
and its recyclization to phenanthridone to provide the key C-1 aldehyde 22. The conversion of this
aldehyde to C-1 acetoxymethyl and C-1 hydroxymethyl derivatives is described along with the
evaluation of their biological activity against several cancer cell lines and in an apoptosis study. The
C-1 acetoxymethyl derivative has shown promising activity comparable to that of the natural
product. In addition, a total synthesis of trans-dihydrolycoricidine and a formal total synthesis of
7-deoxypancratistatin are reported from aldehyde 22. Detailed experimental and spectral data are
provided for all new compounds.
Introduction
family had been known for centuries, but only in the past few
decades were the active cytotoxic principles isolated and sub-
jected to medicinal evaluation as promising antitumor agents.
From such studies pancratistatin (2) and narciclasine (4),
More than 100 constituents have been isolated from various
Amaryllidaceae species since the identification of lycorine (1) in
1877.2 The medicinal value of the plants of the Amaryllidaceae
(1) Collins, J.; Drouin, M.; Sun, X.; Rinner, U.; Hudlicky, T. Org. Lett.
2008, 10, 361.
(2) Gerrard, A. W. Pharm. J. 1877, 8, 214.
† For a preliminary account see ref 1.
DOI: 10.1021/jo1003136
r
Published on Web 04/07/2010
J. Org. Chem. 2010, 75, 3069–3084 3069
2010 American Chemical Society

Collins et al.
JOCArticle
The synthetic community took active notice of these
constituents starting in the 1970s with the first synthesis of
lycoricidine4 by Ohta in 1975. The total syntheses of the
constituents followed: lycorine5 in 1975 by Tsuda, 7-deoxy-
pancratistatin6 in 1976 by Ohta, trans-dihydrolycoricidine7
in 1978 by Isobe, pancratistatin8 in 1989 by Danishefsky,
narciclasine9 in 1997 by Rigby, and trans-dihydronarcicla-
sine10 in 2007 by Cho.
The activity in total synthesis has not diminished as
evidenced by the number of creative approaches that con-
tinue to appear in the literature as well as the number of
reviews published on the topic of total synthesis and bio-
logy.11 Our research program in this area started with the
chemoenzymatic total synthesis of lycoricidine in 1992 and
continued with the first asymmetric synthesis of pancratis-
tatin in 1995. Since that time we have focused our program
on two major goals, the first being the provision of practical
and scaleable synthesis of pancratistatin or narciclasine in
order to solve the supply problem of these compounds. The
second goal, pursued in collaboration with Pettit’s group,
FIGURE 1. Representative members of the Amaryllidaceae con-
stituents.
Figure 1, emerged as the most active compounds, with the
corresponding 7-deoxy congeners, 7-deoxypancratistatin (3)
and lycoricidine (4), less active.3 The drop in activity was attri-
buted to be the consequence of the missing donor-acceptor
quality of the phenanthridone-phenol functionality in the latter
group of compounds. The saturated constituents 6 and 7 lack
C-1 functionality and are also less active.
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Heterocycles 1978, 9, 625. (b) Chida, N.; Jitsuoka, M.; Yamamoto, Y.;
Ohtsuka, M.; Ogawa, S. Heterocycles 1996, 43, 1385. (c) Fujimura, T.;
Shibuya, M.; Ogasawara, K.; Iwabuchi, Y. Heterocycles 2005, 66, 167.
(d) Szanto, G.; Hegedus, L.; Mattyasovszky, L.; Simon, A.; Simon, A.;
Kadas, I. Tetrahedron Lett. 2009, 50, 2857. (e) Szanto, G.; Hegedus, L.;
Mattyasovszky, L.; Simon, A.; Simon, A.; Bitter, I.; Toth, G.; Toke, L.;
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(f) Gabrielsen, B.; Monath, T. P.; Huggins, J. W.; Kefauver, D. F.; Pettit,
G. R.; Groszek, G.; Hollingshead, M.; Kirsi, J. J.; Shannon, W. M.;
Schubert, E. M.; Dare, J.; Ugarkar, B.; Ussery, M. A.; Phelan, M. J.
J. Nat. Prod. 1992, 55, 1569. (g) Pettit, G. R.; Ducki, S.; Eastham, S. A.;
Melody, N. J. Nat. Prod. 2009, 72, 1279.
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H.; Stubbe, M. Tetrahedron Lett. 1982, 23, 3171. (d) Paulsen, H.; Stubbe, M.
Liebigs Ann. Chem. 1983, 535. (e) Chida, N.; Ohtsuka, M.; Ogawa, S.
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Org. Lett. 2007, 9, 3683 (ent-lycoricdine).
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H.; Tanaka, H.; Tagaki, S.; Yakami, M.; Murata, M. Chem. Commun. 1975,
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(c) Moeller, O.; Steinberg, E. M.; Torssell, K. Acta Chem. Scand., Ser. B
1978, 32, 98. (d) Tsuda, Y.; Sano, T.; Taga, J. I.; Isobe, K.; Toda, J.; Takagi,
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Trans. 1 1979, 1358. (e) Umezawa, B.; Hoshino, O.; Sawaki, S.; Sashida, H.;
Mori, K. Heterocycles 1979, 12, 1475. (f) Sano, T.; Kashiwaba, N.; Toda, J.;
Tsuda, Y.; Irie, H. Heterocycles 1980, 14, 1097. (g) Martin, S. F.; Tu, C.-Y.
J. Org. Chem. 1981, 46, 3763. (h) Martin, S. F.; Tu, C.-Y.; Kimura, M.;
Simonsen, S. H. J. Org. Chem. 1982, 47, 3634. (i) Umezawa, B.; Hoshino, O.;
Sawaki, S.; Sashida, H.; Mori, K.; Hamada, Y.; Kotera, K.; Iitaka, Y.
Tetrahedron 1984, 40, 1783. (j) Boeckman, R. K.; Goldstein, S. W.; Walters,
M. A. J. Am. Chem. Soc. 1988, 110, 8250. (k) Hoshino, O.; Ishizaki, M.;
Kamei, K.; Tauchi, M.; Nagao, T.; Iwaoka, K.; Sawaki, S.; Umezawa, B.;
Iitaka, Y. Chem. Lett. 1991, 8, 1365. (l) Schultz, A. G.; Holoboski, M. A.;
Smyth, M. S. J. Am. Chem. Soc. 1996, 118, 6210 (ent-lycorine). (m) Hoshino,
O.; Ishizaki, M.; Kamei, K.; Tauchi, M.; Nagao, T.; Iwaoka, K.; Sawaki, S.;
Umezawa, B.; Iitaka, Y. J. Chem. Soc., Perkin Trans. 1 1996, 571. (n) Yamada,
K.; Yamashita, M.; Sumivoshi, T.; Nishimura, K.; Tomioka, K. Org. Lett. 2009,
11, 1631.
(8) Pancratistatin: (a) Danishefsky, S.; Lee, J. Y. J. Am. Chem. Soc. 1989,
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111, 4829. (b) Tian, X.; Hudlicky, T.; Konigsberger, K. J. Am. Chem. Soc.
1995, 117, 3643. (c) Trost, B. M.; Pulley, S. R. J. Am. Chem. Soc. 1995, 117,
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10143. (d) Hudlicky, T.; Tian, X.; Konigsberger, K.; Maurya, R.; Rouden, J.;
Fan, F. J. Am. Chem. Soc. 1996, 118, 10752. (e) Doyle, T. J.; Hendrix, M.;
VanDerveer, D.; Javanmard, S.; Haseltine, J. Tetrahedron 1997, 53, 11153.
(f) Magnus, P.; Sebhat, I. K. J. Am. Chem. Soc. 1998, 129, 5341.
(g) Rigby, J. H.; Maharoof, U. S. M.; Mateo, M. E. J. Am. Chem. Soc.
2000, 122, 6624. (h) Pettit, G. R.; Melody, N.; Herald, D. L. J. Org. Chem.
2001, 66, 2583. (i) Kim, S.; Ko, H.; Kim, E.; Kim, D. Org. Lett. 2002, 4, 1243.
(j) Li, M.; Wu, A.; Zhou, P. Tetrahedron Lett. 2006, 47, 3707. (k) Madsen, R.;
Dam, J. H. Eur. J. Org. Chem. 2009, 37, 4666.
(9) Narciclasine: (a) Rigby, J. H.; Mateo, M. E. J. Am. Chem. Soc. 1997,
119, 12655. (b) Keck, G. E.; Wager, T. T.; Rodriquez, J. F. D. J. Am. Chem.
Soc. 1999, 121, 5176. (c) Gonzalez, D.; Martinot, T.; Hudlicky, T. Tetra-
hedron Lett. 1999, 40, 3077. (d) Rigby, J. H.; Maharoof, U. S. M.; Mateo, M.
E. J. Am. Chem. Soc. 2000, 122, 6624. (e) Hudlicky, T.; Rinner, U.; Gonzalez,
D.; Akgun, H.; Schilling, S.; Siengalewicz, P.; Martinot, T. A.; Pettit, G. R.
J. Org. Chem. 2002, 67, 8726. (f) Elango, S.; Yan, T.-H. J. Org. Chem. 2002,
67, 6954. (g) Matveenko, M.; Banwell, M. G.; Willis, A. C. Tetrahedron 2008,
64, 4817 (ent-narciclasine, ent-lycoricidine).
(10) trans-Dihydronarciclasine: (a) Shin, I.-J.; Choi, E.-S.; Cho, C.-G.
Angew. Chem., Int. Ed. 2007, 46, 2303. (b) Jana, C. K.; Studer, A. Chem.;
Eur. J. 2008, 14, 6326. (c) Choi, E.-S.; Cho, C.-G. Tetrahedron. 2008, 64,
2172. By hydrogenation of narciclasine: (d) Mondon, A.; Krohn, K. Chem.
Ber. 1975, 108, 445. (e) Pettit, G. R.; Ducki, S.; Eastham, S. A.; Melody, N.
J. Nat. Prod. 2009, 72, 1279. (f) Szanto, G.; Hegedus, L.; Mattyasovszky, L.;
Simon, A.; Simon, A.; Kadas, I. Tetrahedron Lett. 2009, 50, 2857.
(11) Reviews: (a) Cook, J. W.; Loudon, J. D. In Alkaloids of the Amar-
yllidaceae, The Alkaloids; Manske, R. H. F., Holmes, H. L., Eds.; Academic
Press: New York, 1952; Vol. II, p 331. (b) Hartwell, J. L. Lloydia 1967, 30, 379.
(c) Wildman, W. C. In The Alkaloids; Manske, R. H. F., Ed.; Academic Press:
New York, 1968; p 307. (d) Fuganti, C. In The Alkaloids; Manske, R. H. F., Ed.;
Academic Press: New York, 1975; p 83. (e) Martin, S. F. In The Alkaloids; Brossi,
A. R., Ed.; Academic: New York, 1987; Vol. 40, p 251. (f) Polt, R. In Organic
Synthesis: Theory and Applications; Hudlicky, T., Ed.; JAI Press: Greenwich,
CT, 1997; Vol. 3, p 109. (g) Ruan, L. Yaoxue Tongbae 1988, 23, 453. (h) Hoshino,
O. In The Alkaloids; Cordell, G. A., Ed.; Academic: New York, 1998; Vol. 51,
p 323. (i) Rinner, U.; Hudlicky, T. Synlett 2005, 365. (j) Chapleur, Y.; Chretien, F.;
Ahmed, I.; Khaldi, M. Curr. Org. Synth. 2006, 3, 331. (k) Kornienko, A.;
Evidente, A. Chem. Rev. 2008, 108, 1982. (l) Manpadi, M.; Kornienko, A. Org.
Prep. Proced. Int. 2008, 40, 107. (m) Jin, Z. Nat. Prod. Rep. 2009, 26, 363.
(6) 7-Deoxypancratistatin: (a) Ohta, S.; Kimoto, S. Chem. Pharm. Bull.
1976, 24, 2969. (b) Ohta, S.; Kimoto, S. Chem. Pharm. Bull. 1976, 24, 2977.
(c) Paulsen, H.; Stubbe, M. Liebigs Ann. Chem. 1983, 535. (d) Tian, X.;
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Maurya, R.; Konigsberger, K.; Hudlicky, T. Synlett 1995, 1125. (e) Keck,
G. E.; McHardy, S. F.; Murry, J. A. J. Am. Chem. Soc. 1995, 117, 7289.
(f) Chida, N.; Jitsuoka, M.; Yamamoto, Y. Heterocycles 1996, 43, 1385.
(g) Keck, G. E.; Wagner, T. T.; McHardy, S. F. J. Org. Chem. 1998, 63, 9164.
(h) Keck, G. E.; McHardy, S. F. J. Org. Chem. 1999, 64, 4465. (i) Akg€un, H.;
Hudlicky, T. Tetrahedron Lett. 1999, 40, 3081 (ent-7-deoxypancratistatin).
(j) Acena, J. L.; Arjona, O.; Leon, M. L.; Plumet, J. Org. Lett. 2000, 2, 3683.
(k) Padwa, A.; Zhang, H. Tetrahedron Lett. 2006, 47, 3905. (l) Hakansson, A. E.;
Palmelund, A.; Holm, H.; Madsen, R. Chem.;Eur. J. 2006, 12, 3243.
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found such compounds completely inactive.21 From the
results of biological testing of these derivatives it became
evident that full hydroxylation and trans-fused ring junction
are essential for activity. Furthermore, the donor-acceptor
functionality of pancratistatin is also essential for activity,
which is greatly diminished in the constituents lacking the
C-7 phenol. Finally, the efforts of Gabrielsen22 established
that the Amaryllidaceae constituents also exhibit antiviral
activity. It may very well be that the amino mannose con-
figuration of the amino inositol ring is responsible for such
biological activity. To complete the activity testing of the
Amaryllidaceae constituents will require supply of the com-
pounds from sources other than isolation.
The first goal, the attainment of practicality, would re-
quire a total synthesis of less than eight steps as well as
serious optimization, and so far this requirement would seem
out of reach as the shortest of our syntheses is 11 steps long.
To reach the second goal we have to date prepared a number
of truncated derivatives that did display moderate activities
when tested against the standard human cancer cell lines.
The quest for both of the defined goals is now in its eighth
generation. In this paper we report a concise chemo-
enzymatic synthesis of several C-1 derivatives of 7-de-
oxypancratistatin by an efficient strategy involving the
phenanthrene-phenanthridone transform via oxidative clea-
vage and recyclization. Two of the derivatives displayed high
and promising activities, which are reported herein. In
addition, formal total syntheses of 7-deoxypancratistatin
and trans-dihydrolycoricidine have also been completed.
FIGURE 2. Proposed pharmacophore of pancratistatin.
aims at the design and synthesis of unnatural derivatives of
Amaryllidaceae constituents that would have improved solu-
bility and bioavailability with full retention or even enhance-
ment of activities.
The pioneering research of Pettit on the investigation of
biological activities of Amaryllidaceae constituents have
eventually led to a proposal for the essential pharmacophore
of pancratistatin as depicted in Figure 2.
The currentefforts of our group, McNulty, and Kornienko
have produced many unnatural derivatives of pancratistatin,
some with modest activities. For example, McNulty investi-
gated the importance of hydroxylation12 and constitution13
of the aminoinositol ring. Kornienko has also explored
various truncations of the C ring.14 In the course of their
semisynthesis of pancratistatin, Pettit and co-workers gen-
erated a C-1 benzoyl derivative of pancratistatin that dis-
played remarkably potent activity.8h In an effort to improve
the aqueous solubility of various Amaryllidaceae constitu-
ents, the Pettit group has synthesized 7-O-phosphate pro-
drug analogues of 2,15 3,4-O-cyclic phosphate analogues of 2
and 4-7, and the C-1 benzoyl analogue.16 These phos-
phate prodrugs are currently being evaluated on a preclinical
level. We have prepared an indole mimic of 7-deoxypancra-
tistatin,17 several truncated derivatives,18 a cis-fused epimer
of 7-deoxypancratistatin,19 which was completely devoid of
activity, and bis-trimethylsilyl analogues20 attained by cobalt-
catalyzed cyclotrimerization of acetylene-equipped scaffolds.
Chapleur prepared lactone analogues of lycoricidine and
Results and Discussion
Almost 20 years ago we implemented a general chemo-
enzymatic strategy toward the four major Amaryllidaceae
constituents. The design for lycoricidine and narciclasine
envisioned the generation of the aminocoduritol moiety via
hetero-Diels-Alder reaction of cis-dihydrodiols such as 8
and 10, derived from bromobenzene and m-dibromoben-
zene, respectively. The introduction of the aryl fragment then
relied on an appropriate Heck or Suzuki coupling, Figure 3.
For the more highly functionalized pancratistatin and its
7-deoxy congener, attachment of the aryl residue was per-
formed by the nucleophilic opening of aziridine 14 or its
N-tosyl derivative. These two strategies yielded the total
syntheses of these alkaloids in reasonably short sequences,
further improved in subsequent generations. An additional
strategy for 7-deoxypancratistatin was implemented via
cobalt-catalyzed cyclotrimerization of a fully functionalized
amino inositol scaffold 15 yielding the TMS derivative of 7-
deoxypancratistatin 16. Solid-phase silica-gel-catalyzed re-
action of indole with aziridine 18 led to the preparation of the
indole mimic of the Amaryllidaceae constituent, namely, 19.
It was the success of the solid-phase synthesis that provided
for the latest design for 7-deoxypancratistatin via the intra-
molecular opening of aziridine 20, which provided phenan-
threne 21 whose oxidative cleavage and recyclization yields,
after full deprotection, C-1 derivatives, such as the aldehyde
22, suitable for further functionalization to unnatural deriva-
(12) (a) McNulty, J.; Mao, J.; Give, R.; Mo, R.; Wolf, S.; Pettit, G. R.;
Herald, D. L.; Boyd, M. R. Bioorg. Med. Chem. Lett. 2001, 11, 169.
(b) McNulty, J.; Larichev, V.; Pandey, S. Bioorg. Med. Chem. Lett. 2005,
15, 5315.
(13) McNulty, J.; Nair, J. J.; Griffin, C.; Pandey, S. J. Nat. Prod. 2008, 71,
357.
(14) Manpadi, M.; Kireev, A. S.; Magedov, I. V.; Altig, J.; Tongwa, P;
Antipin, M. Y.; Evidente, A.; van Otterlo, W. A. L.; Kornienko, A. J. Org.
Chem. 2009, 74, 7122.
(15) (a) Pettit, G. R.; Freeman, S.; Simpson, M. J.; Thompson, M. A.;
Boyd, M. R.; Williams, M. D.; Pettit, G. R., III; Doubek, D. L. Anti-Cancer
Drug Des. 1995, 10, 243–250. (b) Pettit, G. R.; Orr, B.; Ducki, S. Anti-Cancer
Drug Des. 2000, 15, 389–395.
(16) (a) Pettit, G. R.; Melody, N.; Simpson, M.; Thompson, M.; Herald,
D. L.; Knight, J. J. Nat. Prod. 2003, 66, 92. (b) Pettit, G. R.; Melody, N.;
Herald, D. L. J. Nat. Prod. 2004, 67, 322. (c) Pettit, G. R.; Melody, N. J. Nat.
Prod. 2005, 68, 207. (d) Shnyder, S. D.; Cooper, P. A.; Millignton, N. J.; Gill,
J. H.; Bibby, M. C. J. Nat. Prod. 2008, 71, 321.
(17) (a) Hudlicky, T.; Rinner, U.; Finn, K. J.; Ghiviriga, I. J. Org. Chem.
2004, 70, 3494. (b) Rinner, U.; Hudlicky, T.; Gordon, H.; Pettit, G. R.
Angew. Chem., Int. Ed. 2004, 43, 5342.
(18) Rinner, U.; Hillebrenner, H. L.; Adams, D. R.; Hudlicky, T.; Pettit,
G. R. Bioorg. Med. Chem. Lett. 2004, 14, 2911.
(19) (a) Rinner, U.; Siengalewicz, P.; Hudlicky, T. Org. Lett. 2002, 4, 115.
(b) Hudlicky, T.; Rinner, U.; Gonzalez, D.; Akgun, H.; Schilling, S.;
Siengalewicz, P.; Martinot, T. A.; Pettit, G. R. J. Org. Chem. 2002, 67, 8726.
(20) (a) Moser, M.; Sun, X.; Hudlicky, T. Org. Lett. 2005, 7, 5669.
(b) Moser, M.; Banfield, S. C.; Rinner, U.; Chapuis, J.-C.; Pettit, G. R.;
Hudlicky, T. Can. J. Chem. 2006, 84, 1313.
(22) Gabrielsen, B.; Monath, T. P.; Huggins, J. W.; Kefauver, D. F.;
Pettit, G. R.; Groszek, G.; Hollingshead, M.; Kirsi, J. J.; Shannon, W. M.;
Schubert, E. M.; Dare, J.; Ugarkar, B.; Ussery, M. A.; Phelan, M. J. J. Nat.
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FIGURE 3. Evolution of diverse strategies toward Amaryllidaceae constituents.
tives. The entire strategy aimed at the synthesis of aldehyde 22
was based on the expectation that extended functionalization of
the C-1 alcohol in 7-deoxypancratistatin would be arduous
because of the dense substitution of the amino inositol ring.
Synthesis of 7-Deoxypancratistatin C-1 Carboxaldehyde.
The synthesis of this key aldehyde begins with diol 8, pro-
duced by fermentation of bromobenzene with E. coli JM 109
(pDTG601),23 protected as its acetonide, and subjected to
the Yamada-Jacobsen-Evans protocol of aziridination24
to yield the known N-tosyl aziridine 24,25 used in previous
generations of pancratistatin synthesis, Scheme 1.
Dehalogenation of the vinyl bromide (n-Bu3SnH, AIBN,
76%) produced cleanly vinyl-aziridine 18 whose epoxidation
with m-CPBA furnished epoxy aziridines 25a and 25b in 96%
yield as a 3:1 mixture of diastereomers. Successive recrystal-
lizations from isopropyl alcohol allowed for enrichment of
the ratio up to 10:1 (25a:25b), but in general two recrystalli-
zations provided a workable ratio of 7:1. Addition of the
mixture of epoxy aziridines to the alane derived from aryl
acetylene 26 (n-BuLi, Me2AlCl, -50 to 0 °C) produced an
intermediate acetylenic alcohol that was immediately pro-
tected to give its silyl ether 27 (TBDMSOTf, Et3N, -78 °C,
77%). Initial attempts at the epoxide opening provided the
desired product in poor yield, and further investigation
revealed that strict control of temperature, both in the
formation of the alane and in the addition of the epoxide,
was necessary to attain reproducible yields. Deviation from
(23) Zylstra, G. J.; Gibson, G. T. J. Biol. Chem. 1989, 264, 14940.
(24) (a) PhIdNTs is prepared according the procedure of Yamada:
Yamada, Y.; Yamamoto, T.; Okawara, M. Chem. Lett. 1975, 361. (b) Evans,
D. A.; Faul, M. M.; Bilodeau, M. T. J. Org. Chem. 1991, 56, 6744.
(25) See refs 6d, 8b, and 8d.
3072 J. Org. Chem. Vol. 75, No. 9, 2010

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SCHEME 1
this protocol led to decreased yields, attributed to either the
incomplete formation of the alane or various side reactions
of the epoxy aziridine. Predominant side products included
those derived from the nucleophilic opening of the aziridine
and/or epoxide with chloride anion as well as opening of the
aziridine with the alkyne (structures are not shown). It was
also discovered that for complete conversion of the epoxy
aziridine 2 equiv of the alane was required. Fewer equiva-
lents of the alane resulted in incomplete conversion of
starting material, and more equivalents yielded increased
production of the byproducts mentioned above. Silyl ether
27 was subjected to either the Lindlar hydrogenation proto-
col (Lindlar’s catalyst, quinoline, 94%) or treatment with dicy-
clohexylborane (BH3/SMe2, cyclohexene, 0 °C, 76%) followed
by protonolysis to afford the required cis-alkene 20, Scheme 1. In
the absence of quinoline, this hydrogenation protocol provided
mixtures of alkene 20 and its fully reduced alkane 28.
as shown in Figure 4. First, the complete assignments of the
1
1H and 13C chemical shifts were made based on the H-1H
and 1H-13C (one-bond and long-range) couplings seen
in the DQCOSY, gHMQC, and gHMBC spectra, corre-
spondingly. The connectivity in 37 was confirmed during this
assignment.
Adsorption of the aziridine on activated silica followed by
heating at 120 °C under argon for 24 h provided, after elution
of the material with hexanes/ethyl acetate, 8:1-5:1, the key
phenanthrene skeleton 21 in 74% yield, Scheme 2. Oxidative
cleavage of this material was investigated in detail, and
several methods were compared for overall efficiency in the
generation of the dialdehyde 31.
Osmylation of 21 produced the required cis-diol 29 as a
mixture with overoxidized keto alcohol 30 (OsO4, NMO, rt)
This crude mixture was reduced completely to cis-diol 30
(NaBH4, dioxane/EtOH, rt) before the oxidative cleavage
with periodate to dialdehyde 31 (NaIO4, dioxane/H2O, rt,
83% over 3 steps). The use of excess equivalents of co-
oxidant (NMO) in the osmylation step allowed for isolation
of hydroxy ketone 30 as the sole product in 89% yield.
The complete assignment of stereochemistry in 30 was
determined by extensive NMR analysis of its acetate 37,
FIGURE 4. Full assignment of stereochemistry for the acetate 37,
derived from hydroxy ketone 30. (For clarity, the tosyl group was
removed in the 3D model).
The stereochemistry of 37 was inferred from 1H-1H
coupling constants and confirmed by NOEs. The coupling
constant between 2.57 and 2.99 is 4.2 Hz, which means that
the junction of rings B and C is cis; 4.77 and 2.57 have a
coupling constant of 13.3 Hz, and therefore they are both
axial on ring B. The conformation of ring C is chair, as
demonstrated by the NOE of 1.30 with 4.25, which is much
larger than the NOE of 1.30 with 4.10. Also, 1.37 has large
NOEs with both 3.76 and 4.77; 3.76 couples with 2.99 and
4.10 with coupling constants of 12.3 and 8.7 Hz, respectively,
and therefore they are all axial on ring C. Both 2.57 and 4.25
are equatorial on ring C, and as expected, their coupling
J. Org. Chem. Vol. 75, No. 9, 2010 3073

Collins et al.
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SCHEME 2
constants with 5.82 are small. The NOE of 5.82 with 4.77
demonstrates that 5.82 is cis to ring B.
A potentially more efficient route to acid 34 was envi-
sioned via direct ozonolysis of phenanthrene 21 followed by
oxidative workup. This transformation was indeed attemp-
ted by means of ozonolysis followed by an oxidative workup,
and a mixture of carboxylate derivatives 33 was obtained,
composed of diacids and diesters, as well as monoacid/
monoesters), as indicated in Scheme 2. Upon warming of
the reaction mixture cyclization of the various derivatives 33
to phenanthridones 34 and 35 occurred in low yields, inferior
to those obtained via dialdehyde 31.
Synthesis of C-1 Derivatives of 7-Deoxypancratistatin. In
the course of Pettit’s relay synthesis of pancratistatin the
activity studies of a C-1 benzoate ester, derived from narci-
clasine, were reported.8h This C-1 analogue was shown to
possess potent activity, particularly against the murine leu-
kemia cell line (ED50 0.0017 μg/mL). This activity is compar-
able to that of narciclasine (ED50 0.0044 μg/mL) and an
order of magnitude greater than that of pancratistatin (ED50
0.032 μg/mL) against the same cell line. We therefore set out
to make several C-1 derivatives of 7-deoxypancratistatin that
we could evaluate for biological activity. This anticancer
activity could then be compared with the known data for 7-
deoxypancratistatin, itself generally an order of magnitude
less active than pancratistatin. Should such activities show
promise a full scale lead optimization would then be under-
taken. A reasonable first choice seemed to be the synthesis
and evaluation of the C-1 aldehyde and the corresponding
acid and ester, as well as the C-1 hydroxymethylene and its
acetate. The synthesis of these compounds was relatively
Hydroxy ketone 30 was then converted to dialdehyde 31
by the same reduction-oxidative cleavage sequence as de-
scribed above. At room temperature, dialdehyde 31 ap-
peared to be a complex mixture of phenanthridol 32 and
1
various atropoisomers of dialdehyde 31 (vide H NMR).
Oxidation of 32 allowed for ready conversion to the
complete phenanthridone skeleton of 7-deoxypancratistatin,
C-1 aldehyde 22 (IBX, DMF, rt, 61% from 30). We had
initially intended to oxidize aldehyde 22 with m-CPBA
directly to formate 36, a protected form of 7-deoxypancra-
tistatin. This attempt was based on relatively few reports in
the literature describing a Baeyer-Villiger oxidation of
cyclohexane carboxaldehyde to the corresponding for-
mate;26 most other aliphatic aldehydes are known to yield
carboxylic acids.27 In this case, the oxidation with buffered
m-CPBA in dichloromethane led in 85% yield to the C-1
acid 34, which was converted to its methyl ester 35 with
diazomethane in 83% yield.
(26) (a) Royer, J.; Beugelmans-Verrier, M. C. R. Hebd. Seances. Acad.
Sci. Ser. C 1971, 272, 1818. (b) Royer, J.; Beugelmans-Verrier, M. C. R.
Hebd. Seances. Acad. Sci. Ser. C 1974, 279, 1049. (c) Buchbauer, G.; Heneis,
V. M.; Krejci, V.; Talsky, C.; Wunderer, H. Monatsh. Chem. 1985, 116,
1345. (d) Hagiwara, H.; Akama, T.; Uda, H. Chem. Lett. 1989, 11, 2067.
(e) Margot, C.; Simmons, D. P.; Reichin, D.; Skuy, D. Helv. Chim. Acta 2004,
87, 2662.
(27) For a review of Baeyer-Villiger oxidations, see: Krow, G. R. Org.
React. 1993, 43, 251.
3074 J. Org. Chem. Vol. 75, No. 9, 2010

Collins et al.
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SCHEME 3
straightforward and is shown in Scheme 3. Thus ester 35 was
subjected to detosylation to phenanthridone 38 (Na/naphth-
alene, -58 °C, 58%), whose deprotection (3%HCl in MeOH,
69%) provided the fully hydroxylated ester 39. Base-
catalyzed hydrolysis (LiOH, rt, 95%) furnished the
corresponding acid 40. The aldehyde 22 was reduced to
alcohol 41 (NaBH4, 0 °C, 85%). In this case, reduction
reactions performed above 0 °C resulted in competitive
reduction of the activated phenanthridone. The alcohol
41 was further converted to its acetate 42 (Ac2O, pyridine,
DMAP, 81%) prior to detosylation. Phenanthridone 43
was converted without isolation to alcohol 44 (TBAF,
0 °C, 74% over 2 steps). Exhaustive hydrolysis of this
compound (K2CO3 then 3% HCl in MeOH, 75%) gave the
completely hydroxylated derivative 45, while the acid-
catalyzed deprotection (3% HCl in MeOH, 45%) furn-
ished the C-1 acetoxymethylene derivative 46. Four of
these compounds, the C-1 acid 40, its methyl ester 39,
and the hydroxymethylene derivatives 45 and 46 were sub-
jected to screening against the human cancer cell lines (see the
last section for the summary of biological activities).
Baeyer-Villiger oxidaton was disappointing as that manou-
ver would have led to the shortest synthesis of 7-deoxypan-
cratistatin to date. Wehaveattempted to convert the aldehyde
and the silyl ether functionalities in 22 to an olefin, which
would correspond to a formal synthesis of 7-deoxypancratis-
tatin, but a set of very unusual problems was encountered.
First, the oxidative decarboxylation employed by Wender
in his synthesis of retigeranic acid28 failed to produce the
olefin from the β-hydroxy acid derived from 34 by removal of
the silyl protecting group. Second, we attempted the creation
of the olefin via oxetane, as was done by Grieco in his
synthesis of compactin,29 and followed Nicolaou’s three-
step protocol,30 utilized in his taxol synthesis, for oxetane
generation from 1,3-diol derived from 34. Neither strategy
met with success and we attempted the conversion of acid 34
to the C-1 bromide via Hunsdiecker reaction, also to no
(28) (a) Wender, P. A.; Singh, S. K. Tetrahedron Lett. 1990, 31, 2517.
(b) Tauchi, H.; Yamamoto, H.; Nozaki, H. Tetrahedron Lett. 1975, 19, 1545.
(29) Grieco, P. A.; Zelle, R. E.; Lis, R.; Finn, J. J. Am. Chem. Soc. 1983,
105, 1403.
(30) (a) Nicolaou, K. C.; Yang, Z.; Liu, J. J.; Ueno, H.; Nantermet, P. G.;
Guy, R. K.; Clairborne, C. F.; Renaud, J.; Couladouros, E. A.; Paulvannan,
K.; Sorensen, E. J. Nature 1994, 367, 630. (b) Nicolaou, K. C.; Ueno, H.; Liu,
J.-J.; Nantermet, P. G.; Yang, Z.; Renaud, J.; Paulvannan, K.; Chadha, R.
J. Am. Chem. Soc. 1995, 117, 653.
Formal Synthesis of 7-Deoxypancratistatin and Total Syn-
thesis of trans-Dihydrolycoricidine. The failure to produce
formate 36 directly from the protected aldehyde 22 by
J. Org. Chem. Vol. 75, No. 9, 2010 3075

Collins et al.
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SCHEME 4
avail. Conversion of the C-1 aldehyde in 22 to the methyl
ketone and Baeyer-Villiger oxidation of the latter led
cleanly to methyl ester 35, accompanied by the lactone
derived from the ester and C-3 hydroxyl as a result of the
acetonide hydrolysis. Base-catalyzed elimination of the β-
silyloxy group from either acid 34 or ester 35 did not lead to
the corresponding unsaturated carbonyl compound; the
inertness of the C-1/C-2 functionalities to the above variety
of conditions remains unexplained.
cell lines in vitro. While the C-1 acid 40 and its methyl ester 39
were found inactive, the hydroxymethyl analogue 45 and its
acetate 46 displayed useful levels of activity. Therefore, to
assess their potential, these two compounds were further
evaluated for antiproliferative activities in a panel of human
cancer cell lines. In addition, their ability to induce apoptosis in
human leukemia and neuroblastoma cells was also examined.
Cancer Cell Line Growth Inhibitory Activities. Table 1
provides the antiproliferative potencies of several relevant
Amaryllidaceae constituents, compounds 45 and 46, and
synthetic C-1 benzoyl derivatives 51 and 52, previously
synthesized by Pettit’s group and found to be the most potent
Amaryllidaceae isocarbostyril analogues identified to date.
Although the C-1 analogues 45 and 46 provide antipro-
liferative potencies somewhat inferior to those of the natural
isocarbostyrils pancratistatin and narciclasine, this fact is
consistent with the overriding influence of the 7-hydroxyl
phenolic functionality, present in 2 and 4 but not in 45 and
46. However, these compounds appear to be at least as good
as or better than 7-deoxypancratistatin, pointing to the
beneficial effect of the C-1 derivatization. Furthermore, it
appears that large lipophilic C-1 substituents are preferred,
whereas elevated polarity at C-1 is not tolerated. Indeed, the
C-1 acid 40 and its methyl ester 39 (presumably undergoing
intracellular hydrolysis to 40) are inactive, whereas acetate
46 is somewhat more potent than the parent alcohol 45.
These findings are consistent with the beneficial effect of the
C-1 benzoyl moiety in 51 as found by Pettit. It is not entirely
clear at this point whether the benzoyl in 51 and the acetyl in
46 are part of the pharmacophore or if they merely assist the
parent hydroxyl compounds in cell penetration and then
undergo intracellular hydrolytic removal. The answer to this
question will have to await further studies involving the
preparation and testing of analogues with nonhydrolyzable
large lipophilic substituents at C-1.
Having failed in the manipulations of functional groups in
aldehyde 22 or the acid 34, we subjected 22 to Wilkinson
decarbonylation (RhCl(PH3)3, toluene, 130 °C) to produce
47, which was smoothly detosylated to phenanthridone 48
(Na/naphthalene, -78 °C, 74% over 2 steps) (Scheme 4).
Treatment of 48 with acidic methanol (3% HCl, MeOH,
71%) allowed for hydrolysis of the remaining protecting
groups and completed the total synthesis of trans-dihydro-
lycoricidine (7) ([R]22D 28.6 (c 0.25, DMSO), lit.31 [R]25D 138
(c 0.96, DMSO). The formal total synthesis of 7-deoxypan-
cratistatin was also completed by first protection of lactam
48 (NaH, PMBBr, 0 °C) as its p-methoxybenzyl derivative
followed by cleavage of the silyl ether (TBAF, 0 °C, 64% over
2 steps) yielding alcohol 49. Chugaev elimination of the C-2
alcohol (NaH, CS2, MeI, xylenes, 165 °C, 35%) provided
olefin 50, an intermediate in Padwa’s synthesis of 7-deoxy-
pancratistatin (mp 172-174 °C (ethyl acetate/hexanes), lit.
171-173 °C).4m A more direct route to 7-deoxypancratista-
tin was envisioned by the oxidative cleavage of trimethylsilyl
enol ether derived from 22 followed by deprotection of the
C-3 silyl ether and a directed reduction of the C-1 carbonyl
(NaBH4, EtOH). This protocol, performed in a preliminary
manner, yielded the C-1/C-2 diol, leaving only the detosyla-
tion and hydrolysis to provide 3 in a shorter sequence.
Biological Evaluation of C-1 Derivatives. To date the search
for a more active or more bioavailable synthetic analogue of
the Amaryllidaceae constituents has yielded relatively few
compounds that showed promise. In continuation of this effort
the novel C-1 analogues of 7-deoxypancratistatin, synthesized
in this work, were evaluated for antitumor activities in cancer
Apoptosis Induction. Apoptotic morphology was observed
in Jurkat and SH-SY5Y cells after 72 h of treatment with
compound 45 or 46 (Figure 5) through Hoechst staining and
Annexin-V binding. The effective dose at which 50% of cells
were apoptotic (ED50) for compound 45 in Jurkat cells was
1 μM and in SH-SY5Y cells was 10 μM. Compound 46 had
greater apoptotic efficacy than 45 in both Jurkat and SH-
(31) Pettit, G. R.; Pettit, G. R., III; Backhaus, R. A. J. Nat. Prod. 1993,
56, 1682.
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TABLE 1. Human Cancer Cell Line and Murine P-388 Lymphocytic Inhibitory Activities (ED50, μg/mL)
leukemia
P388
pancreas
BxPC-3
breast
MCF-7
CNS
SF-268
lung-NSC
NCI-H460
colon
KM20L2
prostate
DU-145
leukemia
Jurkat
neuroblastoma
Shsy5y
compd
2
3
0.039
0.44
0.028
0.032
0.017
0.048
0.29
0.062
0.22
0.016
0.163
0.163
4
7
51
52
45
46
0.001
0.029
0.0016
0.061
0.026
0.046
0.0019
0.25
0.19
0.11
0.019
0.034
0.00031
0.041
0.65
0.021
0.059
0.00055
0.17
0.032
0.043
0.0001
0.029
0.09
0.021
0.051
0.00037
0.13
0.011
0.040
0.00021
0.13
0.26
0.37
1.615
0.183
1.615
0.183
0.29
0.11
SY5Y cells, as the ED50 was determined to be 0.5 μM for
both cell types (Figure 6). This indicates that 46, much like 2,
has the ability to induce apoptosis specifically in cancerous
cells. Most importantly, compound 46 did not induce apop-
tosis in noncancerous normal human cells such as normal
human fibroblasts (NHFs) and peripheral mononucleated
blood cells (PMBC) prepared from blood obtained from
healthy volunteers (Figure 7). These results indicate that com-
pound 46 is selectively targeting cancer cells to induce apoptosis
and could be a safer alternative to toxic chemotherapy.
Conclusions
We have completed a short and potentially practical
synthesis of several C-1 derivatives of 7-deoxypancratistatin,
two of which (45 and 46) exhibited promising biological
activities in several cell lines as well as in apoptosis screens.
Given that these compounds, lacking the crucial 7-hydroxyl
group, exhibited good activities, it stands to reason that the
next step in this program should be the evaluation of the
corresponding C-1 acetoxymethyl and related compounds
that contain the otherwise complete pharmacophore of
pancratistatin. We would expect that such derivatives should
equal the natural product in potency and would therefore
provide the rationale for further lead optimization toward
more soluble and bioavailable derivatives. As a side benefit, a
total synthesis of trans-dihydrolycoricidine 7 was accom-
plished from aldehyde 22 along with a formal total synthesis
of 7-deoxypancratistatin.
FIGURE 5. Hoechst cell-permeable dye and Annexin-V binding
were used to observe nuclear morphology after exposure to comp-
ound 45 or 46. Cells with brightly stained, condensed nuclei are con-
sidered to be apoptotic (a). Apoptosis was confirmed by Annexin-V
binding after 48 h exposure to either 45 or 46 at 0.5 μM (b).
Experimental Section
Cell Culture. The human neuroblastoma (SH-SY5Y) and
B-cell leukemia (Jurkat) cell lines were purchased from ATCC
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Collins et al.
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FIGURE 7. Compound 46 does not induce apoptosis in noncan-
cerous human cells. Normal human fibroblasts (NHFs) and non-
cancerous peripheral blood mononuclear cells (ncPBMCs) were
treated with compound 46 and stained with Hoechst as described in
the Experimental Section. Apoptotic nuclear morphology is not
visible in NHFs or PMBC prepared from blood obtained from
healthy volunteers after treatment with 46.
DMEM (Cellgro) supplemented with 10% FBS, 100 mg/L
penicillin G, and 100 mg/L streptomycin. Human mammary
carcinoma cells MCF-7 (ATCC no. HTB-22) were cultured
using DMEM supplemented with 10% FBS, 100 mg/L penicillin
G, 100 mg/L streptomycin, 1.0 mM glutamax, and 1.0 mM
sodium pyruvate, (Gibco).
Peripheral blood was obtained from healthy nonsmoking
volunteers aged 25-50 y upon written and informed consent
(University of Windsor REB no. 04-147). Whole blood samples
were collected in BD Vacutainer cell preparation tubes, and
mononuclear cells were separated by density gradient centrifu-
gation. The isolated cells were maintained in RPMI 1640 media
supplemented and maintained as was the Jurkat culture.
MTT Assay. To evaluate the cytotoxic effects of the C-1
derivatives of 7-deoxypancratistatin, mitochondrial dehydro-
genase activities were measured. Jurkat and SH-SY5Y cells were
grown and treated for 24, 48, and 72 h. Cells were treated with
concentrations ranging from 0.25 to 10 μM of each derivative
dissolved in DMSO. Similarly, ncPBMCs and NHFs were
treated to assess the effects of the C-1 derivatives on noncancer-
ous cells .
In addition, the BxPC-3, CRL-1687, DU-145, and MCF-7
lines were assessed by seeding 4 ꢀ 103 cells per well into
microplates. The cells were grown for 24 h before treatment at
concentrations ranging from 0.01 to 10 μM and incubated for
48 h. MTT reagent (5 mg/mL, MP Biomedical, Solon, OH) was
added to each well and incubated further for 2 h. The resulting
formazan crystals were dissolved in DMSO, and the OD was
determined at a wavelength of 490 nm. The experiments were
repeated at least twice for each compound per cell line. Cells
treated with 0.1% DMSO were used as a control.
FIGURE 6. Apoptosis is induced by compounds 45 (a) and 46 (b) in
Jurkat and SH-SY5Y cells after 72 h of exposure. Cells were stained
with Hoechst dye and counted to determine the percentage of
apoptotic cells; a minimum of 5 fields containing at least 100 cells
per field were counted.
(Manassas, VA). Cells were maintained and grown at 37 °C,
95% humidity and 5% CO2. Jurkat cells were grown with
RPMI-1640 media (Sigma-Aldrich, Oakville, ON, Canada)
supplemented with 10% fetal bovine serum (FBS) and 10 mg/mL
gentamycin (Gibco BRL, Mississauga, ON, Canada). SH-SY5Y
cells were grown with Dulbecco’s Modified Eagles Medium
(DMEM) HAM F12 (Sigma-Aldrich), supplemented with
2 mM L-glutamine, 10 mg/mL gentamycin, and 10% FBS.
Normal human fibroblasts (NHFs) obtained from Coriell
Institute for Medical Research (New Jersey, USA) were cultured
in Earle’s Minimum Essential Medium (MEME) (Sigma Chemical
Company, Mississauga, Ontario, Canada) completed with 15%
fetal bovine serum, 2 mM L-glutamine, 10 mg/mL gentamycin,
1.5 g/L sodium bicarbonate, 1% vitamins, and essential
(2%) and nonessential amino acids (1%) (Gibco BRL, VWR,
Mississauga, ON, Canada).
Human nonsmall cell lung cancer line NCI-H460 (ATCC no.
HTB-177) and human pancreatic adenocarcinoma cancer cell
line BxPC-3 (ATCC no. CRL-1687) were cultured in RPMI-
1640 medium supplemented with 10% fetal bovine serum (FBS)
(Gibco, Carlsbad, CA), 100 mg/L penicillin G, and 100 mg/L
streptomycin and (Cellgro, Manassas, VA). Human prostate
carcinoma cells DU-145 (ATCC no. HTB-81) were cultured in
Cellular Staining. Nuclear morphology was visualized using a
final concentration of 10 μM Hoechst 33342 dye (Molecular
Probes, Eugene, OR, USA). Phosphatidyl serine flipping (an
apoptotic biochemical marker) was visualized with Annexin-V-
FITC binding assay as per manufacturer’s protocol (Molecular
Probes, Eugene OR, USA). Cells were observed with a fluor-
escent microscope (Leica DM IRB, Germany); apoptotic in-
dices were determined by counting brightly stained condensed
nuclei (apoptotic cells) from at least 5 fields at 40X objective.
3078 J. Org. Chem. Vol. 75, No. 9, 2010

Collins et al.
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Apoptotic cells were expressed as a percentage of the total
number of cells counted. Standard error was calculated from
at least 3 separate experiments.
(1S,2R,3R,4R,5S,6R)-3,4-(Isopropylidenedioxy)-5-[(tert-butyl-
dimethylsilyl)oxy]-6-2-benzo[1.3]dioxol-5-ylethynyl-(40-methyl-
phenylsulfonyl)-7-azabicyclo[4.1.0]heptanes (27). To a solution
of acetylene 26 (0.43 g, 2.96 mmol) in 8 mL of dry toluene at
-50 °C was added 1.46 mL of a solution of nBuLi in hexanes
(2.01 M, 2.96 mmol) over 5 min. The solution was stirred for
15 min before 2.97 mL of a solution of Me2AlCl (1.0 M in
CH2Cl2, 2.96 mmol) was added dropwise over 10 min. The
reaction flask was kept at -50 °C for 0.5 h and then moved to an
ice bath and stirred an additional 0.5 h before being allowed to
warm to room temperature and stir for 0.5 h. The reaction flask
was then cooled to -20 °C, and 8 mL of a solution of epoxide
25a:25b (7:1 mixture of isomers) (0.5 g, 1.48 mmol) in toluene
was added dropwise over 20 min before being allowed to slowly
warm to room temperature over 5 h. The reaction mixture was
cooled in an ice bath and quenched with 1 M HCl (1 mL). Ethyl
acetate (50 mL) was added, and the layers were separated. The
aqueous phase was extracted with 3 ꢀ 50 mL EtOAc, and the
combined organic layers were dried over Na2SO4. Concentra-
tion under reduced pressure gave 0.883 g of crude alcohol
intermediate, which was immediately subjected to protection
protocol. A small sample for characterization was purified by
flash column chromatography (hexanes/ethyl acetate, 7:1 to 4:1)
afforded alcohol (3aS,4R,5R,6R,7S,7aR)-6-(1,3-benzodioxol-
5-ylethynyl)-2,2-dimethyl-8 [(4-methylphenyl)sulfonyl]hexahydro-
4,5-epimino-1,3-benzodioxol-7-ol as a clear and colorless oil;
General Experimental Details. All nonhydrolytic reactions
were carried out under an argon atmosphere. Glassware used
for moisture-sensitive reactions was flame-dried under vacuum
and subsequently purged with argon. THF, DME, and toluene
were distilled from potassium/benzophenone. Methylene chlor-
ide and acetonitrile were distilled from calcium hydride. Flash
column chromatographywas performed using Kieselgel60 (230-
400 mesh). Analytical thin-layer chromatography was per-
formed using silica gel 60-F254 plates. Melting points are re-
ported uncorrected. IR spectra were recorded as neat samples or
in KBr pellets. 1H and 13C NMR spectra were obtained on either
a 300- or 600-MHz instrument. Data are reported as s = singlet,
d = doublet, t= triplet, q= quartet, m = multiplet, br=broad;
coupling constants(s) in Hz, integration. Specific rotation mea-
surements are given in deg cm3 g-1 dm-1. Mass spectra and
high resolution mass spectra were performed by the analytical
division at Brock University.
(1S,2S,4R,5S,6S,7S)-5,6-(Isopropylidenedioxy)-3-(40-methyl-
phenylsulfonyl)-8-oxa-3-aza-tricyclo[5.1.0.0]octane (25a) and
(1S,2S,4R,5S,6S,7R)-5,6-(Isopropylidenedioxy)-3-(40-methylph-
enylsulfonyl)-8-oxa-3-aza-tricyclo[5.1.0.0]octane (25b). A solu-
tion of m-CPBA (10.5 g, 46.7 mmol) in 1,2-dichloroethane (150
mL) was dried over Na2SO4 and filtered into a flask containing
aziridine 18 (5.0 g, 15.6 mmol). The resulting solution was
heated to reflux until total consumption of starting material
(6 h). The reaction mixture was allowed to cool to room
temperature at which time m-chlorobenzoic acid crystallized
out as a white solid. The reaction mixture was filtered and
concentrated. The residue was taken up in EtOAc (350 mL) and
washed sequentially with NaHSO3 (2 ꢀ 100 mL), carbonate (2 ꢀ
100 mL), and brine (35 mL). The organic phase was dried over
Na2SO4, filtered, and concentrated to yield a 2.89:1 mixture of
epoxides 25a and 25b (5.035 g. 96%) as a slightly yellow solid.
The epoxide could be used without further purification or
enriched in favor of the major isomer by successive recrystal-
lizations form isopropanol. A small sample of the mixture
taken and the two epoxides were separated by flash column
chromatography (10% deactivated silica gel, hexanes/ethyl acet-
ate 7:1-4:1) to provide analytical samples of epoxide 25a and 25b.
Epoxide 25a. Rf 0.43 (hexanes/ethyl acetate, 2:1); mp 115-
116 °C (isopropanol); [R]21D -79.36 (c 1.0, CHCl3); IR (film) ν2
988, 2936, 1597, 1383, 1373, 1329, 1251, 1218, 1158, 1091, 1055
cm-1; 1H NMR (300 MHz, CDCl3) δ 7.90 (d, J = 8.3 Hz, 2H),
7.36 (d, J = 8.3 Hz, 2H), 4.4 (d, J = 6.2 Hz, 1H), 4.26 (d, J =
6.0 Hz, 1H), 3.53 (t, J = 3.7 Hz, 1H), 3.38 (dd, J = 6.8 Hz, J =
3.8 Hz, 1H), 3.13 (dd, J = 3.5 Hz, J = 0.9 Hz, 1H), 3.04 (dd, J =
6.8 Hz, J = 1.1 Hz, 1H), 2.46 (s, 3H), 1.46 (s, 3H), 1.36 (s, 3H);
13C NMR (75 MHz, CDCl3) δ 144.9, 134.5, 129.9, 128.0, 110.2,
70.8, 69.8, 50.1, 46.7, 37.3, 35.7, 27.4, 25.2, 21.7; HRMS-EI
calcd for C16H19NO5S (Mþ - 15) 322.0749, found 322.0744.
Anal. Calcd for C16H19NO5S: C, 56.96; H, 5.68 . Found: C,
56.83; H, 5.61
[R]22 -113.05 (c 0.5, CHCl3); Rf 0.30 (hexanes/ethyl acetate,
D
1
2:1); IR (film) ν 3491, 2988, 1163 cm-1; H NMR (300 MHz,
CDCl3) δ 7.78 (d, J = 8.1 Hz, 2H), 7.38 (d, J = 8.1 Hz, 2H), 6.91
(dd, J = 8.2 Hz, 1.8 Hz 1H), 6.83 (d, J = 1.5 Hz, 1H), 6.73 (d,
J = 7.9 Hz, 1H), 5.97 (s, 2H), 4.47 (d, J = 6.4 Hz, 1H), 4.22 (dd,
J = 6.1, 4.4 Hz, 1H), 3.98 (m, 1H), 3.40 (d, J = 6.4 Hz, 1H), 3.24
(m, 2H), 3.06 (d, J = 9.6 Hz, 1H), 2.47 (s, 3H), 1.49 (s, 3H), 1.32
(s, 3H) ppm; 13C NMR (75 MHz, CDCl3) δ 148.1, 147.5, 145.7,
134.2, 130.4, 128.1, 126.4, 116.2, 111.8, 110.3, 108.6, 101.5, 84.2,
83.8, 75.4, 70.1, 68.7, 42.3, 40.5, 31.1, 27.4, 25.2, 21.9 ppm; HRMS
(FAB Mþ) calcd for C25H25NO7S 484.1430, found 484.1428.
The free alcohol intermediate (0.8 g, crude) was dissolved in
20 mL of CH2Cl2, and triethylamine (0.484 mL, 3.48 mmol) was
added. The reaction flask was cooled to -78 °C, and tert-
butyldimethylsilytriflate (0.457 mL, 0.1.99 mmol) was added
dropwise to the stirring solution. After stirring for 30 min at
-78 °C, the reaction mixture was quenched with water (20 mL),
and the two phases separated. The aqueous phase was extracted
with CH2Cl2 (3 ꢀ 50 mL, and the combined organic solution was
washed sequentially with 5% citric acid (2 mL) and brine (2 mL)
before drying over sodium sulfate. The solvent was removed
under reduced pressure, and the residue was purified by flash
column chromatography (hexane/ethyl acetate, 9:1 to 2:1)
affording 27 (0.677 g, 77%) as a colorless oil; [R]24 þ57.7 (c
D
0.5, CHCl3); Rf 0.49 (hexanes/ethyl acetate, 2:1); IR (film) ν
2953, 2929, 2892, 2856, 1599,1490 cm-1; 1H NMR (300 MHz,
CDCl3) δ 7.83 (d, J = 8.1 Hz, 2H), 7.38 (d, J = 8.1 Hz, 2H), 6.94
(d, J = 8.1 Hz, 1H), 6.84 (s, 1H), 6.77 (d, J = 8.1 Hz, 1H), 5.99
(s, 2H), 4.45 (d, J = 5.1 Hz, 1H), 3.83 (m, 2H), 3.26 (m, 2H), 2.84
(d, J = 7.5 Hz), 2.47 (s, 3H), 1.52 (s, 3H), 1.35 (s, 3H), 0.87 (s,
9H), 0.11 (s, 6H) ppm; 13C NMR (75 MHz, CDCl3) δ 147.8,
147.3, 134.7, 129.8, 127.9, 126.1, 111.6, 109.7, 108.4, 101.3, 86.3,
83.5, 71.7, 43.2, 39.53, 34.58, 27.9, 25.8, 25.79, 25.7, 21.7, 18.12,
-4.4, -4.7 ppm; HRMS-EI calcd for C27H30NO7SSi 540.1481,
found 540.1487.
Epoxide 25b. Rf 0.43 (hexanes/ethyl acetate, 2:1); mp 179-
D
180 °C (isopropanol); [R]21 -62.82 (c 1.0, CHCl3); IR (film)
ν2985, 2929, 1602, 1384, 1366, 1324, 1245, 1222, 1163, 1153,
1041, 1001 cm-1; 1H NMR (600 MHz, CDCl3) δ 7.83 (d, J =
8.1 Hz, 2H), 7.39 (d, J = 8.1 Hz, 2H), 4.40 (d, J = 6.3 Hz, 1H),
4.31 (dd, J = 6.2 Hz, J = 2.3 Hz, 1H), 3.58 (dd, J = 3.9 Hz, J =
2.4 Hz, 1H), 3.44 (dd, J = 6.7 Hz, J = 2.0 Hz, 1H), 3.27 (d, J =
3.5 Hz, 1H), 3.18 (t, J = 6.8 Hz, 1H), 2.48 (s, 3H), 1.54 (s, 3H),
1.35 (s, 3H); 13C NMR (150 MHz, CDCl3) δ:145.3, 133.7, 130.0,
128.1, 111.1, 71.9, 69.9, 52.4, 25.0, 39.3, 38.6, 26.6, 25.9, 21.7;
HRMS-EI calcd for C16H19NO5S (Mþ - 15) 322.0749, found
322.0753. Anal. Calcd for C16H19NO5S: C, 56.96; H, 5.68.
Found: C, 56.23; H, 5.61
(1S,2R,3R,4R,5S,6R)-3,4-(Isopropylidenedioxy)-5-[(tert-butyl-
dimethylsilyl)oxy]-6-2-benzo[1,3]dioxol-5-ylethenyl-(40-methyl-
phenylsulfonyl)-7-azabicyclo[4.1.0]heptane (20). (A) Alkyne 27
(500 mg, 0.837 mmol) was taken up in 45 mL of MeOH, and
quinoline (34 mg, 0.168 mmol) added. Lindlar’s catalyst (35 mg,
0.335 mmol) was added. The reaction mixture was purged with
aspirator vacuum and flushed with H2 before being placed under
J. Org. Chem. Vol. 75, No. 9, 2010 3079

Collins et al.
JOCArticle
H2 using a balloon and stirred for 3 h. The reaction mixture was
filtered through a short plug a Celite, and the solvent was
removed under reduced pressure. The crude residue was purified
by flash column chromatography (hexanes/ethyl acetate, 4:1) to
give the title compound as a clear and colorless oil (480 mg,
(hexanes/ethyl acetate, 2:1); IR (film) ν 3268, 2929, 2887, 2857,
1598,1503, 1485 cm-1; 1H NMR (600 MHz, CDCl3) δ 7.43 (d, J
= 7 Hz, 2H), 7.13 (d, J = 7 Hz, 2H), 6.49 (s, 2H), 6.34 (d, J = 8
Hz, 1H), 5.95 (s, 1H), 5.86 (s, 1H), 5.76 (d, J = 8 Hz, 1H), 4.51 (d,
J = 7 Hz, 1H), 4.28 (m, 1H), 4.11 (m, 1H), 3.99 (m, 1H), 3.79 (m,
1H), 2.82 (m, 1H), 2.62 (dd, J = 11.1 Hz, J = 5.4 Hz, 1H), 2.40 (s,
3H), 1.43 (s, 3H), 1.33 (s, 3H), 0.89 (s, 9H), 0.11 (s, 3H), 0.07 (s,
3H) ppm; 13C NMR (150 MHz, CDCl3) δ 146.7, 145.9, 142.1,
138.9, 128.9, 128.6, 127.7, 126.8, 126.3, 126.2, 110.4, 109.2, 107.0,
79.0, 78.3, 70.3, 54.1, 42.5, 41.5, 38.9, 27.8, 26.3, 25.7, 25.3, 22.7,
21.5, 18.0, -5.0, -5.0 ppm; HRMS-EI calcd for C31H41NO7SSi:
599.2373, found 599.2370. Anal. Calcd for C31H41NO7SSi: C,
62.07; H, 6.89. Found: C, 62.16; H, 6.94.
N-[(1R,2aS,4aS,5S,5aS,12bR)-5-(tert-Butyl-dimethyl-silany-
loxy)-6-hydroxy-3,3-dimethyl-7-oxo-1,2a,4a,5,5a,6,7,12b-octa-
hydro-phenanthro[2,3-d][1,3]dioxol-1-yl]4-methyl-benzenesulfo-
namide (30). To a solution of olefin 21 (0.24 mg, 0.4 mmol) in
methylene chloride (10 mL) was added 4-methylmorpholine N-
oxide (96.7 mg, 0.8 mmol). The reaction mixture was allowed to
stir for 10 min before the introduction of a single crystal of
osmium tetroxide and two drops of water. The reaction mixture
was stirred until total consumption of starting material (10 h)
before being quenched with a saturated solution of sodium
bisulfite (6 mL). The two layers were separated, and the aqueous
phase was extracted with ethyl acetate (3 ꢀ 30 mL). The organic
phase was dried over sodium sulfate, filtered, and concentrated
in vacuo to provide hydroxyketone 30 as a white crystalline solid
(0.227 g, 89%) that was used without further purification; Rf
0.42 (hexanes/ethyl acetate, 1:1); mp >200 °C (hexanes/ethyl
acetate); IR (film) ν 3478, 3263, 2929, 2857, 1670, 1614, 1504,
1482, 1444, 1386, 1330, 1252, 1218, 1156, 1075, 1039 cm-1; 1H
NMR (600 MHz, CDCl3) δ 7.54 (d, J = 7.8 Hz, 2H), 7.49, (s,
1H), 7.18 (d, J = 7.8 Hz, 2H), 6.70 (s, 1H), 6.07 (s, 1H), 6.00 (s,
1H), 4.79 (d, J = 8.7 Hz, 1H), 4.71 (m, 2H), 4.19 (m, 1H), 4.08
(m, 1H), 3.74 (m, 2H), 3.08 (dd, J = 10.2 Hz, J = 1.8 Hz, 1H),
2.45 (m, 1H), 2.41 (s, 3H), 1.36 (s, 3H), 1.31 (s, 3H), 0.87 (s, 9H),
0.12 (s, 3H), 0.07 (s, 3H) ppm; 13C NMR (150 MHz, CDCl3) δ
196.6, 152.5, 147.9, 142.6, 140.5, 138.9, 129.1, 126.9, 124.7,
111.2, 109.6, 106.9, 102.1, 78.9, 78.7, 70.3, 65.9, 57.9, 49.4,
39.7, 27.9, 25.7, 21.5, 17.95, -5.1 ppm; HRMS-EI calcd for
C27H32NO9SSi (Mþ - 57) 574.1567, found 574.1572.
(3aS,3bR,10bR,11R,12S,12aS)-12-(tert-Butyl-dimethyl-silan-
yloxy)-2,2-dimethyl-5-oxo-4-(toluene-4-sulfonyl)-3a,3b,4,5,10b,
11,12,12a-octahydro-1,3,7,9-tetraoxa-4-aza-dicyclopenta[a,h]-
phenanthrene-11-carbaldehyde (22). To a 10 mL round-bot-
tomed flask was added hydroxyl ketone 30 (0.4 g, 0.63 mmol)
and 6 mL of a 1:1 mixture of ethanol/dioxane. The reaction flask
was cooled externally in an ice bath, and NaBH4 (24 mg,
0.63 mmol) was added in one portion. The reaction mixture
was removed from the bath and allowed to warm to room
temperature over 1 h and was then quenched with 1 N HCl
(4 mL) and separated. The aqueous phase was extracted with
CH2Cl2 (3ꢀ 20 mL), and the organic phase combined before
drying over sodium sulfate. The crude mixture was concentrated
in a 25 mL round-bottomed flash and taken up in dioxane
(8 mL). The reaction mixture was stirred while sodium periodate
(0.332, 1.5 mmol) was added. The flask was covered to exclude
light and H2O (15 drops) added. Stirring was continued until
total consumption of starting material (23 h) as monitored by
TLC. The reaction mixture was quenched with H2O (10 mL) and
separated. The aqueous phase was extracted with CH2Cl2 (3 ꢀ
50 mL), and the combined organic phases were dried over
sodium sulfate. Concentration provided hemiaminal (3aS,11R,
12S,12aS)-12-{[tert-butyl(dimethyl)silyl]oxy}-5-hydroxy-2,2-
dimethyl-4-[(4-methylphenyl)sulfonyl] 3a,3b,4,5,10b,11,12,12a-
octahydrobis[1,3]dioxolo[4,5-c:40,50-j]phenanthridine-11-carba-
ldehyde 32.
95%). (B) To a 1.0 M solution of BH3 THF complex (2.5 mL,
3
2.5 mmol) was added cyclohexene (0.484 mL, 4.77 mmol) at
0 °C. After 10 min a heavy precipitate was formed. The reaction
mixture was kept at 0 °C for 1 h before acetylene derivative 27
(0.356 mg, 0.596 mmol) in 4.5 mL of THF was added. The
reaction mixture was stirred at 0 °C until total consumption of
starting material (2 h, TLC) before being quenched with 1 mL of
HOAc. Then 60 mL of EtOAc was added, and the reaction
mixture was washed with saturated aq NaHCO3 (2 ꢀ 15 mL),
H2O (2 ꢀ 15 mL), and brine (10 mL) before drying over sodium
sulfate. The solvent was removed under reduced pressure, and
the residue was purified by flash column chromatography
(hexanes/ethyl acetate, 8:1) affording 0.271 g of 20 (76%);
[R]23 -26.14 (c 1.0, CHCl3; Rf 0.35 (hexanes/ethyl acetate,
D
1
4:1); IR (film) ν 2986, 2930, 2894, 2856, 1598,1489 cm-1; H
NMR (300 MHz, CDCl3) δ 7.78 (d, J = 8.1 Hz, 2H), 7.29 (d,
J = 8.1 Hz, 2H), 6.65 (m, 3H), 6.51 (d, J = 11.7 Hz, 1H), 5.97 (s,
2H), 5.54 (t, J = 11.3 Hz, 1H), 4.43 (d, J = 6, 1H), 3.85 (t, J =
6.3, 1H), 3.61 (t, J = 7.2 Hz), 3.18 (d, J = 6.6, 1H), 2.91 (m, 2H),
2.44 (s, 3H), 1.52 (s, 3H), 1.33 (s, 3H), 0.79 (s, 9H), 0.02 (s, 3H),
-0.04 (s, 3H) ppm; 13C NMR (150 MHz, CDCl3) δ 147.5, 146.6,
144.6, 134.7, 132.0, 129.8, 129.7, 128.5, 122.5, 109.35, 109.0,
108.1, 100.9, 83.2, 78.0, 72.6, 71.8, 43.7, 39.9, 39.5, 30.1, 27.8,
25.8, 25.79. 25.75, 25.72, 25.51, 23.7, 21.7, 18.1, -4.3, -4.7 ppm;
HRMS-EI calcd for C31H41NO7SSi: 599.2373, found 599.2376.
Anal. Calcd for C31H41NO7SSi: C, 62.28; H, 6.58. Found: C, 61.30;
H, 6.63. [Compound is a heavy oil, retaining residual solvent].
(1S,2R,3R,4R,5S,6R)-3,4-(Isopropylidenedioxy)-5-[(tert-butyl-
dimethylsilyl)oxy]-6-2-benzo[1,3]dioxol-5-ylethanyl-(40-methyl-
phenylsulfonyl)-7-azabicyclo[4.1.0]heptane (28). Alkyne 27
(100 mg, 0.168 mmol) was taken up in 10 mL of MeOH, and
Lindlar’s catalyst (35 mg, 0.34 mmol) was added. The reaction
mixture was purged with aspirator vacuum and flushed with H2
before being placed under H2 using a balloon and stirred for 24 h.
The reaction mixture was filtered through a short plug of Celite,
and the solvent was removed under reduced pressure. The crude
residue was purified by flash column chromatography (hexanes/
ethyl acetate, 4:1) to give the title compound as a clear and color-
less oil (95 mg, 94%); [R]23 -477.2 (c 1.8, CHCl3); Rf 0.35
D
(hexanes/ethyl acetate, 2:1); IR (film) ν 2986, 2954, 2929, 2891,
2857,1598,1504,1489 cm-1; 1H NMR (500 MHz, CDCl3) δ 7.87
(d, J = 7 Hz, 2H), 7.37 (d, J = 7 Hz, 2H), 6.70 (d, J = 6.5 Hz, 1H),
6.55 (s, 1H), 6.51 (d, J = 7 Hz, 1H), 5.93 (s, 2H), 4.41 (d, J = 5 Hz,
1H), 3.79 (t, J = 5 Hz, 1H), 3.43 (m, 1H), 3.18 (d, J = 6 Hz, 1H),
2.84 (m, 1H), 2.60 (m, 1H), 2.45 (s, 3H), 2.40 (m, 1H), 2.05 (m, 1H),
1.68 (s, 3H), 1.34 (s, 3H), 0.83 (s, 9H), 0.06 (s, 3H), 0.03 (s, 3H); 13
C
NMR (250 MHz, CDCl3) δ 146.6, 145.7, 144.8, 135.1, 134.9, 129.8,
128.0, 127.9, 121.2, 109.2, 108.9, 1081, 100.8, 78.6, 72.5, 71.9, 43.2,
39.9, 39.5, 32.9, 32.7, 27.8, 25.9, 25.8, 25.5, 21.7, 18.2, -4.0, -4.8;
HRMS-EI calcd for C31H43NO7SSi 601.2530, found 601.2534.
N-[(1R,2aS,4aS,5S,5aR,12bR)-5-(tert-Butyl-dimethyl-silany-
loxy)-3,3-dimethyl-1,2a,4a,5,5a,12b-hexahydro-phenanthro[2,3-d]-
[1,3]dioxol-1-yl]4-methyl-benzenesulfonamide (21). A flame-dried
25-mL flask was charged with olefin 20 (336 mg, 0.561 mmol) and
silica gel that had been activated by heating under vacuum at
120 °C overnight (1.5 g). The starting materials were suspended in
10 mL of freshly distilled methylene chloride, and the solvent was
removed under reduced pressure. The silica gel supporting the
absorbed reactants was heated externally at 120 °C under nitro-
gen atmosphere for 24 h, after which time the silica gel was loaded
onto a flash silica gel column and eluted with hexanes/
ethyl acetate, 8:1-5:1 to give 249 mg (74%) of olefin 21 as a
clear and colorless oil; [R]23 -123.7 (c 1.0, CHCl3); Rf 0.35
D
3080 J. Org. Chem. Vol. 75, No. 9, 2010

Collins et al.
JOCArticle
To a solution of hemiaminal 32 (394 mg, 0.62 mmol) in N,N-
dimethylformamide (3 mL) was added 2-iodoxybenzoic acid
(520 mg, 1.86 mmol). After total consumption of starting
material (by TLC), the reaction mixture was diluted with diethyl
ether (200 mL) and washed sequentially with saturated aqueous
sodium bisulfite (10 mL), sodium bicarbonate (3 ꢀ 10 mL), H2O
(10 ꢀ1 mL), and brine (10 mL). The organic phase was dried
over magnesium sulfate, filtered ,and concentrated. The final
product 22 was isolated by column chromatography (hexanes/
ethyl acetate, 4:1). Yield: 225 mg, 61%, white solid; Rf 0.31
(hexanes/ethyl acetate, 4:1); mp >200 °C, recrystallized from
bicarbonate solution (2 ꢀ 1 mL), dried over magnesium sulfate,
filtered, and concentrated. The crude reaction mixture was
passed through a short silica plug using hexane/ethyl acetate
1:1 as eluent and concentrated to provide methyl ester 35 that
was used without further purification. Yield: 38 mg, 83%, white
crystalline solid; Rf 0.45 (hexanes/ethyl acetate, 1:1); mp >200 °C
(hexane/ethyl acetate); [R]22 -25.6809 (c 0.75, CHCl3); IR
D
(KBr) ν 2986, 2953, 2931, 2896, 2858, 1739, 1692, 1620, 1598,
1505, 1485, 1361, 1289, 1264, 1173 cm-1; 1H NMR (300 MHz,
CDCl3) δ 8.30 (d, J = 8.4 Hz, 2H), 7.55 (s, 1H), 7.32 (d, J =
8.3 Hz, 2H), 6.58 (s, 1H), 6.02 (s, 2H), 5.78 (dd, J = 8.30 Hz, J =
5.4 Hz, 1H), 4.9 (dd, J = 12.5 Hz, J = 8.3 Hz, 1H), 4.78 (t,
J = 3.0 Hz, 1H), 4.24 (dd J = 5.36 Hz, J = 2.9 Hz, 1H), 3.79 (dd,
J = 12.4, J = 4.2 Hz, 1H), 3.56 (s, 3H), 3.40 (t, J = 3.7 Hz, 1H),
2.45 (s, 3H), 1.41 (s, 3H), 1.35 (s, 1H), 0.98 (s, 9H), 0.24 (s, 3H),
0.23 (s, 3H) ppm; 13C NMR (75 MHz, CDCl3) δ 169.4, 166.3,
152.8, 146.8, 143.7, 139.0, 138.2, 128.9, 128.8, 122.4, 109.8,
109.2, 103.5, 102.0, 72.9, 68.2, 65.2, 51.9, 48.1, 35.9, 27.5, 26.8,
25.7, 21.6, 18.0, -4.8, -4.9 ppm; HRMS-EI calcd for C28H32-
NO10SSi (Mþ - 57) 602.1516, found 602.1516.
hexanes/ethyl acetate 4:1; [R]21 þ 31.67 (c 0.5, CHCl3); IR
D
(film) ν 2929, 2857, 1725, 1689, 1619, 1505, 1484, 1386, 1361,
1287, 1255, 1220, 1172, 1077, 1036 cm-1; 1H NMR (600 MHz,
CDCl3) δ 9.49 (s, 1H), 8.3 (d, J = 8.2 Hz, 2H), 7.58 (s, 1H), 7.33
(d, J = 8.2 Hz, 2H), 7.28 (s, 1H), 6.55 (s, 1H), 6.04 (d, J = 5 Hz,
2H), 5.81 (dd, J = 8.4 Hz, J = 5.2 Hz, 1H), 4.79 (m, 1H), 4.50
(dd, J = 12.7 Hz, J = 8.4 Hz, 1H), 4.27 (dd, J = 5.2 Hz, J =
2.7 Hz, 1H), 3.83 (dd, J = 12.6, J = 4.0 Hz, 1H), 3.31 (m, 1H),
2.45 (s, 3H), 1.42 (s, 3H), 1.32 (s, 1H), 0.99 (s, 9H), 0.26 (s, 3H),
0.25 (s, 3H) ppm; 13C NMR (150 MHz, CDCl3) δ 196.2, 166.0,
153.0, 147.1, 143.9, 138.8, 137.0, 128.9, 128.8, 110.1, 109.4,
104.2, 102.2, 72.4, 66.6, 65.5, 55.6, 35.4, 31.0, 27.9, 26.9, 25.7,
22.7, 21.7, 18.1, 14.2, -4.7, -4.9 ppm; HRMS-EI calcd for
C30H36NO9SSi (Mþ - 15) 614.1879, found 614.1870. Anal. Calcd
for C31H39NO9SSi: C, 59.12; H, 6.24. Found: C, 59.31; H, 6.29.
(3aS,3bR,10bR,11R,12S,12aS)-12-(tert-Butyl-dimethyl-silan-
yloxy)-2,2-dimethyl-5-oxo-4-(toluene-4-sulfonyl)-3a,3b,4,5,10b,
11,12,12a-octahydro-1,3,7,9-tetraoxa-4-aza-dicyclopenta[a,h]-
phenanthrene-11-carboxylic Acid (34). To a solution of aldehyde
22 (144 mg, 0.229 mmol) in dry methylene chloride (5 mL) was
added sodium phosphate dibasic (81 mg, 0.57 mmol). The
suspension was stirred while 3-chloroperbenzoic acid (130 mg,
0.57 mmol) was added. The reaction flask was sealed and heated
at 40 °C overnight. The reaction mixture was diluted with
methylene chloride (80 mL) and washed sequentially with
saturated aqueous sodium bisulfite (10 mL) and sodium bicar-
bonate (10 mL) and dried over sodium sulfate. The organic
phase was filtered and concentrated in vacuo to provide car-
boxylic acid 34 as a white crystalline solid (0.125 g, 85%) that
was used without further purification; Rf 0.1 (hexanes/ethyl
(3aS,3bR,10bR,11R,12S,12aS)-12-(tert-Butyl-dimethyl-silan-
yloxy)-2,2-dimethyl-5-oxo-3a,3b,4,5,10b,11,12,12a-octahydro-
1,3,7,9-tetraoxa-4-aza dicyclopenta[a,h]phenanthrene-11-car-
boxylic Acid Methyl Ester (38). To a solution of 35 (52 mg, 0.079
mmol) in dry THF (1 mL) at -50 °C was added a 0.5 M solution
of Na/naphthalene in DME until a green color persisted and
total consumption of starting material was observed (by TLC).
The solution was stirred for 10 min before the reaction mixture
was quenched with saturated aqueous ammonium chloride
solution (1 mL), warmed to room temperature, and extracted
with CH2Cl2 (6 ꢀ 15 mL). The combined organic phase was
dried over sodium sulfate, filtered, and concentrated. The final
product was isolated by column chromatography (hexanes/
ethyl acetate, 5:1 to 2:1). Yield: 23 mg, 58%, clear oil; Rf 0.28
(hexanes/ethyl acetate, 1:1); [R]22D -14.51 (c 0.50, CHCl3); IR
(film) ν3320, 2952, 2930, 2895, 2857, 1743, 1669, 1619, 1504,
1
1484, 14601385, 1369, 1321, 1288, 1260, 1222 cm-1; H NMR
(600 MHz, CDCl3) δ 7.62 (s, 1H), 6.56 (s, 1H), 6.02 (s, 2H), 5.96
(s, 1H), 4.86 (t, J = 2.6, 1H), 4.41 (dd, J = 13.6 Hz,
J = 8.2 Hz, 1H), 4.18 (dd, J = 8.25 Hz, J = 4.8 Hz, 1H), 4.11
(m, 1H), 3.66 (s, 3H), 3.40 (dd, J = 13.6 Hz, J = 3.7 Hz, 1H),
3.33 (m, 1H), 2.06 (s, 1H), 1.40 (s, 3H), 1.37 (s, 3H), 0.92 (s, 9H),
0.21 (s, 3H), 0.20 (s, 3H) ppm; 13C NMR (150 MHz, CDCl3) δ
169.6, 165.4, 151.4, 146.6, 135.4, 122.6, 110.5, 108.6, 103.3,
101.7, 69.2, 53.1, 51.9, 45.9, 33.4, 27.6, 26.5, 25.7, 17.9, -4.9,
-5.0 ppm; HRMS-EI calcd for C25H35NO8Si (Mþ) 505.2132,
found 505.2131.
acetate, 1:1); mp >200 °C (chloroform/ether); [R]22 -35.09
D
(c 1.25, CHCl3); IR (KBr) ν 3246, 2930, 2891, 2857, 1710, 1688,
1619, 1505, 1484, 1361, 1240, 1220, 1172, 1078, 1033 cm-1; 1H
NMR (300 MHz, CDCl3) δ 8.29 (d, J = 8.3 Hz, 2H), 7.53 (s,
1H), 7.32 (d, J = 8.3 Hz, 2H), 7.28 (s, 1H), 6.56 (s, 1H), 6.02 (d,
J = 3 Hz, 2H), 5.77 (dd, J = 8.30 Hz, J = 5.3 Hz, 1H), 4.85 (dd,
J = 12.5 Hz, J = 8.4 Hz, 1H)), 4.84 (t, J = 4.7 Hz, 1H), 4.22 (dd
J = 5.22, J = 2.8 Hz, 1H), 3.76 (dd, J = 12.4 Hz, J = 4.1 Hz,
1H), 3.38 (t, J = 3.5 Hz, 1H), 2.45 (s, 3H), 1.40 (s, 3H), 1.27 (s,
1H), 0.96 (s, 9H), 0.21 (s, 6H) ppm; 13C NMR (150 MHz,
CDCl3) δ 174.3, 166.2, 152.8, 146.9, 143.8, 138.9, 137.7, 129.0,
128.8, 122.4, 109.8, 109.2, 103.4, 102.1, 72.8, 68.2, 64.9, 48.0,
35.5, 27.4, 26.9, 25.7, 21.7, 18.0, -4.9, -5.0 ppm; HRMS-EI
calcd for C27H30NO10SSi (Mþ - 57) 588.1359, found 588.1354.
Anal. Calcd for C31H39NO10SSi: C, 57.65; H, 6.09. Found: C,
58.01; H, 6.37.
(1R,2S,3R,4S,4aR,11bR)-2,3,4-Trihydroxy-6-oxo-1,2,3,4,4a,
5,6,11b-octahydro-[1,3]dioxolo[4,5-j]phenanthridine-1-carboxylic
Acid Methyl Ester (39). To a solution of the detosylated methyl
ester 38 (23 mg, 0.046 mmol) in methanol (2 mL) was added 3%
HCl in methanol (0.5 mL). The reaction mixture was stirred
until total consumption of starting material (3 days). The
solvent was removed under reduced pressure, and the residue
was purified by flash column chromatography using a 30:1 to
20:1 gradient of methylene chloride/methanol as eluent to pro-
vide methyl ester 39 (11 mg, 69%) as a white crystalline solid; mp
>200 °C (methylene chloride/methanol); Rf 0.06 (methylene
(3aS,3bR,10bR,11R,12S,12aS)-12-(tert-Butyl-dimethyl-silan-
yloxy)-2,2-dimethyl-5-oxo-4-(toluene-4-sulfonyl)-3a,3b,4,5,10b,
11,12,12a-octahydro-1,3,7,9-tetraoxa-4-aza-dicyclopenta[a,h]-
phenanthrene-11-carboxylic Acid Methyl Ester (35). To a solu-
tion of carboxylic acid 34 (45 mg, 0.069 mmol) in diethyl ether
(3 mL) was added freshly prepared diazomethane solution in
diethyl ether until the persistence of yellow color and total
consumption of starting material (by TLC). The reaction mix-
ture was quenched with one drop of acetic acid followed by
saturated sodium bicarbonate solution (1 mL), diluted with
diethyl ether (30 mL), and washed with saturated sodium
chloride/methanol, 20:1); [R]22 þ 24.53 (c 0.25,MeOH); IR
D
(KBr) ν3311, 2913, 1732, 1648, 1609, 1497, 1462, 1349, 1259,
1037 cm-1; 1H NMR (300 MHz, MeOD) δ 7.33 (s, 1H), 6.59 (s,
1H), 5.93 (d, J = 3.7, 2H), 4.50 (t, J = 3.12, 1H), 4.21 (dd, J =
13.1 Hz, J = 10.1 Hz, 1H), 3.86 (m, 1H), 3.79, (dd, J = 10.1, J =
3.0, 1H), 3.51 (s, 3H), 3.39 (m, 1H), 3.29 (dd, J = 13.1, J = 4.1,
1H) ppm; 13C NMR (75 MHz, MeOD) δ 170.8, 166.4, 151.7,
146.4, 137.3, 121.7, 106.9, 103.7, 101.8, 72.2, 71.9, 70.9, 51.4,
50.6, 44.8, 35.4 ppm; HRMS-FAB (m/z) (M þ H)þ calcd for
C16H17NO8 352.0947, found 352.0941.
J. Org. Chem. Vol. 75, No. 9, 2010 3081

Collins et al.
JOCArticle
(1R,2S,3R,4S,4aR,11bR)-2,3,4-Trihydroxy-6-oxo-1,2,3,4,4a,
5,6,11b-octahydro-[1,3]dioxolo[4,5-j]phenanthridine-1-carboxylic
Acid (40). To a solution of 39 (6 mg, 0.017 mmol) in methanol
(0.5 mL) was added LiOH (1 mg, 1.5 mmol). The reaction
mixture was heated at 45 °C and stirred until total consumption
of starting material (2 days) as monitored by TLC. The reaction
mixture was made slightly acidic with the addition of HCl
(5 drops, 1 M) and concentrated to provide acid 40 (5 mg,
95%) as a white crystalline solid; mp >200 °C (methanol); Rf
0.06 (methylene chloride:methanol, 4:1); IR (KBr) ν 3412, 2920,
2115, 1641, 1505, 1471, 1409, 1462, 1363, 1267 cm-1; 1H NMR
(300 MHz, MeOD) δ 7.41 (s, 1H), 6.72 (s, 1H), 6.02 (d, J = 3.7,
2H), 4.64 (t, J = 3.12, 1H), 4.35 (dd, J = 13.1 Hz, J = 10.1 Hz,
1H), 3.99 (m, 1H), 3.89, (dd, J = 10.1, J = 3.0, 1H), 3.45 (m,
1H), 3.38 (m, 1H) ppm; 13C NMR (75 MHz, MeOD) δ 172.1,
166.4, 151.7, 146.4, 137.6, 121.7, 106.8, 103.8, 101.8, 72.4, 71.9,
71.1, 51.34, 45.03, 35.4 ppm.
(3aS,3bR,10bR,11S,12S,12aS)-12-(tert-Butyl-dimethyl-silany-
loxy)-11-hydroxymethyl-2,2-dimethyl-4-(toluene-4-sulfonyl)-3b,
4,10b,11,12,12a-hexahydro-3aH-1,3,7,9-tetraoxa-4-aza-dicyclo-
penta[a,h]phenanthren-5-one (41). To a solution of aldehyde 22
(175 mg, 0.278 mmol) in EtOH/dioxane (1:1, 5 mL) at 0 °C was
added NaBH4 (3 mg, 0.08 mmol). The reaction mixture was
allowed to warm to room temperature over 1.5 h before being
quenched with a solution of saturated NH4Cl (1 mL). The
EtOH/dioxane mixture was removed under reduced pressure,
and the aqueous residue was extracted with CH2Cl2 (3 ꢀ 25 mL).
The organic phases were combined, dried over sodium sulfate,
filtered, and concentrated to provide alcohol 41, which was used
without further purification. Yield: 150 mg, 85%, clear oil; Rf
0.44 (hexanes/ethyl acetate, 1:1); [R]22D -47.72 (c 1.50, CHCl3);
IR (film) v 3547, 2986, 2932, 2586, 1692, 1616, 1594, 1508, 1481,
1360 cm-1; 1H NMR (300 MHz, CDCl3) δ 8.28 (d, J = 8.3 Hz,
2H), 7.54 (s, 1H), 7.30 (d, J = 8.2 Hz, 2H), 6.77 (s, 1H), 6.04 (d,
J = 1.6 Hz, 2H), 5.65 (dd, J = 8.8 Hz, J = 5.6 Hz, 1H), 4.57 (d,
J = 1.8 Hz, 1H), 4.32 (d, J = 4.6 Hz, 1H), 4.16 (dd J = 12.8, J =
8.9 Hz, 1H), 3.78 (m 2H), 3.38 (dd, J = 11.3 Hz, J = 3.6 Hz, 1H),
2.55 (bs, 1H), 2.43 (s, 3H), 1.96 (bs, 1H), 1.43 (s, 3H), 1.35 (s,
3H), 0.96 (s, 9H), 0.20 (s, 6H) ppm; 13C NMR (75 MHz, CDCl3)
δ 166.4, 153.1, 147.1, 143.7, 138.9, 137.0, 129.0, 128.7, 123.2,
109.1, 108.7, 104.9, 102.1, 73.1, 67.3, 64.8, 60.0, 46.9, 37.4, 28.1,
26.3, 25.8, 21.6, 18.0, -4.8, -4.9 ppm; HRMS-EI calcd for
C31H41NO9SSi (Mþ - 15) 616.2032, found 616.2032.
138.8, 136.2, 129.1, 128.7, 123.2, 108.9, 108.8, 105.0, 102.2, 78.4,
73.0, 66.3, 64.4, 60.8, 44.0, 37.0, 28.3, 26.2, 25.8, 25.78, 25.75, 25.6,
21.6, 20.8, 18.1, -4.8, -5.0; HRMS-EI calcd for C32H40NO10SSi
(Mþ - 15) 658.2142, found 658.2152
((3aS,3bR,10bR,11S,12S,12aR)-12-Hydroxy-2,2-dimethyl-5-
oxo-3a,3b,4,5,10b,11,12,12a-octahydrobis[1,3]dioxolo[4,5-c:40,50-j]-
phenanthridin-11-yl)methyl Acetate (44). To a solution of 42
(137 mg, 0.203 mmol) in dry DME (5 mL) at -78 °C was added a
0.5 M solution of Na/naphthalene in DME until a green color
persisted and total consumption of starting material was ob-
served (by TLC). The solution was stirred for 10 min and then
quenched with saturated aqueous ammonium chloride solution
(2 mL). The reaction was warmed to room temperature, con-
centrated to remove DME, and extracted with CH2Cl2 (3 ꢀ
40 mL). The combined organic phase was dried over sodium
sulfate, filtered, and concentrated. The resulting crude acetate
was taken up in THF (2.5 mL) and cooled to 0 °C. TBAF
(0.1 mL, 1 M in THF) was added dropwise over 2 min. The
reaction mixture was stirred until total consumption of starting
material was observed (TLC) before the stirring bar was re-
moved, silica (200 mg) was added, and the mixture concentrated
to dryness. The final product was isolated by column chromato-
graphy using 1:1 mixture of hexanes/ethyl acetate as eluent.
Yield: 61 mg, 74%, white solid; mp >200 °C (ethyl acetate/
hexanes); Rf 0.059 (hexanes/ethyl acetate, 1:1); [R]22 -38.301
D
(c 1.35, DMSO); IR (film) ν3303, 2982, 2922, 2901, 2853, 1734,
1655, 1652, 1612, 1483, 1459, 1364, 1246, 1235, 1215; 1H NMR
(300 MHz, DMSO) δ 7.76 (s, 1H), 7.35 (s, 1H), 7.03 (s, 1H) 6.09
(d, J = 1.8, 2H), 5.48 (d, J = 4.2, 1H), 4.35, (s, 1H), 4.24 (d, J =
5.3, 1H), 4.19-4.10 (m, 3H), 3.46 (dd, J = 14.0 Hz, J = 8.2 Hz,
1H), 3.21 (dd, J = 13.9 Hz, J = 3.8 Hz, 1H), 2.80 (bs, 1H), 2.02
(s, 1H), 1.39 (s, 3H), 1.31 (s, 3H); 13C NMR (75 MHz, DMSO) δ
170.9, 163.9, 151.3, 146.7, 134.5, 124.2, 108.9, 107.6, 105.4, 102.2,
77.9, 77.2, 65.3, 61.2, 53.5, 34.7, 28.3, 26.4, 21.2; HRMS-EI calcd
for C20H23NO8 (Mþ) 405.1424, found 405.1431
((1S,2S,3R,4S,4aR,11bR)-2,3,4-Trihydroxy-6-oxo-1,2,3,4,4a,
5,6,11b-octahydro-[1,3]dioxolo[4,5-j]phenanthridin-1-yl)methyl
Acetate (46). To a solution of acetate 44 (21 mg, 0.052 mmol) in
MeOH (1 mL) was added an HCl solution (3% in MeOH, 3 mL).
The reaction mixture was stirred until total consumption of
starting material as monitored by TLC (3 h) before being
quenched to basic pH with saturated sodium bicarbonate solu-
tion. The crude reaction mixture was concentrated to dryness.
The final product was isolated by column chromatography
(methylene chloride/methanol, 5:1). Yield: 6 mg, 45%, white
solid; mp >200 °C (methylene chloride/methanol); Rf 0.41
(methlene chloride/methanol, 5:1); [R]22D 97.32 (c 0.3, DMSO);
1H NMR (600 MHz, DMSO) δ 7.36 (s, 1H), 7.01 (s, 1H), 6.76, (s,
1H), 6.10, (s, 2H), 5.14, (bs, 3H), 4.38 (t, J = 10.7 Hz, 1H),
4.15-4.10 (m, 2H), 3.84 (s, 1H), 3.70 (dd J = 9.8 Hz, J = 2.9 Hz,
1H), 3.50 (dd J = 13.2 Hz, J = 9.9 Hz, 1H), 3.27 (dd J = 13.3 Hz,
J = 4.0 Hz, 1H), 2.69 (bs, 1H), 2.03 (s, 3H) ppm; 13C NMR (150
MHz, DMSO) δ 171.0, 164.1, 151.3, 146.6, 135.3, 123.8, 107.5,
105.5, 102.2, 73.1, 71.3, 69.1, 61.9, 51.6, 36.9, 21.3 ppm; HRMS-
FAB calcd for C17H20NO8 (M þ 1) 366.1082, found 366.1088.
(1S,2S,3R,4S,4aR,11bR)-2,3,4-Trihydroxy-1-(hydroxymethyl)-
1,2,3,4,4a,5-hexahydro-[1,3]dioxolo[4,5-j]phenanthridin-6(11bH)-
one (45). To a solution of acetate 44 (25 mg, 0.062 mmol) at 0 °C,
in MeOH (5 mL) were added K2CO3 (40 mg, 0.62 mmol) and
H2O (1 mL). The suspension was stirred until total consumption
of starting material (TLC) before being quenched with HCl
(4 drops, 6 N). The reaction mixture was allowed to warm to
room temperature and stir (4 h). The pH of the reaction was
made basic with the addition of saturated sodium bicarbonate
solution, and the methanol was removed under reduced pres-
sure. The resulting aqueous phase was concentrated overnight
on a freeze-dryer. The salts were triturated with MeOH (5 ꢀ
5 mL), and the MeOH washes were collected and concentrated.
Acetic Acid (3aS,3bR,10bR,11S,12S,12aS)-12-(tert-Butyl-di-
methyl-silanyloxy)-2,2-dimethyl-5-oxo-4-(toluene-4-sulfonyl)-
3a,3b,4,5,10b,11,12,12a-octahydro-1,3,7,9-tetraoxa-4-aza-dicyclo-
penta[a,h]phenanthren-11-yl Methyl Ester (42). To a solution of
41 (150 mg, 0.237 mmol) in dry CH2Cl2 (10 mL) was added
DMAP (1.5 mg, 0.012 mmol), followed by pyridine (0.1 mL,
1.187 mmol). Ac2O (45 μL, 0.475 mmol) was added, and the
reaction mixture was stirred for 1 h before being quenched with
saturated sodium bicarbonate (5 mL), diluted with Et2O (75 mL),
and separated. The aqueous layer was extracted with Et2O (2 ꢀ
75 mL), and the combined organic phases were washed with H2O
(10mL) and brine (10mL), dried over magnesium sulfate, filtered,
and concentrated. The final product was isolated by column
chromatography using 5:1 mixture of hexanes/ethyl acetate as
eluent. Yield: 128 mg, 81%, clear oil; Rf 0.51 (hexanes/ethyl
acetate, 1:1); [R]22 -41.081 (c 3.0, CHCl3); IR (film) ν2988,
D
2952, 2930, 2858, 1742, 1694, 1619, 1598, 1505, 1485, 1395, 1362,
1254; 1H NMR (600 MHz, CDCl3) δ 8.29 (d, J = 8.3 Hz, 2H),
7.54 (s, 1H), 7.31 (d, J = 8.2 Hz, 2H), 6.84 (s, 1H), 6.03 (d, J =
12.6 Hz, 2H), 5.62 (dd, J = 8.7 Hz, J = 5.6 Hz, 1H), 4.50 (s, 1H),
4.31 (d, J = 5.3 Hz, 1H), 4.18 (t, J = 11.1 Hz, 1H), 3.97 (dd, J =
13.0 Hz, J = 8.8 Hz, 1H), 3.85 (dd, J = 11.0 Hz, J = 3.6 Hz, 1H),
3.80 (dd, J = 13.0, J = 4.2, 1H), 2.7 (d, J = 5.2, 1H), 2.44 (s, 3H),
2.03 (s, 3H), 1.42 (s, 3H), 1.36 (s, 3H), 0.96 (s, 9H), 0.19 (s, 1H); 13
C
NMR (150 MHz, CDCl3) δ 170.7, 166.2, 153.2, 147.3, 143.8,
3082 J. Org. Chem. Vol. 75, No. 9, 2010

Collins et al.
JOCArticle
The final product was isolated by column chromatography
(methylene chloride/methanol, 5:1). Yield: 15 mg, 75%, white
solid; mp >200 °C (methylene chloride/methanol); Rf 0.20
(methlene chloride/methanol, 5:1); [R]22D 90.91 (c 0.25, DMSO);
IR (film) ν3361, 2916, 1646, 1608, 1503, 1460, 1385, 1361, 1252;
1H NMR (600 MHz, DMSO) δ 7.34 (s, 1H), 6.97 (s, 1H), 6.66, (s,
1H), 6.09, (d, J = 0.78, 2H), 5.04-4.97, (m, 3H), 4.47 (dd J =
6.6 Hz, J = 3.8 Hz, 1H), 4.19 (s, 1H), 3.89 (q, J = 7.86 Hz, 1H),
3.82 (s, 1H), 3.69-3.64 (m, 1H), 3.42 (dd J = 13.2 Hz, J = 9.9
Hz, 1H), 3.39-3.32 (m, 1H), 3.15, (dd J = 13.3 Hz, J = 4.5 Hz,
1H), 2.41 (s, 1H) ppm; 13C NMR (150 MHz, DMSO) δ 164.2,
151.2, 146.3, 136.3, 123.7, 107.4, 105.6, 102.1, 73.3, 71.6, 69.7,
57.8, 51.8, 44.4, 37.3 ppm; HRMS-FAB calcd for C15H18NO7
(M þ 1) 324.1085, found 324.1084.
column chromatography (hexanes/ethyl acetate, gradient 2:1-
1:1). Yield: 13.6 mg, 64%, slight yellow oil; Rf 0.041 (hexanes/
ethyl acetate, 2:1); [R]22D þ 40.90 (c 0.50, CHCl3); IR (film) v IR
(film) v 3550, 2920, 1642, 1516, 1453 cm-1; 1H NMR (600 MHz,
CDCl3) δ 7.63 (s, 1H), 7.24 (d, J = 8.6 Hz, 2H), 6.82 (d, J = 8.6
Hz, 2H), 6.75 (s, 1H), 6.03, (s, 2H), 5.21 (d, J = 15.8 Hz, 1H),
4.90 (d, J = 15.5 Hz, 1H), 4.39 (dd, J = 7.6, J = 6.2 Hz, 1H),
4.23 (m, 1H), 4.12 (t, J = 5.61 Hz, 1H), 3.78 (s, 3H), 3.71 (dd,
J = 13.4, J = 7.9 Hz, 1H), 3.19 (td, J = 12.4, 5.0 Hz, 1H),
2.36-2.28 (m, 2H), 2.01 (qd, J = 13.6, 11.9, 4.9 Hz, 1H), 1.387
(s, 3H), 1.34 (s, 3H) ppm; 13C NMR (150 MHz, CDCl3) δ
165.2,158.4, 151.1, 146.8, 135.4, 131.8, 128.2, 123.1, 113.7, 109.5,
108.6, 104.2, 101.6, 78.1, 75.9, 66.6, 61.6, 61.9, 55.3, 46.3, 32.3,
21.0, 28.0, 26.1 ppm; HRMS-EI calcd for C25H27NO7 (Mþ)
453.1788, found 453.1787.
(3aS,3bR,10bR,12S,12aS)-12-(tert-Butyldimethylsilyloxy)-
2,2-dimethyl-3b,4,10b,11,12,12a-hexahydrobis[1,3]dioxolo[4,5-c:
40,50-j]phenanthridin-5(3aH)-one (48). To a solution of aldehyde
22 (192 mg, 0.305 mmol) in toluene (10 mL) was added RhCl-
(PPh3)3 (424 mg, 0.458 mmol). The reaction vessel was sealed,
lowered into a preheated oil bath (130 °C), and stirred until total
consumption of starting material as monitored by TLC (7.5 h).
The crude reaction mixture was filtered through a silica plug
using a mixture of 2:1 hexanes/ethyl acetate as eluent and
allowed to stand overnight. The resulting yellow crystals were
removed by filtration, and the crude reaction mixture was
concentrated under reduced pressure and dried under vacuum.
The crude was taken up in DME (8 mL) and cooled to -60 °C.
To the acetonide solution was added a 0.5 M solution of Na/
naphthalene in DME until a green color persisted and total
consumption of starting material was observed (by TLC). The
solution was stirred for 10 min before the reaction mixture was
quenched with saturated aqueous ammonium chloride solution
(3 mL), warmed to room temperature, concentrated to remove
DME, and extracted with CH2Cl2 (3 ꢀ 50 mL). The combined
organic phase was dried over sodium sulfate, filtered, and
concentrated. The final product was isolated by column chro-
matography using 3:1 mixture of hexanes/ethyl acetate as eluent.
Yield: 101 mg, 74%, clear and colorless oil; Rf 0.49 (hexanes/
4-(4-Methoxybenzyl)-2,2-dimethyl-3b,4,10b,12a-tetrahydro-
3aH-1,3,7,9-tetraoxa-4-aza-dicyclopenta[a,h]phenanthren-5-one
(50). To a solution of alcohol 49 (15 mg, 0.033 mmol) in THF
(1 mL) at 0 °C was added a spatula tip of NaH (60% dispersion
in mineral oil). The reaction mixture was stirred at 0 °C for
10 min before being allowed to warm to rt and stir for 45 min.
The reaction was cooled externally to 0 °C again before CS2
(12 μL, 0.198 mmol) was added. After stirring for 1 h at 0 °C MeI
(25 μL, 0.397 mmol) was added, and the reaction was allowed to
warm to rt slowly over 5 h before being quenched with satd
NH4Cl (2 mL). The reaction mixture was concentrated to
remove THF, the aq residue was extracted with EtOAc (3 ꢀ
30 mL), and the organic phases combined and dried over sodium
sulfate. Following filtration, the EtOAc was removed under
reduced pressure, and the residue was taken up in o-zylene
(2 mL) and heated at reflux for 21 h. The reaction mixture was
concentrated under reduced pressure at 50 °C, and the crude
residue was loaded onto silica (100 mg). The final product was
isolated by flash column chromatography (hexanes/ethyl acet-
ate, 4:1). Yield: 5 mg, 35%, white solid; mp 172-174 °C (ethyl
acetate/hexanes); Rf 0.51 (hexanes/ethyl acetate, 1:1); [R]22
þ
D
37.48 (c 0.20, CHCl3); IR (film) v 2920, 1647, 1511, 1451 cm-1
;
1H NMR (600 MHz, CDCl3) δ 7.67 (s, 1H), 7.27 (d, J = 8.6 Hz,
2H), 6.92 (s, 1H), 6.84 (d, J = 8.6 Hz, 2H), 6.34 (d, J = 10.2 Hz,
1H), 6.11 (dt, J = 10.0 Hz, J = 3.1 Hz, 1H), 6.05 (s, 2H), 5.43 (d,
J = 15.6 Hz, 1H), 4.98 (d, J = 15.5 Hz, 1H), 4.64-4.61 (m, 1H),
4.39 (dd J = 9.3, J = 7.1 Hz, 1H), 3.80 (s, 3H), 3.66 (dd, J =
11.9, J = 9.3 Hz, 1H), 3.49 (d, J = 12.1, 1H), 1.38 (s, 3H), 1.35
(s, 3H) ppm; 13C NMR (150 MHz, CDCl3) δ 165.5, 158.3, 151.1,
146.9, 133.6, 132.6, 128.2, 127.9, 126.1, 123.7, 113.7, 109.3, 109.2,
103.8, 101.7, 74.8, 71.9, 60.8, 55.3, 45.8, 38.6, 27.6, 25.3 ppm;
HRMS-EI calcd for C25H25NO6 (Mþ) 435.1682, found 435.1683
7-Deoxy-trans-dihydrolycoricidine (7). To a solution of acet-
onide 48 (13 mg, 0.29 mmol) in MeOH (1 mL) was added a 10%
solution of HCl in MeOH (10 mL). The reaction mixture was
stirred until total consumption of starting material as monitored
by TLC (3 days). The final product was isolated by flash column
chromatography (chloroform/methanol, gradient 7:1-5:1).
Yield: 6.1 mg, 71%, white solid; mp >200 °C (MeOH); Rf
ethyl acetate, 1:1); [R]22 -20.929 (c 1.5, CHCl3); IR (film) ν
D
3360, 2952, 2929, 2894, 2857, 1670, 1615, 1505, 1482, 1459, 1384,
1
1345, 1270, 1256, 1243, 1219; H NMR (600 MHz, CDCl3) δ
7.59 (s, 1H), 6.77 (s, 1H), 6.28 (s, 1H) 6.03 (d, J = 5.28, 2H), 4.42
(d, J = 2.10, 1H), 4.18, (dd, J = 8.3 Hz, J = 4.8 Hz, 1H), 4.11
(m, 1H), 3.43 (dd, J = 13.2 Hz, J = 8.6 Hz, 1H), 3.12 (t, J = 13.5
Hz, 1H), 2.26 (d, J = 13.6 Hz, 1H), 1.77 (t, J = 13.9 Hz, 1H),
1.46 (s, 3H), 1.41 (s, 3H), 0.91 (s, 9H), 0.15 (s, 3H), 0.14 (s, 3H);
13C NMR (150 MHz, CDCl3) δ 165.7, 151.4, 146.7, 136.5, 122.9,
109.9, 108.4, 104.3, 101.7, 77.7, 66.9, 57.9, 31.9, 31.6, 28.3, 26.5,
25.7, 25.6, 21.1, 17.9, -4.8, -4.9 ppm; HRMS-EI calcd for
C23H33NO6Si (Mþ) 447.2077, found 447.2083
(3aS,3bR,10bR,12S,12aR)-12-Hydroxy-4-(4-methoxybenzyl)-
2,2-dimethyl-3b,4,10b,11,12,12a-hexahydro-3aH-1,3,7,9-tetraoxa-
4-aza-dicyclopenta[a,h]phenanthren-5-one (49). To a solution of
acetonide 48 (21 mg, 0.047 mmol) in DMF (0.24 mL) at 0 °C was
added NaH (spatula tip, 60% dispersion in mineral oil). The
reaction mixture was stirred at 0 °C for 10 min and then at rt for
20 min. The reaction mixture was cooled in ice again before
p-methoxy benzylbromide (11 μL, 0.07 mmol) was added, and
then the mixture was allowed to warm to rt over 2 h. The mixture
was taken up in Et2O (5 mL), quenched with H2O (2 mL),
transferred to a separatory funne,l and diluted further with Et2O
(50 mL). The ether layer was washed with H2O (6 ꢀ 0.5 mL) and
brine (1 ꢀ 1 mL), dried over magnesium sulfate, flitered, and
concentrated under reduced pressure. The crude residue was
taken up in THF (1 mL) and cooled to 0 °C. TBAF (56 μL,
0.056 mmol, 1 M in THF) was added, and the reaction mixture
was stirred for 20 min. Silica (0.2 g) added and the mixture
concentrated to dryness. The final product was isolated by flash
0.25 (methylene chloride/methanol, 5:1); [R]22 28.6 (c 0.25,
D
DMSO); IR (KBr) v 3559, 3488, 3450, 3429, 1671, 1471, 1263
1
cm-1; H NMR (600 MHz, DMSO-d6) δ 7.30 (s, 1H), 6.95 (s,
1H), 6.94 (s, 1H), 6.08 (s, 2H), 4.99 (d, J = 3.4 Hz, 1H), 4.96 (d,
J = 5.9 Hz, 1H), 4.84 (d, J = 3.2 Hz, 1H), 3.89, (br s, 1H), 3.72
(br s, 2H), 3.30 (d, J = 12.3 Hz, 1H), 2.89 (td, J = 12.4, J = 3.6
Hz, 1H), 2.15 (dt, J = 13.0, J = 3.0 Hz, 1H), 1.65 (td, J = 12.9,
J = 2.2 Hz, 1H) ppm; 13C NMR (150 MHz, DMSO-d6) δ 164.7,
151.1, 146.4, 138.5, 123.7, 107.4, 104.8, 102.0, 72.1, 70.1, 69.1,
55.6, 34.7, 28.8 ppm; HRMS-EI calcd for C14H16NO6 (Mþ þ 1)
294.0978, found 294.1011.
Acknowledgment. The authors are grateful to the follow-
ing agencies for financial support of this work: Natural
J. Org. Chem. Vol. 75, No. 9, 2010 3083

Collins et al.
JOCArticle
Sciences and Engineering Research Council of Canada
(NSERC) (Idea to Innovation and Discovery Grants);
Canada Research Chair Program, Canada Foundation for
Innovation (CFI), Research Corporation, TDC Research,
Inc.; Brock University; and the Ontario Partnership for
Innovation and Commercialization (OPIC) and Lotte and
John Hecht Memorial Foundation grant to S.P. A.E.R. and
A.K. thank the National Institutes of Health (P20 RR016480)
for financial support and Professor Snezna Rogelj for her
kind assistance with the cell culture.
Supporting Information Available: Copies of 1H NMR and
13C NMR spectra for all new compounds. This material is
available free of charge via the Internet at http://pubs.acs.org.
3084 J. Org. Chem. Vol. 75, No. 9, 2010