Attempted oxidative deamination of N-deacetylcolchicinoids with 3,5- di(tert-butyl)-1,2-benzoquinone: Synthesis of 2h-1,4-benzoxazine-type adducts

Article abstract of DOI:10.1002/(SICI)1522-2675(19990908)82:9<1502::AID-HLCA1502>3.0.CO;2-J

In an attempt to use 3,5-di(tert-butyl)-1,2-benzoquinone for the oxidative deamination of N-deacetylcolchicine (4) and N- deacetylthiocolchicine (= N-deacetyl-10-demethoxy-10-(metbylthio)colchicine; 5) to give the corresponding ketones 2 and 3, the 2H-1,4-benzoxazine-type adducts 8/9 and 11/12, respectively, were formed instead, showing a new and unexpected behavior of Corey's reagent. The adducts were separated and spectroscopically characterized, and a plausible scheme of formation is reported.

Full text of DOI:10.1002/(SICI)1522-2675(19990908)82:9<1502::AID-HLCA1502>3.0.CO;2-J

1502
Helvetica Chimica Acta ± Vol. 82 (1999)
Attempted Oxidative Deamination of N-Deacetylcolchicinoids
with 3,5-Di(tert-butyl)-1,2-benzoquinone: Synthesis of
2H-1,4-Benzoxazine-Type Adducts
1
by Bruno Danieli )*, Giordano Lesma, Daniele Passarella, Davide Prosperi, and Alessandra Silvani
Dipartimento di Chimica Organica e Industriale, Universit aÁ degli Studi di Milano, via Venezian 21, I-20133
Milano
and Ezio Bombardelli
Indena S.p.A., Via Ortles 12, I-20143 Milano
In an attempt to use 3,5-di(tert-butyl)-1,2-benzoquinone for the oxidative deamination of N-deacetylcol-
chicine (4) and N-deacetylthiocolchicine (ˆ N-deacetyl-10-demethoxy-10-(methylthio)colchicine; 5) to give the
corresponding ketones 2 and 3, the 2H-1,4-benzoxazine-type adducts 8/9 and 11/12, respectively, were formed
instead, showing a new and unexpected behavior of Coreyꢀs reagent. The adducts were separated and
spectroscopically characterized, and a plausible scheme of formation is reported.
Introduction. ± Colchicine (ˆ(S)-N-(5,6,7,9-tetrahydro-1,2,3,10-tetramethoxy-9-
oxobenzo[a]heptalen-7-yl)acetamide; 1), one of the most important non-indole
alkaloids, possesses a notable antimitotic activity mainly applied for the treatment of
acute gout, amyloidosis of familial Mediterranean fever, and liver cirrhosis [1].
Moreover, colchicine shows a potent antileukemic activity in vitro, but its extreme
toxicity is a major obstacle in the effective clinical use for the treatment of neoplastic
diseases [2]. Therefore, the modification of the molecular structure of colchicine is an
active area of research, spurred by the possibility to improve the pharmaceutical profile
of the natural product by synthesizing less toxic and therapeutically more favorable
analogues and to unravel the complex structure-activity relationships.
1)
Tel: 02.2367606; fax: 02.2364369; e-mail: Danieli@icil64.cilea.it.

Helvetica Chimica Acta ± Vol. 82 (1999)
1503
In the frame of a systematic study on the pharmacological properties of new and
known colchicinoids, we intended to investigate extensively the biological properties of
the non-N-containing compounds 7-deacetamido-7-oxocolchicine (2), a metabolite of
colchicine [3], and 7-deacetamido-7-oxothiocolchicine (3), the so-called colchicone
and thiocolchicone, respectively (thiocolchicine ˆ 10-demethoxy-10-(methylthio)col-
chicine). Both compounds are readily prepared in excellent yield by oxidative
deamination of N-deacetylcolchicine (4) [4] and N-deacetylthiocolchicine (5) [5],
respectively, with the Rapoport reagent (4-formyl-1-methylpyridinium benzenesulfo-
nate) [6], following the protocol developed by Banwell et al. [4]. During our study, a
literature search revealed a limited number of synthetic reagents for the conversion of
primary amines to carbonyl compounds (for a leading reference, see [7]). Among
these, the readily available 3,5-di(tert-butyl)-1,2-benzoquinone (DTBQ; 6) developed
by Corey and Achiva [8] seemed to be very promising: it is reported to be an extremely
efficient reagent for the conversion of cyclohexylamine to cyclohexanone under mild
conditions.
In an attempt to use this reagent for the synthesis of 2 and 3 from 4 and 5,
respectively, we observed a different reaction outcome: unexpectedly the adducts 8/9
and 11/12, respectively, containing a 2H-1,4-benzoxazine moiety were formed. The
structure determination of 8, 9, 11, and 12 and a plausible mechanism of formation are
the object of the present report.
Results and Discussion. ± N-Deacetylcolchicine (4), obtained in 80% overall yield
from N-deacetyl-N-formylcolchicine (7) [9] by the methodology reported by Grieco
2
and co-workers for the hydrolysis of amides [10] ), was reacted with 1 equiv. of DTBQ
(6) in MeOH for 24 h. After hydrolysis with oxalic acid, the product mixture was
separated by chromatography, affording the expected colchicone (2) in only 6%
isolated yield. In addition two novel optically inactive compounds, 8 and 9, were
isolated in 22 and 6% yield, respectively, together with 50% of unreacted 4. The 2H-1,4-
benzoxazine-like structures of 8 and 9, derived by condensation of 4 with 6 followed by
functionalization at C(6), were established by spectroscopic means.
The MS of 8 exhibits a molecular ion at m/z 557, revealing immediately that a molecule of DTBQ is
1
incorporated into the colchicine moiety. In fact, the H-NMR spectrum shows the presence of 2 s (each 9 H) at d
1
.28 and 1.47 for two t-Bu groups, and of two aromatic protons (meta-oriented to each other) at d 7.19 and 7.25
J ˆ 3 Hz), in addition to the signals of the colchicine moiety (see Exper. Part). These NMR data, compared to
that of 1, suggest that a profound modification has occurred in the ring-B region of 8: the characteristic splitting
pattern of the ABCDX system due to CH (5), CH
(6), and H� C(7) of colchicinoids is missing and replaced by
(
2
2
an ABX system with signals at d 3.06, 3.29, and 4.88 (JAB ˆ 14 Hz, JAX ˆ JBX ˆ 3 Hz, apparent values). In the
1
3
C-NMR spectrum of 8, the presence of a benzylic methylene C-atom (t at d 36.0), an oxymethine C-atom (d at
2
d 75.8), and a non-protonated sp C-atom directly linked to a heteroatom (s at d 164.4) is suggested.
‡
.
The second reaction product 9 is simply the 10a-hydroxy derivative of 8 (M at m/z 573, 16 amu higher
1
13
than that of 8), as confirmed by the H- and C-NMR spectra, which show an AB system at d(H) 3.22 and 3.46
(
1
J ˆ 13.5 Hz) and a t at d(C) 35.0 for C(10), a s at d(C) 95.6 for an oxygenated C-atom (C(10a)), and a s at d(C)
2
64.6 for the substituted sp -C-atom (C(16a)).
2)
This methodology has been applied by Lebeau and co-workers to the deacetylation of cholchicine (1) [11].
However, in our hands, conversion of 1 to N-[(tert-butoxy)carbonyl]colchicine proceeded with
unsatisfactory yield (15 ± 20%), in spite of repeated experimentation.

1504
Helvetica Chimica Acta ± Vol. 82 (1999)
The N-deacetylthiocolchicine (5), easily available from thiocolchicine (10) [12],
behaved in a very similar way. On reaction with 1.1 equiv. of DTBQ (6), almost 48% of
unaffected starting material 10 was recovered, thiocolchicone (3) was formed in 5%
isolated yield, and 11 and 12, the thio analogoues of 8 and 9, were obtained in 24 and
5
% yield, respectively.
Scheme
The formation of the new 2H-1,4-benzoxazine derivatives may be explained in
terms of the pathway depicted in the Scheme. The condensation of 4 or 5 with DTBQ
6) proceeds uneventfully by initial condensation to the less hindered carbonyl group of
to form an intermediate o-quinone monoimine (A) [13]. This quinone monoimine
(
6
undergoes a rapid spontaneous [1,5]-prototropic shift to give a N-substituted
o-aminophenol represented as a mixture of the imine structure B and the enamine
structure B' the rearrangement being thermodynamically favored by the aromatization
of the o-quinone-monoimine system [13]. In the presence of the high potential of
3
DTBQ (6) ), the intermediate N-substituted o-aminophenol B/B' is oxidized to
another quinonoid state, generating the transient enamine-derived o-quinonemono-
3)
For leading references concerning the use of high-potential quinones in the oxidation and dehydrogena-
tion of N-compounds, see [14].

Helvetica Chimica Acta ± Vol. 82 (1999)
1505
4
imine C which, by electrocyclization, leads to the 1,4-benzoxazines 8 or 11 ). The
hydroxylated products 9 and 12 are formed by further oxidation of 8 and 11,
respectively, with DTBQ, presumably via an 1,4-benzoxazinium cation that is isolated
in the hydrated form.
The reaction outcome is likely to result from a slow step of the initial condensation,
compared with a fast step of dehydrogenation of the imine/enamine intermediates B/B'
to form the enamine-derived o-quinone monoimine C. In fact, using 1.1 equiv. of
DTBQ (6), the first formed aminophenol is readily further oxidized to the 1,4-
benzoxazines, thus leaving most of the starting material unaffected. Acid hydrolysis of
this reaction mixture allows only a small amount of the 7-ketones 2 and 3 to be isolated.
With 2.1 equiv. of 6, the ketones and starting amines were still obtained, although in
small quantity, together with a substantial amount of the 2H-1,4-benzoxazine and 2H-2-
hydroxy-1,4-benzoxazine derivatives. These benzoxazine derivatives are the only
products isolated when 3.1 equiv. of 6 are used.
The behavior of 4 and 5 is different from that of cyclohexylamine and related
amines, where an almost quantitative yield of the corresponding ketones is obtained
after hydrolysis [9][13]. In an attempt to explain this difference, the tetrahydronaph-
thalin-2-amine 13 [16] was subjected to excess (3 equiv.) DTBQ (6) giving rise to a
complex reaction mixture from which the only isolated product was the adduct 14,
albeit obtained in only 25% yield. No 3,4-dihydronaphthalin-2(1H)-one or other
reaction products could be detected. The above results suggest that the formation of the
benzoxazine products from 4, 5, and 13 is probably dependent on conjugation with the
neighboring aromatic systems and the probable presence of the intermediate N-
substituted o-aminophenol in solution in the enamine form B', which is readily oxidized
by DTBQ (6) to the enamine-derived o-quinone monoimine C [14]. At variance, in the
case of cyclohexylamine, it has been shown [13] that the N-substituted o-aminophenol
exists as the aromatic Schiff base B.
In conclusion, the oxidative deamination of N-deacetylcolchicine (4) and
N-deacetylthiocolchicine (5) with 3,5-di(tert-butyl)-1,2-benzoquinone (DTBQ; 6)
failed to give the corresponding ketones. Instead, the new adducts 8, 9, 11, and 12
were obtained by the electrocyclic reaction of an intermediate enamine-derived o-
quinone monoimine species, thus featuring an unprecedented reactivity of DTBQ. By
4)
The formation of a 1,4-benzoxazine has never been observed in the oxidative deamination of amines by
DTBQ (6). The formation of a 2H-1,4-benzoxazine has been reported during the reaction of 2,4-di(tert-
butyl)-6-(methoxyimino)cyclohexa-2,4-dien-1-one with trans-stilbene [15].

1506
Helvetica Chimica Acta ± Vol. 82 (1999)
this reaction, derivatives of the colchicine nucleus functionalized at position 6 have
been obtained for the first time.
Evaluation of 8, 9, 11, and 12 as inhibitors of tubulin polymerization indicated that
the compounds are devoid of any activity.
Experimental Part
General. The 3,5-di(tert-butyl)-1,2-benzoquinone was purchased from Aldrich. Colchicine (1), N-deacetyl-
N-formyl colchicine (7), and thiocolchicine (10) were a gift of Indena, S.p.A., Milano. All solvents were distilled
and properly dried prior to use. During usual workup, all org. extracts were dried (Na
evaporated. Thin layer chromatography (TLC) for reaction monitoring: Merck silica gel 60 F254 plates;
detection under UV light or spraying with Pancaldi reagent ((NH MoO , Ce(SO , H SO , H O) or alkaline
KMnO soln. Flash column chromatography (FC): Merck silica gel 60 (230 ± 400 mesh). M.p.: Kofler hot-bench
apparatus. H- and C-NMR Spectra: Bruker AC300 (300 and 75.2 MHz, resp.); in CDCl
ppm relative to SiMe
(ˆ 0 ppm) as an internal standard, coupling constants J in Hz (apparent values). MS: VG-
070EQ-HF instrument (EI, 70 eV); m/z (rel. intensity in %).
N-Deacetylcolchicine (ˆ(S)-7-Amino-6,7-dihydro-1,2,3,10-tetramethoxybenzo[a]heptalen-9(5H)-one; 4).
To a soln. of N-deacetyl-N-formylcolchicine (7; 3 g, 7.8 mmol) [8] and 4-(dimethylamino)pyridine (DMAP; 1 g,
.2 mmol) in CH Cl (30 ml), di(tert-butyl) pyrocarbonate (9.85 g, 45 mmol) was added at r.t. Stirring was
continued for 24 h, then the temp. was increased to 408, and di(tert-butyl) pyrocarbonate (9.85 g, 45 mmol) and
DMAP (1 g, 8.2 mmol) in CH Cl (20 ml) were added. After washing with H O and workup, the residue was
purified by FC (AcOEt) to yield N-[(tert-butoxy)carbonyl]-N-deacetyl-N-formylcolchicine (3.21 g, 85%).
2 4 2 4
SO or Mg SO ) and
4
)
6
4
4
)
2
2
4
2
4
1
13
3
; chemical shifts d in
4
7
8
2
2
2
2
2
Yellow solid. M.p. 95 ± 998. TLC (AcOEt/acetone 8 : 2): R
f
0.42. 1H-NMR: 9.21 (s, 1 H); 7.20 (s, 1 H); 7.15
(
(
d, J ˆ 10.3, 1 H); 6.74 (d, J ˆ 10.3, 1 H); 6.52 (s, 1 H); 5.00 ± 5.15 (m, 1 H); 3.96 (s, 3 H); 3.93 (s, 3 H); 3.89
‡
s, 3 H); 3.63 (s, 3 H); 2.45 ± 2.65 (m, 3 H); 1.9 ± 2.0 (m, 1 H); 1.55 (s, 9 H). HR-MS: 485.2078 (C26
H
31NO ; calc.
8
4
85.2050).
N-[(tert-Butoxy)carbonyl]-N-deacetyl-N-formylcolchicine (3.21 g, 6.62 mmol) in MeOH (20 ml) was
added portionwise to a soln. of MeONa in MeOH (0.57 g of Na (24.78 mmol) in 60 ml of MeOH) at 08.
After 1 h, the soln. was neutralized by adding solid NH Cl. Evaporation and extraction with CH Cl afforded
4
2
2
pure N-[(tert-Butoxy)carbonyl]-N-deacetylcolchicine (2.06 g, 98%). Pale yellow solid. M.p. 80 ± 848. TLC
1
(
(
(
AcOEt/hexane 9 :1): R
f
0.12. H-NMR: 7.58 (s, 1 H); 7.27 (d, J ˆ 10.3, 1 H); 6.83 (d, J ˆ 10.3, 1 H); 6.53
s, 1 H); 4.98 (d, J ˆ 7.5, NH); 4.41 (m, 1 H); 4.01 (s, 3 H); 3.93 (s, 3 H); 3.90 (s, 3 H); 3.68 (s, 3 H); 2.2 ± 2.6
‡
m, 4 H); 1.40 (s, 9 H). HR-MS: 429.2167 (C24
H
31NO ; calc. 429.2151).
6
A soln. of N-[(tert-butoxy)carbonyl]-N-deacetylcolchicine (1.36 g, 2.98 mmol) in CH
2 2
Cl (30 ml) and
CF
3
COOH (3.3 ml) was stirred at r.t. under N for 5 h. Evaporation, addition to toluene (50 ml), and evaporation
2
gave a residue which was extracted wtih CH
MeOH 19 :1) gave 4 (1.04 g, 98%). M.p. 141 ± 1468. TLC (CH
2
Cl
2
in the presence of aq. ammonia. FC purification (CH
2
Cl
2
/
1
2
Cl
2
/MeOH 9 :1): R
f
0.36. H-NMR: 7.87 (s, 1 H);
7
.46 (d, J ˆ 10.3, 1 H); 7.00 (d, J ˆ 10.3, 1 H); 6.61 (s, 1 H); 4.20 (m, 1 H); 3.94 (s, 3 H); 3.93 (s, 3 H); 3.92
‡
(
s, 3 H); 2.6 ± 2.8 (m, 1 H); 2.3 ± 2.5 (m, 1 H). HR-MS: 357.1587 (C20
H
23NO ; calc. 357.1576).
5
General Procedure for the Reaction of N-Deacetylcolchicine (4), N-Deacetylthiocolchicine (5), and 1,2,3,4-
Tetrahydronaphthalen-2-amine (13) with 3,5-Di(tert-butyl)-1,2-benzoquinone (6). To a soln. of 4, 5, or 13 [13]
0.14 mmol) in MeOH (1 ml), 3,5-di(tert-butyl)-1,2-benzoquinone (6; 34 mg, 0.15 mmol) was added under N
Stirring was continued for 24 h, then THF (1 ml) and a soln. of oxalic acid (25 mg, 0.20 mmol) in H O (0.5 ml)
was added. After 24 h, the hydrolysis was complete, the solvents were evaporated, and the residue taken up in
O and extracted with CH Cl . The residue of the reaction of 4 was chromatographed (CH Cl /MeOH 19 :1)
to give 2 (6%), 8 (22%), 9 (6%), and unreacted 4 (50%). The residue of the reaction of 5 was chromatographed
hexane/AcOEt 7:3) to give 3 (5%), 11 (24%), 12 (5%), and unreacted 5 (48%). The residue of the reaction of
3 was chromatographed (CHCl ) to give 14 (30%).
With 2.1 equiv. of 6, isolated yields were from 4: 2 (4%), 8 (48%), 9 (15%), and recovered 4 (6%); from 5: 3
5%), 11 (51%), 12 (14%), and recovered 5 (5%). With 3.1 equiv. of 6, isolated yields were from 4: 8 (58%) and
(14%); from 5: 11 (60%) and 12 (17%).
,6-Dihydro-1,2,3,10-tetramethoxybenzo[a]heptalene-7,9-dione (2): Yellowish solid. M.p. 2318. TLC
(
2
.
2
H
2
2
2
2
2
(
1
3
(
9
5
1
13
(
(
CH
2
Cl
2
/MeOH 9 :1): R
f
0.62. H- and C-NMR: identical to those reported in [3][4]. HR-MS: 356.1283
‡
C
20
H
20O ; calc. 356.1260).
6

Helvetica Chimica Acta ± Vol. 82 (1999)
1507
1
2,14-Di(tert-butyl)-10,10a-dihydro-3,6,7,8-tetramethoxy-2H-benzo[4,5]heptaleno[2,1-b][1,4]benzoxazin-
1
2
-one (8): Pale-yellow solid. M.p. 148 ± 1498. TLC (CH
2
Cl
2
/MeOH 11:1): R
f
0.48. H-NMR: 7.54 (s, 1 H); 7.31
(
4
d, J ˆ 11, 1 H); 7.25 (d, J ˆ 3, 1 H); 7.19 (d, J ˆ 3, 1 H); 6.85 (d, J ˆ 11, 1 H); 6.65 (s, 1 H); 4.88 (t, J ˆ 3, 1 H);
.01 (s, 3 H); 3.87 (s, 3 H); 3.82 (s, 3 H); 3.52 (s, 3 H); 3.29 (dd, J ˆ 14, 3, 1 H); 3.06 (dd, J ˆ 14, 3, 1 H); 1.40
13
(
s, 9 H); 1.28 (s, 9 H). C-NMR: 178.8 (CO); 164.4 (C(16a)); 164.2 (C(3)); 153.0, 151.5 (C(6), C(8)); 147.0
(C(11a)); 144.4 (C(7)); 142.6 (C(15a)); 141.7 (C(5a)); 137.6 (C(1)); 136.4 (C(9a)); 136.1 (C(5)); 133.1 (C(12));
133.0 (C(16b)); 131.6 (C(14)); 125.1 (C(5b)); 124.0, 123.0 (C(13), C(15)); 112.1 (C(4)); 109.1 (C(9)); 75.8
(
(
C(10a)); 61.2, 61.1 (MeO� C(6), MeO� C(7)); 56.1, 55.8 (MeO� C(3), MeO� C(8)); 36.0 (C(10)); 34.7, 34.4
‡
Me
3
C� C(12), Me
3
C� C(14)); 31.4, 29.7 (2 Me
3
C). HR-MS: 557.2789 (C34
H
39NO ; calc. 557.2777).
6
1
2,14-Di(tert-butyl)-10,10a-dihydro-10a-hydroxy-3,6,7,8-tetramethoxy-2H-benzo[4,5]heptaleno[2,1-b][1,4]-
1
benzoxazin-2-one (9): Pale-yellow solid. M.p. 1788. TLC (CH
2 2 f
Cl /MeOH 11:1): R 0.28. H-NMR: 7.69 (s, 1 H);
7
.60 (d, J ˆ 1.4, 1 H); 7.40 (d, J ˆ 1.4, 1 H); 7.31 (d, J ˆ 11, 1 H); 6.86 (d, J ˆ 11, 1 H); 6.65 (s, 1 H); 4.00 (s, 3 H);
3.86 (s, 3 H); 3.81 (s, 3 H); 3.50 (s, 3 H); 3.46 (d, J ˆ 13.5, 1 H); 3.22 (d, J ˆ 13.5, 1 H); 1.47 (s, 9 H); 1.28
13
(
s, 9 H). C-NMR: 178.8 (CO); 164.6 (C(16a)); 162.6 (C(3)); 153.4, 151.4 (C(6), C(8)); 146.4 (C(11a)); 144.6
(C(7)); 141.9 (C(15a)); 140.2 (C(5a)); 138.5 (C(1)); 137.4 (C(9a)); 136.0 (C(5)); 133.4 (C(12)); 131.2 (C(16b));
1
(
Me
30.1 (C(14)); 125.6 (C(5b)); 124.4, 123.3 (C(13), C(15)); 114.5 (C(4)); 109.0 (C(9)); 95.7 (C(10a)); 61.1, 60.6
MeO� C(6), MeO� C(7)); 56.4, 55.8 (MeO� C(3), MeO� C(8)); 35.0 (C(10)); 34.5, 34.2 (Me
3
C� C(12),
‡
3
C� C(14)); 31.4, 29.9 (2 Me
3
C). HR-MS: 573.2726 (C34
H
39NO ; calc. 573.2735).
7
5
,6-Dihydro-1,2,3-trimethoxy-10-(methylthio)benzo[a]heptalene-7,9-dione (3): Yellow solid. M.p. 231 ±
1
13
2
358. TLC (AcOEt/hexane 4 :1): R
f
0.54. TLC (CH
2
Cl
2
/MeOH 9 :1): R
‡
20 5
H O S ; calc. 388.0980).
f
0.61. H- and C-NMR: identical to
those reported in [5]. HR-MS: 388.0987 (C20
1
2,14-Di(tert-butyl)-10,10a-dihydro-6,7,8-trimethoxy-3-(methylthio)-2H-benzo[4,5]heptaleno[2,1-b][1,3]-
1
benzoxazin-2-one (11): Yellow solid. M.p. 106 ± 1088. TLC (hexane/AcOEt 1:1): R
f
0.47. H-NMR: 7.35 (s, 1 H);
7
1
.30 (d, J ˆ 11, 1 H); 7.27 (d, J ˆ 3, 1 H); 7.20 (d, J ˆ 3, 1 H); 7.09 (d, J ˆ 11, 1 H); 6.64 (s, 1 H); 4.87 (t, J ˆ 4,
H); 3.87 (s, 3 H); 3.83 (s, 3 H); 3.53 (s, 3 H); 3.30 (dd, J ˆ 14, 4, 1 H); 3.06 (dd, J ˆ 14, 4, 1 H); 2.45 (s, 3 H);
1
3
1
1
(
.41 (s, 9 H); 1.28 (s, 9 H). C-NMR: 182.3 (CO); 164.7 (C(16a)); 159.8 (C(3)); 153.8 (C(8)); 152.1 (C(6));
47.2 (C(16b)); 144.9 (C(11a)); 143.2 (C(15a)); 142.3 (C(7)); 137.0 (C(5a)); 136.1 (C(5)); 135.5 (C(9a)); 135.1
C(1)); 133.6 (C(12)); 132.3 (C(14)); 126.8 (C(4)); 125.8 (C(5b)); 124.6, 123.6 (C(13), C(15)); 109.8 (C(9));
7
(
5
6.5 (C(10a)); 61.8, 61.6 (MeO� C(6), MeO� C(7)); 56.4 (MeO� C(8)); 36.6 (C(10)); 35.2, 35.0
‡
Me
73.2549).
2,14-Di(tert-butyl)-10,10a-dihydro-10a-hydroxy-6,7,8-trimethoxy-3-(methylthio)-2H-benzo[4,5]heptale-
no[2,1-b][1,4]benzoxazin-2-one (12): Yellow solid. M.p. 2288. TLC (hexane/AcOEt 7:3): R
0.40. 1H-NMR:
.47 (s, 1 H); 7.38 (d, J ˆ 2.5, 1 H); 7.30 (d, J ˆ 2.5, 1 H); 7.26 (d, J ˆ 10, 1 H); 7.07 (d, J ˆ 10); 6.66 (s, 1 H); 3.85
3
C� C(12), Me
3
C� C(14)); 31.9, 30.3 (2 Me
3
C); 15.7 (MeS). HR-MS: 573.2568 (C34
H
39NO
5
S ; calc.
1
f
7
(
(
(
s, 3 H); 3.82 (s, 3 H); 3.50 (s, 3 H); 3.38 (d, J ˆ 13, 1 H); 3.24 (d, J ˆ 13, 1 H); 2.46 (s, 3 H); 1.48 (s, 9 H); 1.26
13
s, 9 H). C-NMR: 182.0 (CO); 163.4 (C(16a)); 160.1 (C(5)); 154.1 (C(8)); 152.0 (C(6)); 147.3 (C(16a)); 144.9
C(15a)); 142.5 (C(7)); 141.1 (C(9a)); 137.9 (C(5a)); 136.3 (C(5)); 136.3 (C(1)); 131.9 (C(12)); 131.2 (C(14));
1
27.2 (C(4)); 126.3 (C(5b)); 124.9, 124.0 (C(13), C(15)); 109.8 (C(9)); 96.3 (C(10a)); 61.9, 61.7 (MeO� C(6),
MeO� C(7)); 56.5 (MeO� C(8)); 43.7 (C(10)); 35.7, 35.1 (Me
3
C� C(12), Me
3
C� C(14)); 31.4, 30.6 (2 Me
3
C);
‡
1
5.8 (MeS). HR-MS: 589.2506 (C34
H
39NO
6
S ; calc. 589.2498).
9
,11-Di(tert-butyl)-5,10-dihydro-6H-benzo[c]phenoxazine (14): Amorphous solid. TLC (CHCl
3
): R 0.55.
f
1
H-NMR: 7.81 (dd, J ˆ 2.5, 1, 1 H); 7.52 (d, J ˆ 2, 1 H); 7.3 ± 7.5 (m, 3 H); 7.23 (d, J ˆ 2, 1 H); 3.53 (t, J ˆ 7.5,
‡
2
H); 3.27 (t, J ˆ 7.5, 2 H); 1.44 (s, 9 H); 1.37 (s, 9 H). HR-MS: 347.2271 (C24
H
29NO ; calc. 347.2249).
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Received May 20, 1999