Phototransformations of some 3-cyclohexenyloxychromenones: Synthesis of Spirocyclic compounds

Article abstract of DOI:10.1002/jccs.201800329

The phototransformation of the 3-cyclohexenyloxychromenones by irradiation with a pyrex-filtered light from a 125 W Hg vapor lamp under an inert atmosphere into the spirocyclic fused xanthenones was described. The efficacy of the protocol depended upon th

Full text of DOI:10.1002/jccs.201800329

Received: 10 September 2018
DOI: 10.1002/jccs.201800329
Revised and accepted: 30 November 2018
A R T I C L E
Phototransformations of some 3-cyclohexenyloxychromenones:
Synthesis of Spirocyclic compounds
Radhika Khanna1 | Aarti Dalal2 | Urmila Berar3 | Sandeep Singh2 | Ramesh C. Kamboj2
1Department of Chemistry, MMEC, Maharishi
The phototransformation of the 3-cyclohexenyloxychromenones by irradiation with
Markandeshwar (Deemed to be university),
Mullana, Ambala, Haryana, India
a pyrex-filtered light from a 125 W Hg vapor lamp under an inert atmosphere into
the spirocyclic fused xanthenones was described. The efficacy of the protocol
depended upon the position (o-, m-, or p-) of the cyclohexenyloxy group appended
to the 2-aryl moiety on the chromenone nucleus, which was further invoked by
steric, electronic, and proximity considerations. The structure(s) of the substrates
and photoproducts were established using the spectroscopic (IR and NMR) data.
2Department of Chemistry, Kurukshetra
University, Kurukshetra, Haryana, India
3Department of Chemistry, UIET, Kurukshetra
University, Kurukshetra, Haryana, India
Correspondence
Ramesh C. Kamboj, Department of Chemistry,
Kurukshetra University, Kurukshetra, Haryana
136119, India.
KEYWORDS
Email: rckamboj@hotmail.com
1,4-biradical, cyclohexenyloxychromenones, irradiation, spirocyclics
Funding information
University Grants Commission (UGC), New Delhi;
Maharishi Markandeshwar (Deemed to be
university); Biotechnology Industry Research
Assistance Council (BIRAC), New Delhi
synthesized.[10,11,22,23] In corollary, following the previous
1
| INTRODUCTION
work achievement, in the present work we have designed
variously substituted cycloalkenyloxychromones (1, 2) by
their conversion into spirocyclics for generalizing their syn-
thesis by the photochemical route.
The utility of H-abstractions in organic synthesis has found
applications in the synthesis of many interesting compounds
including vinyl ethers,[1] spiropyrans,[2,3] and polycyclic
compounds;[4–8]. Among these, the most important applica-
tion is the one-step synthesis of spiropyrans (a class of spiro-
cyclic compounds).[2,9–11] Spirocompounds are of great
interest as they have interesting conformational features and
biological activities[12–15] that were endowed to the asym-
metric characteristics due to chiral spirocarbon of these mol-
ecules. Spirocyclic compounds encompass a wide range of
natural entities isolated from various sources[16–20] including
the phytochemicals (alkaloids, lactones, terpenoids etc.).
The spirocompounds had applications in the field of liq-
uid crystals due to the photochromism.[21] Being of perva-
sive significance, their synthesis using conventional thermal
methods has been the subject of many studies but these
methods lack generality due to multistep reactions and nona-
vailability of their starting materials. In this context, our lab-
oratory has utilized the Norrish Type-II process for the
synthesis of spirocyclics, which proved to be a simple, effi-
cient, and economical method and various furyl-substituted
O
O
R
O
O
a, p- or 4'-cyclohexenyloxy;
b, m- or 3'-cyclohexenyloxy;
c, o- or 2'-cyclohexenyloxy;
1, R = H
2, R = Cl
2
|
RESULTS AND DISCUSSION
and were synthesized from the
The targets
1
2
3-hydroxychromenones (Scheme 1) by alkylation with
3-bromocyclohexene in the presence of anhyd. K2CO3, dry
acetone, and tetra-n-butylammonium iodide as phase transfer
and
phenyl-substituted
spirocyclics
have
been
© 2019 The Chemical Society Located in Taipei & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
J Chin Chem Soc. 2019;1–6.
http://www.jccs.wiley-vch.de
1

2
KHANNA ET AL.
OH
(ii)
TABLE 1 Yield (%) of photoproducts 3a, 3b, 5a, and 5b
OH
CHO
OH
O
OH
O
O
O
+
(i)
Photoproducts
Yield (%)
R
R
R
R
OH
OH
3a
3b
5a
5b
17
17
25
22
(iii)
O
i) EtOH / base[KOH or Ba(OH)2] ;
ii) KOH / H2O2 (30%);
O
O
iii) anhyd. K2CO3 / Dry Acetone / Bu4N+I-
/
Br
O
J7,6 = J7,8 = 9.0 Hz, H-7). The four protons of the phenyl
ring at C2 gave signals as two doublets at δ 7.89
1, R =
H
2, R = Cl
a, p- or 4'-cyclohexenyloxy;
b, m- or 3'-cyclohexenyloxy;
c, o- or 2'-cyclohexenyloxy;
(d, J2 ,3 = J6 ,5 = 8.5 Hz, H-20
&
H-60) and 6.89
0
0
0
0
(d, J3 ,2 = J5 ,6 = 8.5 Hz, H-30 & H-50). The cyclohexene
0
0
0
0
SCHEME 1 Synthesis of chromenones 1 and 2
protons H-300, H-200, and H-100 appeared at δ 5.95 (dt,
J3 ,2 = 9.5 Hz, J3 ,4 = 3.5 Hz, H-300), 5.80 (1H, dd,
00 00
00 00
catalysts (PTCs). Structures of these 3-cyclohexenyloxy
chromones were established using their spectroscopic data
(vide experimental).
Irradiation of the 3-cyclohexenyloxy chromones (1, 2)
with pyrex-filtered light from a 125 W medium pressure Hg
lamp in dry benzene (Scheme 2) furnished photoproducts 3
(a, b), 4(a, b), 5(a, b), and 6(a, b). No photoproducts corre-
sponding to 3, 4, 5, and 6 were obtained from the irradiation
of 1c and 2c.
The formation of photoproducts 3, 4, 5, and 6 was ascer-
tained using their IR and NMR data. The compound 3a
showed a strong absorption peak at 1,620 cm−1 in the IR
spectrum confirming the presence of a carbonyl group. In
J2 ,3 = 9.5 Hz, Jvic = 5.5 Hz, H-200), and 4.80 (1H, m, H-
00 00
100), respectively. The remaining six protons H-400, H-500, and
H-600 of cyclohexene were revealed at δ 2.10–1.60. The
structures of other photoproducts were ascertained likewise
using the spectroscopic data (vide experimental).
2'
2'
O
O
1
8
5
O
O
O
O
4'
10
4
4"
2"
6'
H
OH
H
O
8
6
4"
2"
4a
3a
1
the H NMR spectrum of 3a, the protons H-8, H-9, H-11,
and H-10 were found to be placed at δ 8.28 (d,
The yields (%) of the photoproducts 3a and 5a were
found to be higher than those of 3b and 5b (Table 1) in these
photoconversions. This may be due to the statistical factor,
as in the 3-cyclohexenyloxy chromones 1a and 2a, two sites
(20- and 60-positions) are available for coupling of 3-alkoxy
carbon atoms in comparison to 1b and 2b, which have the
propensity of cyclization preferentially at the 60-position of
the 2-aryl moiety (Figure 1), the position 20 being sterically
more crowded due to the tethering of the 30-cyclohexenyloxy
group. The perusal of the structures of the spirocyclics 3b
and 5b obtained here showed that these have been produced
through the regioselective cyclization at the 60-position of
the aryl moiety simulating the regioselective behaviur of
photocyclization in 3-alkoxychromenones as observed
J8,9 = 7.8 Hz), 7.66 (dt, J9,11 = 1.5 Hz, J9,8 = J9,10
=
8.7 Hz), 7.54 (dd, J11,9 = 1.5 Hz, J11,10 = 8.4 Hz), and 7.40
(dt, J10,8 = 1.5 Hz, J10,9 = J10,11 = 8.7 Hz), respectively.
The protons of ring D were found at δ 8.01 (d,
J1,2 = 8.4 Hz, H-1), 7.00 (dd, J2,1 = 8.4 Hz, J2,4 = 2.6 Hz,
H-2), and 6.80 (d, J4,2 = 2.6 Hz, H-4). The protons H-200, H-
20, H-30, and H-100 were showed as multiplets at δ 6.35 and
6.10–5.60, respectively. The remaining 12 protons were
found in the aliphatic region between δ 2.40–1.60 as a multi-
plet (12H, H-40, H-50, H-60, H-300, H-400, and H-500). The pho-
toproduct 4a was confirmed from its IR and 1H NMR
spectral data. A strong absorption peak at 1,600 and
3,270 cm−1 in the IR spectrum confirmed the presence of
1
carbonyl and hydroxyl groups, respectively. In the H NMR
spectrum, the benzenoid ring protons displaced resonances
at their usual place i.e. δ 8.10 (d, J5,6 = 9.0 Hz, H-5), 7.60
(dt, J6,8 = 1.5 Hz, J6,7 = J6,5 = 9.0 Hz, H-6), 7.50 (dd,
J8,6 = 1.5 Hz, J8,7 = 9.0 Hz, H-8), and 7.35 (dd,
O
O
2'
2'
O
O
6'
6'
R
O
R
O
2'
O
O
4
2'
1
O
O
2'
O
8
5
D
O
O
4'"
O
B
2'"
4'
10
8
5
O
6'
4"
2"
C
A
8
6'
R
O
R
O
6
R
OH
4"
2"
b, m- or 3'-cyclohexenyloxy
O
a, p- or 4'-cyclohexenyloxy
2"
O
4(a, b)
6(a, b)
3(a, b)
5(a, b)
4"
H
a, p- or 4'-cyclohexenyloxy;
b, m- or 3'-cyclohexenyloxy;
c, o- or 2'-cyclohexenyloxy
1, R =
1, R = H
2, R = Cl
2, R = Cl
SCHEME 2 Photolysis of chromenones 1 and 2
FIGURE 1 Probable sites for clipping

KHANNA ET AL.
3
FIGURE 2 MM2 energy-minimized structures of (a–c)
TABLE 2 Close contact values (Å) for the conformations derived from the
MM2 program
photoconversions of the 3-cyclohexenyloxychromones 1(a,
b) and 2(a, b) to spirocyclic photoproducts 3(a, b) and 5(a,
b) may be visualized to occur through the initial formation
of a 1,4-biradical via the γ-H abstraction mechanism[24–28]
Close contact
values (Å)
between
carbonyl
oxygen and
the γ-H
Close contact
values (Å)
between the
γ-C radical
and 60-C of
2-phenyl ring
Position of the
cyclohexenyloxy
group at 2-aryl
moiety
_
followed by ring closure through the coupling of –O–CH–
Chromones
R
radicals with the 60-position of the 2-aryl moiety with the
subsequent fast expulsion of two hydrogens from enol [25–29]
to furnish the final spirocyclic photoproducts. The dealkoxy-
lation observed in the formation of 4 and 6 from 1 and 2 has
been conceived to occur through the formation of oxetane
followed by its fragmentation (concerted or stepwise) as
observed earlier in photochemical cycloreversion of oxetane
dyads[30] and 3-alkoxychromenones.[28]
1a
1b
1c
2a
2b
2c
H
Para-
2.508
2.451
2.348
2.428
2.400
2.349
3.598
3.683
3.881
3.692
3.741
3.884
H
Meta-
Ortho-
Para-
H
Cl
Cl
Cl
Meta-
Ortho-
earlier.28 This photocyclization is also in accordance with a
directive influence observed in free radical aromatic substi-
tution (o-directing and p-directing). The regioselectivity for
ring formation has been directed exclusively at the 60-
position that is para to the cyclohexenyloxy group and ortho
to the chromenyl group. No photoproducts were realized
through the regioselective cyclization at the 20-position.
The chromones 1c and 2c having the cycloalkenyloxy
group at the ortho position in the phenyl moiety appended to
C-2 did not yield any such products whatsoever upon photo-
irradiation, this can due to the steric effects that may be
explained on the basis of calculations of close contacts
derived from the energy-minimized structures (Figure 2)
obtained from the MM2 program. These close contact values
are listed in Table 2. It is evident from the table that when
the C-2 phenyl group in the chromones has a cyclohexeny-
loxy group at the ortho position, steric repulsion is encoun-
tered and the distance of the cyclohexenyloxy carbon that is
going to clip with the phenyl group carbon (60-position) is
longer that is, 3.881 and 3.884 Å in structures 1c and 2c,
respectively. But in the case of other chromones, these clip-
ping atoms are in close proximity as the close contact values
are of smaller extent (in 1a = 3.598 Å, 1b = 3.683 Å,
2a = 3.692 Å, and 2b = 3.741 Å, Table 2).
O
O
2'
2'
8
5
8
5
O
O
O
4'"
4'"
2'"
2'"
6'
6'
R
O
R
O
OH
2"
2"
1,4-Biradical
O
2'
8
O
4'"
2'"
6'
R
O
5
OH
2"
2'
O
1
O
O
4'
10
H
R
O
8
6
4"
2"
H
2'
O
1
O
4'
10
4
The cyclohexenyloxy group present in this chromenones
did not show its own intermolecular and intramolecular pho-
R
O
8
6
4"
2"
O
tochemistry
through
[2 + 2]
cycloaddition.These

4
KHANNA ET AL.
0
0
0
0
0
3
|
CONCLUSIONS
(2H, m, H-7, H-5 ), 6.90 (1H, ddd, J4 ,6 = J4 ,2 = 2.4 Hz,
J4 ,5 = 8.4 Hz, H-40), 6.01 (2H, m, H-200, H-2000), 5.89 (2H,
m, H-300, H-3000), 4.09 (2H, m, H-100, H-1000), and 2.20–1.50
(12 protons of cyclohexene rings).
Compound 1c: Yield 0.23 g (56%), yellow semisolid;
vmax (cm−1) 1,620 (C=O); δH (CDCl3): 8.12 (1H, dd,
J5,7 = 1.5 Hz, J5,6 = 8.1 Hz, H-5), 7.71 (1H, d,
J6 ,5 = 7.5 Hz, H-60), 7.65 (1H, dt, J6,8 = 1.5 Hz,
J6,5 = J6,7 = 8.1 Hz, H-6), 7.45–7.36 (2H, m, H-7, H-40),
7.10 (1H, dd, J8,6 = 1.5 Hz, J8,7 = 8.1 Hz, H-8), 6.88 (2H,
m, H-30, H-50), 5.77 (4H, m, H-200, H-2000, H-300, H-3000), 4.78
(2H, m, H-100, H-1000), and 2.01–1.49 (12 protons of cyclo-
hexene rings).
0
0
The phototransformation of the 3-cyclohexenyloxychrome-
nones furnished the spirocyclics. The efficacy of the process
depended upon the position (o-, m-, or p-) of the cyclohexe-
nyloxy group appended to the 2-aryl moiety on the chrome-
none nucleus. These findings were supported by the steric,
electronic, and proximity considerations.
0
0
4
| EXPERIMENTAL
1
The nuclear magnetic resonance H NMR (300 MHz) and
proton-decoupled 13C NMR (75.4 MHz) spectra were
recorded on a Bruker spectrometer using TMS as the inter-
nal standard. The infrared (IR) spectra were scanned in
KBr pellets on a MB3000 FT-IR with HORIZON MB™
FTIR software from ABB Bomen. Melting points were
determined in open capillaries and are uncorrected. The
irradiation of the deaerated solution of substrates was car-
ried out using a pyrex-filtered light from a 125 W
(medium pressure) Hg-vapor lamp under a nitrogen atmo-
sphere. The columns for chromatographic separation were
packed in pet ether with silica gel and were eluted with pet
ether and ethyl acetate mixture (99:1). The yields reported
are based on the amount of isolated photoproducts and
have been calculated by excluding the recovered
substrates.
Compound 2a: Yield 1.7 g (37%), yellow semisolid; vmax
) 1,639.8 (C=O); δH (CDCl3) 8.13 (1H, d,
(cm−1
0
0
0
0
J5,7 = 2.7 Hz, H-5), 8.05 (2H, d, J2 ,3 = J6 ,5 = 9.0 Hz, H-
20, H-60), 7.53 (1H, dd, J7,8 = 9.0 Hz, J7,5 = 2.7 Hz, H-7),
7.40 (1H, d, J8,7 = 9.0 Hz, H-8), 6.95 (2H, d,
J3 ,2 = J5 ,6 = 9.0 Hz, H-30, H-50), 5.95 (2H, m, H-200, H-
2000), 5.80 (2H, m, H-300, H-3000), 4.85 (2H, m, H-100, H-1000),
and 2.10–1.41 (12Hs, m, cyclohexene ring protons).
0
0
0
0
Compound 2b: Yield 1.3 g (45%), yellow semisolid; vmax
) 1,641.8 (C=O); δH (CDCl3) 8.13 (1H, d,
(cm−1
0
0
0
0
J5,7 = 2.4 Hz, H-5), 7.64 (1H, t, J2 ,4 = J2 ,6 = 2.1 Hz, H-
20), 7.58 (1H, ddd, J6 ,5 = 8.1 Hz, J6 ,4 = J6 ,2 = 2.1 Hz,
0
0
0
0
0
0
H-60), 7.53 (1H, dd, J7,8 = 8.7 Hz, J7,5 = 2.4 Hz, H-7), 7.41
0
0
(1H, d, J8,7 = 8.7 Hz, H-8), 7.31(1H, t/dd, J5 ,4 = 8.1 Hz,
H-50), 6.98 (1H, ddd, J4 ,5 = 8.1 Hz, J4 ,6 = J4 ,2 = 2.1 Hz,
H-40), 5.97 (2H, m, H-200, H-2000), 5.75 (2H, m, H-300, H-3000),
4.81 (2H, m, H-100, H-1000), and 2.15–1.30 (12 protons of
cyclohexene).
0
0
0
0
0
0
4.1 | Synthesis of 3-cyclohexenyloxychromenones: A
general procedure for 1a
Compound 2c: Yield 0.225 g (50%), yellow semisolid;
vmax (cm−1) 1,640 (C=O); δH (CDCl3): 8.18 (1H, d,
J5,7 = 2.4 Hz, H-5), 7.52 (1H, dd, J7,5 = 2.4 Hz,
To 0.50 g (0.001 mol) of 3-hydroxychromenone and 2 g of
K2CO3 in dry acetone, 0.21 g (0.001 mol) of
3-bromocyclohex-1-ene was added. Then, the PTC,
Bu4N+I− (10 mg), was added and the reaction mixture was
refluxed for 4 hr. The resulting reaction mixture was poured
onto ice-cold water and neutralized with dil. HCl to obtain
the compound 1a. The compound 1a was purified by perco-
lation through a column of silica gel (100–200 mesh). Like-
wise, the other chromenones 1(b–c) and 2(a–c) were
synthesized.
0
0
J7,8 = 9.0 Hz, H-7), 7.48 (1H, dd, J6 ,4 = 1.8 Hz,
J6 ,5 = 8.4 Hz, H-60), 7.39 (1H, d{t}, J4 ,6 = 1.8 Hz,
0
0
0
0
J4 ,5 = J4 ,3 = 8.4 Hz, H-40), 7.34 (1H, d, J8,7 = 9.0 Hz, H-
0
0
0
0
0
0
0
0
0
0
8), 7.00 (1H, d{t}, J5 ,3 = 1.8 Hz, J5 ,4 = J5 ,6 = 8.4 Hz,
H-50), 6.95 (1H, dd, J3 ,5 = 1.8 Hz, J3 ,4 = 8.4 Hz, H-30),
5.94 (2H, m, H-200, H-2000), 5.69 (2H, m, H-300, H-3000), 4.79
(2H, m, H-100, H-1000), and 2.19–1.33 (12 protons of cyclo-
hexene rings).
0
0
0
0
Compound 1a: Yield 0.24 g (59%), light yellow semi-
solid; vmax (cm−1) 1,640.2 (C=O); δH (CDCl3) 8.26 (1H, d,
0
0
0
0
4.2 | Photolysis of 3-cyclohexenyloxychromenones: A
general procedure for 1a
J5,6 = 7.8 Hz, H-5), 8.14 (2H, d, J2 ,3 = J6 ,5 = 8.7 Hz, H-
20, H-60), 7.65 (1H, dt, J6,8 = 1.2 Hz, J6,7 = J6,5 = 8.7 Hz,
H-6), 7.52 (1H, dd, J8,6 = 1.2 Hz, J8,7 = 8.7 Hz, H-8), 7.38
(1H, 0dt, J7,5 = 01.2 Hz, J7,6 = J7,8 = 8.7 Hz, H-7), 7.01 (2H,
The compound 1a (50 mg) was irradiated for 90 min in dry
benzene (100.0 mL) using a pyrex-filtered light from a
125 W medium pressure mercury lamp under the N2 atmo-
sphere. The progress of the reaction was monitored by tlc.
The solvent was distilled to obtain a red gummy viscous
mass that was chromatographed over a column of silica gel
(100–200 mesh) packed in pet. ether-benzene (2:3). Elution
of the column gave starting compound 1a (20%, co-tlc &
mmp), a new compound 3a, and 3-hydroxychromenone 4a.
0
0
d, J3 ,2 = J5 ,6 = 8.7 Hz, H-30, H-50), 6.09 (2H, m, H-200,
H-2000), 5.86 (2H, m, H-300, H-3000), 4.91 (2H, m, H-100,
H-1000), and 2.08–1.48 (12 protons of cyclohexene rings).
Compound 1b: Yield 0.19 g (47%), yellow semisolid;
vmax (cm−1) 1,640 (C=O); δH (CDCl3) 8.27 (1H, d,
0
0
J5,6 = 7.8 Hz, H-5), 7.76 (1H, t, J2 ,4 = 2.1 Hz, H-20), 7.68
(2H, m, H-6, H-8), 7.54 (1H, d, J6 ,5 = 8.1 Hz, H-60), 7.39
0
0

KHANNA ET AL.
5
The other chromenones 1(b–c) and 2(a–c) were photolyzed
and processed by using this protocol. The chromenones 1c
and 2c did not furnish any photoproduct.
Compound 5a: Yield 50 mg (25%), brick red solid, mp
181–183ꢀC; vmax (cm−1) 1,625 (C=O); δH (CDCl3) 8.29
(1H, d, J8,10 = 2.4 Hz, H-8), 7.82 (1H, d, J1,2 = 8.4 Hz,
H-1), 7.59 (1H, dd, J10,11 = 8.7 Hz, J10,8 = 2.4 Hz, H-10),
7.51 (1H, d, J11,10 = 8.7 Hz, H-11), 6.99 (1H, dd,
J2,1 = 8.4 Hz, J2,4 = 2.4 Hz, H-2), 6.78 (1H, d,
J4,2 = 2.4 Hz, H-4), 6.30 (1H, m, H-200), 6.10-5.50 (3H, m,
H-20, H-30, H-100), 4.91 (1H, broad s/m, H-10), and 2.35–1.50
(12H, H-40, H-50, H-60, H-300, H-400, H-500). Anal. Calcd. For
C27H24O4: C, 78.62; H, 5.86; and O, 15.52. Found: C,
78.59; H, 5.81; and O, 15.48.
Compound 3a: Yield 50 mg (17%), brick red semisolid;
vmax (cm−1) 1,620 (C=O); δH (CDCl3) 8.28 (1H, d,
J8,9 = 8.7 Hz, H-8), 8.01(1H, d, J1,2 = 8.4 Hz, H-1), 7.66
(1H, dt, J9,11 = 1.5 Hz, J9,8 = J9,10 = 8.7 Hz, H-9), 7.54
(1H, dd, J11,9 = 1.5 Hz, J11,10 = 8.4 Hz, H-11), 7.40 (1H,
dt, J10,8 = 1.5 Hz, J10,9 = J10,11 = 8.7 Hz, H-10), 7.00 (1 H,
dd, J2,1 = 8.4 Hz, J2,4 = 2.6 Hz, H-2), 6.80 (1H, d,
J4,2 = 2.6 Hz, H-4), 6.35 (1H, m, H-200), 6.30-5.60 (3H, m,
H-20, H-30, H-100), 5.0 (1H, broad s/m, H-10), and 2.40–1.60
(12H, H-40, H-50, H-60, H-300, H-400, H-500). Anal. Calcd. For
C27H24O4: C, 78.62; H, 5.86; and O, 15.52. Found: C,
78.59; H, 5.81; and O, 15.48.
Compound 6a: Yield 21 mg (7%), yellow solid; mp
200–202ꢀC; vmax (cm−1) 3,279 (OH), 1,603.1 (C=O); δH
(CDCl3) 8.14 (2H, d, J2 , 3 = J6 ,5 = 9.0 Hz, H-20, H-60),
8.13 (1H, d, J5,7 = 2.4 Hz, H-5), 7.55 (1H, dd,
J7,8 = 9.0 Hz, J7,5 = 2.4 Hz, H-7), 7.47 (1H, d,
0
0
0
0
Compound 4a: Yield 20 mg (7%), yellow semisolid;
vmax (cm−1) 3,270 (OH), 1,600 (C=O); δH (CDCl3) 8.10
(1H, d, J5,6 = 9.0 Hz, H-5), 7.89 (2H, d,
0
0
0
0
J8,7 = 9.0 Hz, H-8), 6.99 (2 H, d, J3 ,2 = J5 ,6 = 9.0 Hz, H-
30, H-50), 5.96 (1H, td, J3 ,2 = 9.9 Hz, J3 ,4 = 3.6 Hz, H-
00 00
00 00
300), 5.83 (1H, dd, J2 ,3 = 9.9 Hz, Jvic = 6.0 Hz, H-200), 4.85
J2 ,3 = J6 ,5 = 8.5 Hz, H-20, H-60), 7.60 (1H, dt,
J6,8 = 1.5 Hz, J6,7 = J6,5 = 9.0 Hz, H-6), 7.50 (1H, dd,
J8,6 = 1.5 Hz, J8,7 = 9.0 Hz, H-8), 7.35 (1H, dd,
00 00
0
0
0
0
(1H, m, H-100), and 2.20-1.60 (6H, H-400, H-500, H-600). Anal.
Calcd. For C21H18O4: C, 75.43; H, 5.43; and O, 19.14.
Found: C, 75.41; H, 5.41; and O, 19.11.
J7,6 = J7,8 = 9.0
Hz,
H-7),
6.89
(2H,
d,
J3 ,2 = J5 ,6 = 8.5 Hz, H-30, H-50), 5.95 (1H, dt,
Compound 5b: Yield 50 mg (22%), brick red solid, mp
171–173ꢀC; vmax (cm−1) 1,645.4 (C=O); δH (CDCl3) 8.21
(1H, d, J8,10 = 2.4 Hz, H-8), 7.53 (1H, dd, J10,11 = 9.0 Hz,
J10,8 = 2.4 Hz, H-10), 7.45 (1H, d, J11,10 = 9.0 Hz, H-11),
7.33 (1H, d, J1,3 = 2.7 Hz, H-1), 7.05 (1H, d, J4,3 = 8.4 Hz,
H-4), 6.94 (1 H, dd, J3,4 = 8.4 Hz, J3,1 = 2.7 Hz, H-3),
6.20–5.80 (4H, m, H-20, H-30, H-100, H-200), 4.84 (1H, broad
s/m, H-10), and 2.25–1.30 (12H, H-40, H-50, H-60, H-300, H-
400, H-500). Anal. Calcd. For C27H23ClO4: C, 72.56; H, 5.19;
Cl, 7.93; and O, 14.32. Found: C, 72.52; H, 5.14; Cl, 7.87;
and O, 14.28.
0
0
0
0
J3 ,2 = 9.5 Hz, J3 ,4 = 3.5 Hz, H-300), 5.80 (1H, dd,
00 00
00 00
J2 ,3 = 9.5 Hz, Jvic = 5.5 Hz, H-200), 4.80 (1H, m, H-100),
00 00
and 2.10-1.60 (6H, H-400, H-500, H-600). Anal. Calcd. For
C21H18O4: C, 75.43; H, 5.43; and O, 19.14. Found: C,
75.39; H, 5.38; and O, 19.08.
Compound 3b: Yield 45 mg (16%), red semisolid; vmax
(cm−1
)
1,630 (C=O); δH (CDCl3) 8.25 (1H, d,
J8,9 = 8.1 Hz, J8,10 = 2.4 Hz, H-8), 8.00 (1H, d,
J1,3 = 2.5 Hz, H-1), 7.68 (1H, d{t}, J9,11 = 2.4 Hz,
J9,8 = J9,10 = 8.1 Hz, H-9), 7.50 (1H, dd, J11,9 = 2.4 Hz,
J11,10 = 8.1 Hz, H-11), 7.45 (1H, d{t}, J10,8
= 2.4 Hz, J10,11 = J10,9 = 8.1 Hz, H-10), 6.90 (1H, dd,
J3,4 = 8.4 Hz, J3,1 = 2.5 Hz, H-3), 6.56 (1H, d,
J4,3 = 8.4 Hz, H-4), 6.10–5.70 (5H, m, H-20, H-30, H-100,
H-200, H-10), and 2.20–1.40 (12H, H-40, H-50, H-60, H-300, H-400,
H-500). Anal. Calcd. For C27H23ClO4: C, 72.56; H, 5.19; Cl,
7.93; and O, 14.32. Found: C, 72.52; H, 5.14; and O, 14.28.
Compound 4b: Yield 25 mg (12.5%), yellow semisolid;
vmax (cm−1) 3,250 (OH), 1,610 (C=O); δH (CDCl3) 8.05
Compound 6b: Yield 20 mg (7%), yellow solid; mp
168–171ꢀC; vmax (cm−1) 3,256.9 (OH), 1,610.4 (C=O); δH
(CDCl3) 8.15 (1H, d, J5,7 = 2.4 Hz, H-5), 7.73 (1H, dd,
J2 ,4 = J2 ,6 = 2.4 Hz, H-20), 7.58 (1H, dd, J7,8 = 9.0 Hz,
0
0
0
0
0
0
J7,5 = 2.4 Hz, H-7), 7.56 (1H, ddd, J6 ,5 = 8.4 Hz,
J6 ,4 = J6 ,2 = 2.4 Hz, H-60), 7.48 (1H, d, J8,7 = 9.0 Hz, H-
0
0
0
0
8), 7.37 (1H, d, J5 ,4 = J5 ,6 = 8.4 Hz, H-50), 6.99 (1H, ddd,
0
0
0
0
J4 ,5 = 8.4 Hz, J4 ,6 = J4 ,2 = 2.4 Hz, H-40), 6.91 (1H, s,
OH) 5.94 (1H, m, H-300), 5.84 (1H, m, H-200), 4.83 (1H, m,
H-100), and 2.20-1.60 (6H, H-400, H-500, H-600). Anal. Calcd.
For C21H17ClO4: C, 68.39; H, 4.65; Cl, 9.61; and O, 17.35.
Found: C, 68.32; H, 4.61; Cl, 9.57; and O, 17.33.
0
0
0
0
0
0
0
0
(1H, d, J5,6 = 7.8 Hz, H-5), 7.87 (1H, d, J2 ,4 = 2.4 Hz, H-
20), 7.61 (1H, dt, J6,8 = 1.5 Hz, J6,5 = J6,7 = 7.8 Hz, H-6),
7.55 (1H, dd, J8,6 = 1.5 Hz, J8,7 = 9.0 Hz, H-8), 7.50 (1H,
dd, J6 ,5 = 8.1 Hz, J6 ,4 = 2.4 Hz, H-60), 7.36 (1H, t,
0
0
0
0
J5 ,6 = J5 ,4 = 8.1 Hz, H-50), 7.34 (1H, d{t}, J7,5 = 1.5 Hz,
0
0
0
0
0
0
J7,8 = J7,6 = 9.0 Hz, H-7), 6.95 (1H, ddd, J4 ,5 = 8.2 Hz,
ACKNOWLEDGMENTS
J4 ,6 = J4 ,2 = 2.4 Hz, H-40), 5.94 (1H, m, H-300), 5.82 (1H,
m, H-200), 4.82 (1H, m, H-100), and 2.15-1.55 (6H, m, H-400,
H-500, H-600). Anal. Calcd. For C21H17ClO4: C, 68.39; H,
4.65; Cl, 9.61; and O, 17.35. Found: C, 68.32; H, 4.60; Cl,
9.57; and O, 17.31.
0
0
0
0
Two of the authors wish to express their gratitude to the Bio-
technology Industry Research Assistance Council (BIRAC),
New Delhi, and Maharishi Markandeshwar (Deemed to be
University) (Radhika Khanna, Post doc BIRAC innovation
fellow) and the University Grants Commission (UGC), New
Delhi (Aarti Dalal, SRF), for financial support of this work.

6
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ORCID
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https://orcid.org/0000-0002-9889-6452
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How to cite this article: Khanna R, Dalal A,
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