p-Methoxy Diphenylmethanol (MDPM), p-Phenyl Diphenylmethanol (PDPM), and p-Phenylphenyl Diphenylmethanol (PPDPM) - Protecting Groups for Alcohols - Protection and Deprotection

Article abstract of DOI:10.1081/SCC-120028367

Two new protecting groups viz. p-phenyl diphenylmethanol (PDPM) and p-phenylphenyl diphenylmethanol (PPDPM) were prepared and utilized along with p-methoxy diphenylmethanol (MDPM), for the protection of alcohols in the presence of Yb(OTf)₃. Deprotection of the above ethers was achieved using DDQ or CF₃COOH.

Full text of DOI:10.1081/SCC-120028367

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p‐Methoxy Diphenylmethanol (MDPM), p‐Phenyl
Diphenylmethanol (PDPM), and p‐Phenylphenyl
Diphenylmethanol (PPDPM)—Protecting Groups for
Alcohols—Protection and Deprotection
G. V. M. Sharma a , T. Rajendra Prasad a , Rakesh a & B. Srinivas a
a D‐211, Discovery Laboratory, Organic Chemistry Division III , Indian Institute of
Chemical Technology , Hyderabad, 500 007, India
Published online: 20 Aug 2006.
To cite this article: G. V. M. Sharma , T. Rajendra Prasad , Rakesh & B. Srinivas (2004) p‐Methoxy Diphenylmethanol
(MDPM), p‐Phenyl Diphenylmethanol (PDPM), and p‐Phenylphenyl Diphenylmethanol (PPDPM)—Protecting Groups for
Alcohols—Protection and Deprotection, Synthetic Communications: An International Journal for Rapid Communication of
Synthetic Organic Chemistry, 34:5, 941-950, DOI: 10.1081/SCC-120028367
To link to this article: http://dx.doi.org/10.1081/SCC-120028367
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SYNTHETIC COMMUNICATIONSw
Vol. 35, No. 5, pp. 941–950, 2004
p-Methoxy Diphenylmethanol (MDPM),
p-Phenyl Diphenylmethanol (PDPM),
and p-Phenylphenyl Diphenylmethanol
(PPDPM)—Protecting Groups for
Alcohols—Protection and Deprotection#
*
G. V. M. Sharma, T. Rajendra Prasad, Rakesh,
and B. Srinivas
D-211, Discovery Laboratory, Organic Chemistry Division III, Indian
Institute of Chemical Technology, Hyderabad, India
ABSTRACT
Two new protecting groups viz. p-phenyl diphenylmethanol (PDPM) and
p-phenylphenyl diphenylmethanol (PPDPM) were prepared and utilized
along with p-methoxy diphenylmethanol (MDPM), for the protection of
alcohols in the presence of Yb(OTf)3. Deprotection of the above ethers
was achieved using DDQ or CF3COOH.
Key Words: DPM; Alcohol; Protection; Yb(OTf)3.
#IICT Communication Number: 021001.
*
Correspondence: G. V. M. Sharma, D-211, Discovery Laboratory, Organic Chemistry
Division III, Indian Institute of Chemical Technology, Hyderabad 500 007, India;
E-mail: esmvee@iict.ap.nic.in.
941
DOI: 10.1081/SCC-120028367
0039-7911 (Print); 1532-2432 (Online)
www.dekker.com
Copyright # 2004 by Marcel Dekker, Inc.

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942
Sharma et al.
Development of new and mild reactions and reagents[1] for the protection
of functional groups is of paramount research in the area of synthetic organic
chemistry. A total synthesis of complex natural product always is benefited by
mild reagents and efficient protocols for the protection as well as deprotection.
Inspite, still there is an urge for new and specific protecting groups to realize
the successful overall operation of the total synthesis. Of the several protecting
groups for alcohol, benzylic groups such as triphenylmethyl (Tr), diphenyl-
methyl (DPM), benzyl (Bn), p-methoxy and p-phenyl benzyl (PMB and PPB)
etc. enjoy a widespread appreciation, especially the PMB and PPB with
oxidatively[2,3] labile groups. Hence, in this class of protecting groups, altering
the reactivities of the existing protecting groups to the diversified new pro-
tecting groups in order to show specificity in their mode of introduction and
removal is very essential. In continuation of our efforts in the area of masking/
unmasking of functional groups[4–11] herein, we report three new reagents viz.
p-methoxy diphenylmethanol (MDPM-1), p-phenyl diphenylmethanol
(PDPM-2) and p-phenylphenyl diphenylmethanol (PPDPM-3) for the
protection of alcohols (Equation).
The required new reagents 1, 2, and 3 were prepared from commercially
available aldehydes 4 and 5. Accordingly, 4 on reaction with PhMgBr (Sch. 1)
Scheme 1.

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Protecting Groups for Alcohols
943
Table 1. Protection of alcohols and deprotection of ethers.
Protection of
alcohols
Deprotection of
ethers
S.
No
Substrate
Product
Time Yield (%) Time Yield (%)
1
C8H17OH
7
C8H17OR
7a R ¼ A
7b R ¼ B
7c R ¼ C
30 min
10 hr
15 hr
84
77
76
12 hra
7.5 hr
1.5 hr
70
79
84
2
8
9
8a R ¼ A
8b R ¼ B
40 min
7 hr
65
79
12 hra
7 hr
75
82
3
9a R ¼ A
9b R ¼ B
9c R ¼ C
40 min
6 hr
15 hr
81
62
78
—
5 hr
2 hr
—
77
78
4
5
10
11
10a R ¼ A
10b R ¼ B
45 min
9 hr
76
72
—
7 hr
—
75
11a R ¼ A
11b R ¼ B
11c R ¼ C
30 min
5 hr
12 hr
76
85
76
—
7 hr
3 hr
—
83
82
6
12
12a R ¼ A; R0 ¼ H 40 min
59
19
62
62
—
—
—
—
73
72
12a0 R ¼ R0 ¼ A
45 min
12b R ¼ B; R0 ¼ H 10 hr
8 hr
2.5 hr
12c R ¼ C; R0 ¼ H 16 hr
7
13
13a R ¼ A
45 min
80
—
—
(continued)

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944
Sharma et al.
Table 1. Continued.
Protection of
alcohols
Deprotection of
ethers
S.
No
Substrate
Product
Time Yield (%) Time Yield (%)
8
9
14
14a R ¼ B
14b R ¼ C
11.5 hr
11 hr
80
79
7 hr
1.25 hr
82
85
15 R ¼ THP
16 R ¼ TBS
17 R ¼ Ac
15a R ¼ THP; R0 ¼ B 8 hr
16a R ¼ TBS; R0 ¼ B 9 hr
82
81
84
78
5 hr
83
81
72
77
8.5 hr
6 hr
1.5 hr
17a R ¼ Ac; R0 ¼ B
8 hr
17b R ¼ Ac; R0 ¼ C 10 hr
aDeprotection with DDQ (10 mol%) and Mn(OAc)3 (3 eq).
gave the carbinol 1 (84%), while 5 gave 2 (82%). Further, oxidation of 2 with
PDC followed by treatment of 6 with PhMgBr afforded 3 (79%).
Our earlier experience with active benzylic carbinols amply demonstrated
that the protection can be achieved with the carbinols 1, 2, and 3 in the
presence of Lewis acids such as Yb(OTf)3. Accordingly, 7 (Table 1) was
treated with MDPM-1 and 10 mol% Yb(OTf)3 in CH2Cl2 at room temperature
for 30 min. to afford the corresponding MDPM ether 7a (84%). Similarly,
alcohol 8 on etherification with 1 and Yb(OTf)3 gave ether 8a (65%). In a
further study, to establish the generality protection was extended to different
alcohols such as sugar alcohols 9, 12, 13 and terpenes 10, 11 using 1 and
Yb(OTf)3 to give the ethers 9a to 13a in good yields. In the case of 1,3-diol 12,
the mono- and di-protected products were obtained in 59% and 19% yields,
respectively, while the 1,2-diol 13 gave 13a as an exclusive product in 80%
yield.
The deprotection of MDPM ethers was attempted under oxidative con-
ditions. Accordingly, 7a and 8a were treated (Table 1) with DDQ in CH2Cl2–
H2O (19 : 1) to successfully furnish the alcohols 7 (75%) and 8 (78%),
respectively. It is well documented in the literature that PMB group undergoes
cleavage under acidic conditions.[11] To check the stability of the MDPM ether
towards acid hydrolysis, 7a was treated independently with (a) 60% aq. AcOH
at 608C and (b) TFA (cat.) in CH2Cl2 at room temperature to give 7 in 4 hr and
1.5 hr respectively. Thus, it was amply indicated that MDPM ethers, like PMB

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Protecting Groups for Alcohols
945
ethers are labile to acids. Earlier, we have demonstrated p-phenylbenzyl (PPB)
group, unlike PMB, is not labile to acids. Hence, to avoid the acid hydrolysis,
encountered with the corresponding MDPM ethers, in the present study a new
reagent, p-phenyl diphenylmethanol (PDPM-2) was prepared and used for the
protection of alcohols.
Accordingly, alcohol 7 was subjected to reaction with 2 using 10 mol% of
Yb(OTf)3 in CH2Cl2 to afford the ether 7b (77%). Encouraged by the result,
the study was extended to other alcohols 7–12 and 14–17 to afford the
corresponding ethers as shown in the Table 1. The unsymmetrical diol 12 with
2 furnished 12b (62%) as an exclusive product unlike with the corresponding
MDPM alcohol 1. Similarly alcohols 15 and 16 having acid sensitive THP and
TBS groups also underwent facile protection with 2 to afford 15a (82%) and
16a (81%), respectively, while alcohol 17 having a base sensitive group gave
17a (84%).
As demonstrated earlier,[11] the p-phenyl group facilitates the removal of
the groups such as 2 under oxidative conditions. Hence, the thus made ethers
were subjected to DDQ mediated oxidative deprotection to afford the corres-
ponding alcohols as indicated in the Table 1.
In a further study, acid catalysed hydrolysis of 7b with (a) 60% aq.
AcOH at 608C and (b) catalytic TFA in CH2Cl2 at room temperature, even
after 24 hr, did not show any traces of hydrolyzed products, thus indicating,
unlike the MDPM ethers, the PDPM ethers are stable to the acidic
hydrolysis.
Similarly, the newly prepared trityl analogue, PPDPM-3, was also
successfully utilized for the protection of alcohols 7, 9, 11, 12, 14, and 17 as
indicated in Table 1. p-Phenyl group, as evidenced from the above study,
facilitates the removal of such groups under oxidative conditions, while it
would enhance the rate of acid catalyzed hydrolysis in PPDPM ethers. Indeed,
hydrolysis of 7c with CF3COOH (10 mol%) in CH2Cl2 gave 7 in 84% yield in
1.5 hr, while the corresponding trityl ether of 7 required 2.5 hr, thus indicating
the enhanced rate of hydrolysis for PDPM ethers over triyl ethers. Similarly
hydrolysis of 9c, 11c, 12c, 14b to 17b gave the respective alcohols very
efficiently in 1 to 3 hr time (Table 1).
Thus, in conclusion, in the present study, protection of alcohols is
achieved with MDPM 1 and newly prepared reagents PDPM 2 and PPDPM 3
alcohols under acid catalyzed conditions using Yb(OTf)3. Oxidative and acid
catalyzed deprotective methods were efficiently utilized for the deprotection
of MDPM, PDPM, and PPDPM ethers, wherein MDPM ethers were found to
be sensitive to the acid hydrolysis unlike PDPM ethers. Thus, the two new
reagents PDPM and PPDPM, with their inherent qualities for the protection
and deprotection under mild conditions could find immense use when
compared to the related existing reagents.

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946
Sharma et al.
GENERAL EXPERIMENTAL PROCEDURE
The 1H NMR spectra were recorded on Varian Gemini 200 MHz spectro-
meter using TMS as an internal standard. Mass spectra were recorded on a VG
micromass 70-70H mass spectrometer and IR spectra were recorded on
Nicolet FT IR-740.
Protection of Alcohols with 1, 2, and 3
A mixture of alcohol (1 mmol) and 1, 2, or 3 (1 mmol) was treated with
Yb(OTf)3 (0.1mmol) in CH2Cl2 (10 mL) at room temperature or reflux
temperature (for 3). The reaction mixtures were diluted with excess CH2Cl2
(20mL) and washed with sat. aq. NaHCO3 (10 mL). The organic layer was dried
(Na2SO4) and evaporated under reduced pressure. The crude residue was puri-
fied by column chromatography (Silicagel, hexane–EtOAc) to afford the ethers.
Deprotection of Ethers with DDQ
A mixture of MDPM or PDPM ether (1 mmol) and DDQ (1 mmol) was
stirred in CH2Cl2 (10 mL) at room temperature. The reaction mixture was
quenched with aq. NaHCO3 (10 mL) solution and diluted with excess CH2Cl2
(10 mL). The organic layer was dried (Na2SO4) and evaporated under reduced
pressure. The crude residue was purified was purified by column chroma-
tography (Silicagel, hexane–EtOAc) to afford the alcohols.
Deprotection with TFA
A mixture of PPDPM ether (1 mmol) and TFA (0.1 mmol) was stirred in
CH2Cl2 (10 mL) at room temperature. The reaction mixture was quenched
with aq. NaHCO3 (10 mL) solution and diluted with excess CH2Cl2 (10 mL).
The organic layer was dried (Na2SO4) and evaporated under reduced pressure.
The crude residue was purified was purified by column chromatography
(Silicagel, hexane–EtOAc) to afford the alcohols.
Spectral Data
7a: IR (neat): 700, 770, 1100, 1460, 2950 cm21 1H NMR (CDCl3,
;
200 MHz): d 0.92 (t, J ¼ 5.82, 16.4 Hz, 3H), 1.30 (s, 10H), 1.65 (t, J ¼ 8.32,
16.6 Hz, 2H), 3.45 (t, J ¼ 8.32, 16.6 Hz, 2H), 3.82 (s, 3H), 5.46 (s, 1H), 6.82

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Protecting Groups for Alcohols
947
(d, J ¼ 9.0 Hz, 2H), 7.15–7.40 (m, 7H); FABMS (m/z, %): 326 (Mþ, 26), 259
(15), 243 (100), 105 (40), 57 (30); analysis calcd. for C22H30O2: C, 80.94;
H, 9.26; found: C, 80.82; H, 9.18. 7b: IR (neat): 700, 760, 1100, 1480,
1
2940 cm21; H NMR (CDCl3, 200 MHz): d 0.90 (t, J ¼ 5.83, 16.6 Hz, 3H),
1.30 (s, 10H), 1.64 (t, J ¼ 8.33, 16.6 Hz, 2H), 3.45 (t, J ¼ 8.33, 16.6 Hz, 2H),
5.30 (s, 1H), 7.15–7.40 (m, 10H), 7.42–7.60 (m, 4H); FABMS (m/z, %): 259
(16), 243 (100), 105 (44), 91 (20), 57 (30); analysis calcd. for C27H32O:
C, 87.05; H, 8.66; found: C, 87.00; H, 8.52. 7c: IR (neat): 680, 750, 1040,
1
1450, 2900 cm21; H NMR (CDCl3, 200 MHz): d 0.09 (t, J ¼ 8.0, 16.0 Hz,
3H), 1.30 (s, 10H), 1.65 (t, J ¼ 6.4, 12.0 Hz, 2H), 3.08 (t, J ¼ 8.0, 16.0 Hz,
2H), 7.10–7.26 (m, 8H), 7.28–7.60 (m, 11H); FABMS (m/z, %): 319 (74),
259 (54), 241 (82), 183 (56), 105 (100); analysis calcd. for C33H36O: C, 88.35;
H, 8.09; found: C, 80.28; H, 8.00. 8a: IR (neat): 680, 750, 1040, 1450,
2950 cm21 1H NMR (CDCl3, 200 MHz): d 1.45–2.0 (m, 4H), 3.48
;
(t, J ¼ 6.75 Hz, 2H), 3.64 (t, J ¼ 6.75 Hz, 2H), 5.32 (s, 1H), 6.82
(d, J ¼ 9.0 Hz, 2H) 7.15–7.45 (m, 17H); FABMS (m/z, %): 452 (Mþ, 12),
213 (15), 197 (100), 137 (5), 55 (10); analysis calcd. for C31H32O3: C, 82.27;
H, 7.13; found: C, 82.19; H, 7.10. 8b: IR (neat): 700, 760, 1060, 1450,
2950 cm21 1H NMR (CDCl3, 200 MHz): d 1.46–2.02 (m, 4H), 3.48
;
(t, J ¼ 6.74 Hz, 2H), 3.66 (t, J ¼ 6.74 Hz, 2H), 5.32 (s, 1H), 5.54 (s, 1H), 6.81
(d, J ¼ 9.2 Hz, 2H), 7.15–7.42 (m, 17H), 7.45–7.60 (m, 4H); FABMS (m/z,
%): 213 (20), 197 (100), 137 (15), 55 (20); analysis calcd. for C36H34O2:
C, 86.71; H, 6.87; found: C, 86.68; H, 6.76. 9a: IR (neat): 720, 760, 1050,
1
1460, 2900 cm21; H NMR (CDCl3, 200 MHz): d 1.34, 1.40, 1.54 (3s, 12H,
4 CH3), 3.60 (t, 2H, J ¼ 6.75 Hz), 3.80 (s, 3H), 4.05 (m, 1H), 4.22–4.40
(m, 2H), 4.53–4.65 (m, 1H), 5.50 (s, 1H), 5.52 (d, J ¼ 4.95 Hz, 1H), 6.82
(d, J ¼ 8.65 Hz, 2H), 7.15–7.45 (m, 7H); FABMS: (m/z, %): 441 (Mþ, 215,
10), 197 (100), 91 (25), 69 (30), 57 (10); analysis calcd. for C26H32O7:
C, 71.34; H, 7.54; found: C, 71.23; H, 7.42. 9b: IR (KBr): 750, 1050, 1210,
1
1300, 2950 cm21; H NMR (CDCl3, 200 MHz): d 1.36 (s, 6H), 1.45 (s, 3H),
1.60 (s, 3H), 3.58–3.65 (m, 2H), 4.05 (t, J ¼ 8.0, 16.0 Hz, 1H), 4.25–4.38
(m, 2H), 4.60 (d, J ¼ 8.0 Hz, 1H), 5.50 (d, J ¼ 4.0 Hz, 2H), 7.20–7.40
(m, 10H), 7.44–7.60 (m, 4H); FABMS (m/z, %): 525 (Mþ, þ23), 259 (18),
243 (44), 241 (100), 91 (16); analysis calcd. for C31H34O6: C, 76.77; H, 7.25;
found: C, 76.59; H, 7.16. 9c: IR (KBr): 720, 1020, 1050, 1200, 2950 cm21
;
1H NMR (CDCl3, 200 MHz): d 1.38 (s, 6H), 1.45 (s, 3H), 1.60 (s, 3H), 3.30–
3.45 (m, 2H), 4.00 (t, J ¼ 8.0, 16.0 Hz, 1H), 4.25–4.40 (m, 2H), 4.60
(d, J ¼ 8.0 Hz, 1H), 5.50 (d, J ¼ 4.0 Hz, 1H), 7.20–7.42 (m, 8H), 7.46–7.62
(m, 11H); FABMS (m/z, %): 601 (Mþ, þ23, 24), 578 (Mþ, 20), 319 (100),
241 (24), 154 (30); analysis calcd. for C37H38O6: C, 79.14; H, 6.99; found:
C, 79.01; H, 6.85. 10a: IR (neat): 700, 740, 1050, 1450, 2950 cm21; 1H NMR
(CDCl3, 200 MHz): d 0.45 (d, J ¼ 3.2 Hz, 3H), 0.8–1.02 (m, 8H), 1.20–1.50

ORDER
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948
Sharma et al.
(m, 3H), 1.56–1.72 (m, 2H), 2.10–2.22 (m, 1H), 2.33 (d, J ¼ 10.2 Hz, 1H),
3.12 (dt, J ¼ 3.8, 10.2 Hz, 1H), 3.80 (s, 3H), 5.48 (s, 1H), 6.82 (d, J ¼ 9.0 Hz,
2H), 7.15–7.40 (m, 7H); FABMS: (m/z, %): 352 (Mþ, 30), 213 (10), 197
(100), 137 (10), 83 (15), 55 (10); analysis calcd. for C24H32O2: C, 81.77;
H, 9.15; found: C, 81.62; H, 9.00. 10b: IR (neat): 700, 760, 1060, 1450,
2950 cm21; 1H NMR (CDCl3, 300 MHz): d 0.45 (dd, J ¼ 10.3 Hz, 3H), 0.8–
1.02 (m, 8H), 1.20–1.42 (m, 3H), 1.56–1.70 (m, 2H), 2.10–2.25 (m, 1H),
2.30–2.45 (m, 1H), 3.10–3.22 (m, 1H), 5.54 (s, 1H), 7.15–7.42 (m, 10H),
7.45–7.60 (m, 4H); FABMS (m/z, %): 399 (Mþ, þ1, 10), 243 (100), 154 (10),
83 (14), 55 (12); analysis calcd. for C29H34O: C, 87.39; H, 8.60; found:
C, 87.23; H, 8.46. 11a: IR (neat): 680, 740, 1080, 1440, 2980 cm21; 1H NMR
(CDCl3, 200 MHz): d 1.40 (s, 3H), 1.50 (m, 9H), 2.12 (t, J ¼ 7.0 Hz, 2H), 3.45
(t, J ¼ 7.0 Hz, 2H), 3.78 (s, 3H), 5.25 (s, 1H), 5.38–5.48 (m, 1H), 6.80
(d, J ¼ 8.5 Hz, 2H), 7.15–7.40 (m, 7H); FABMS (m/z, %): 362 (Mþ, 15), 345
(30), 213 (5), 197 (100), 149 (10), 93 (10), 69 (12); analysis calcd. for
C25H30O2: C, 82.83; H, 8.34; found: C, 82.72; H, 8.23. 11b: IR (neat): 700,
760, 1100, 1500, 2880 cm21; 1H NMR (CDCl3, 200 MHz): d 1.42 (s, 3H), 1.50
(m, 9H), 2.12 (t, J ¼ 7.2 Hz, 2H), 3.44 (t, J ¼ 7.2 Hz, 2H), 5.52 (s, 1H), 5.38–
5.49 (m, 1H), 7.15–7.42 (m, 10H), 7.46–7.60 (m, 4H); FABMS (m/z, %), 431
(Mþ, þ23, 12), 259 (8), 243 (100), 105 (10), 91 (14); analysis calcd. for
C30H32O: C, 88.19; H, 7.89; found: C, 88.00; H, 7.72. 11c: IR (neat): 720, 760,
1
1040, 1500, 2900 cm21; H NMR (CDCl3, 200 MHz): d 1.42 (s, 3H), 1.50
(m, 9H), 2.11 (t, J ¼ 7.0 Hz, 2H), 3.42 (t, J ¼ 7.0 Hz, 2H), 5.36–5.49 (m, 1H),
7.20–7.42 (m, 8H), 7.46–7.62 (m, 11H); FABMS (m/z, %): 482 (10), 319
(100), 243 (16), 89 (64), 77 (60); analysis calcd. for C36H36O: C, 89.21;
H, 7.49; found: C, 89.13; H, 7.31. 12a: IR (neat): 700, 750, 1050, 1480,
1
2880 cm21; H NMR (CDCl3, 200 MHz): d 1.28, 1.43 (2s, 6H), 3.40 (dd,
J ¼ 3.5, 14.1 Hz, 1H), 3.78 (s, 3H), 3.85 (d, J ¼ 3.9 Hz, 2H), 4.15–4.30
(m, 2H), 4.45 (d, J ¼ 3.7 Hz, 1H), 5.40 (s, 1H), 5.90 (d, J ¼ 3.7 Hz, 1H), 6.80
(d, J ¼ 9.4 Hz, 2H), 7.10–7.40 (m, 7H); FABMS (m/z, %): 409 (Mþ, þ23,
12), 386 (Mþ, 25), 259 (70), 243 (100), 154 (65); analysis calcd. for C22H26O6:
C, 68.38; H, 6.78; found: C, 68.25; H, 6.68. 12a0: IR (neat): 680, 740, 1020,
1450, 2900 cm21; 1H NMR (CDCl3, 200 MHz): d 1.28, 1.45 (2s, 6H), 3.60–
3.85 (m, 1H), 3.9 (s, 6H), 4.10 (br.s, 2H), 4.50 (dd, J ¼ 3.0, 10.0 Hz, 1H), 5.30
(m, 1H), 5.45 (2s, 2H), 5.88 (m, 1H), 6.10–6.85 (m, 4H), 7.05–7.45 (m, 14H);
FABMS (m/z, %): 582 (Mþ, 5), 385 (16), 258 (62), 243 (100), 154 (30);
analysis calcd. for C36H38O7: C, 74.21; H, 6.57; found: C, 74.12; H, 6.45. 12b:
1
IR (neat): 700, 780, 1040, 2900, 3100 cm21; H NMR (CDCl3, 200 MHz):
d 1.30, 1.42 (2s, 6H), 3.34 (dd, J ¼ 8.69 Hz, 1H), 3.92 (d, J ¼ 4.34 Hz, 2H),
4.18–4.30 (m, 2H), 4.44 (d, J ¼ 4.34 Hz, 1H), 5.50 (s, 1H), 5.92
(d, J ¼ 4.34 Hz, 1H), 7.18–7.40 (m, 10H), 7.42–7.60 (m, 4H); FABMS
(m/z, %): 455 (Mþ, þ23, 10), 431 (Mþ, 21, 6), 259 (66), 243 (100), 154 (74);

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Protecting Groups for Alcohols
949
analysis calcd. for C27H28O5: C, 74.98; H, 6.53; found: C, 74.81; H, 6.41. 12c:
1
IR (neat): 700, 760, 1080, 1500, 2920 cm21; H NMR (CDCl3, 200 MHz):
d 1.25 (s, 3H), 1.45 (s, 3H), 3.38–3.64 (m, 2H), 4.20 (s, 2H), 4.44
(d, J ¼ 5.26 Hz, 1H), 5.94 (d, J ¼ 5.26 Hz, 1H), 7.20–7.40 (m, 8H), 7.46–
7.62 (m, 11H); FABMS (m/z, %): 509 (Mþ, þ1, 12), 319 (100), 259 (6), 91
(10), 55 (18); analysis calcd. for C33H32O5: C, 77.93; H, 6.34; found: C, 77.86;
H, 6.28. 13a: IR (neat): 680, 750, 1040, 1450, 2950 cm21; 1H NMR (CDCl3,
200 MHz): d 1.30, 1.50 (2s, 6H), 2.56–2.70 (br.s, 1H), 3.25 (ddd, J ¼ 4.7,
16.4, and 21.1 Hz, 1H), 3.42 (s, 3H), 3.75–3.85 (m, 4H), 4.0–4.20 (m, 2H),
4.52 (d, J ¼ 4.7 Hz, 1H), 5.40 (s, 1H), 5.82 (d, J ¼ 4.7 Hz, 1H), 6.83
(d, J ¼ 9.4 Hz, 2H), 7.15–7.40 (m, 7H); FABMS (m/z, %): 430 (Mþ, þ23,
10), 393 (10), 197 (100), 165 (10), 147 (15); analysis calcd. for C24H30O7: C,
66.96; H, 7.02; found: C, 66.84; H, 6.91. 14a: IR (neat): 710, 760, 1060, 1500,
2940 cm21; 1H NMR (CDCl3, 200 Mz): d 1.14 (d, J ¼ 8.2 Hz, 3H), 2.10 (br.s,
1H), 2.95–3.22 (m, 2H), 3.90–4.08 (m, 1H), 5.55 (s, 1H), 7.15–7.45 (m, 10H),
7.45–7.60 (m, 4H); FABMS (m/z, %): 318 (Mþ, 22), 214 (8), 165 (8), 105
(32), 55 (38); analysis calcd. for C22H22O2: C, 82.99; H, 6.96; found: C, 82.86;
H, 6.79. 14b: IR (neat): 700, 760, 1080, 1500, 2920 cm21; 1H NMR (CDCl3,
200 MHz): d 1.14 (d, J ¼ 8.3 Hz, 3H), 2.10 (br.s, 1H), 2.96–3.22 (m, 2H),
3.90–4.10 (m, 1H), 7.20–7.38 (m, 8H), 7.46–7.62 (m, 11H); FABMS
(m/z, %): 394 (Mþ, 5), 241 (10), 165 (8), 105 (20), 55 (30); analysis calcd. for
C28H26O2: C, 85.25; H, 6.64; found: C, 85.18; H, 6.49. 15a: IR (neat): 700,
780, 1240, 1750, 2950 cm21 1H NMR (CDCl3, 400 MHz): d 1.45–1.62
;
(m, 4H), 1.63–1.90 (m, 6H), 3.35–3.42 (m, 1H), 3.44–3.55 (m, 3H), 3.70–
3.88 (m, 2H), 4.58 (s, 1H), 5.38 (s, 1H), 7.15–7.42 (m, 10H), 7.46–7.58
(m, 4H); FABMS (m/z, %): 416 (Mþ, 8), 331 (10), 259 (20), 243 (100), 85
(55); analysis calcd. for C28H32O3: C, 80.73; H, 7.74; found: C, 80.61; H, 7.64.
16a: IR (neat): 760, 840, 1100, 1250, 2940 cm21 1H NMR (CDCl3,
;
400 MHz): d 0.05 (s, 6H), 0.95 (s, 9H), 1.55–1.65 (m, 4H), 3.56–3.70 (m, 4H),
5.40 (s, 1H), 7.14–7.40 (m, 10H), 7.46–7.56 (m, 4H); FABMS (m/z, %): 331
(12), 259 (14), 243 (100), 136 (30), 85 (52); analysis calcd. for C29H38O2Si:
C, 77.97; H, 8.57; found: C, 77.84; H, 8.50. 17a: IR (neat): 700, 1020, 1060,
1
1480, 2940 cm21; H NMR (CDCl3, 200 MHz): d 1.75 (t, J ¼ 8.2, 16.14 Hz,
4H), 2.02 (s, 3H), 3.50 (t, J ¼ 7.4, 14.8 Hz, 2H), 4.10 (t, J ¼ 7.4, 14.8 Hz, 2H),
5.30 (s, 1H), 7.12–7.40 (m, 10H), 7.45–7.60 (m, 4H); FABMS (m/z, %): 374
(Mþ, 6), 259 (14), 243 (100), 154 (14), 136 (24); analysis calcd. for C25H26O3:
C, 80.18; H, 7.00; found: C, 80.09; H, 6.86. 17b: IR (neat): 760, 1240, 1480,
1
1750, 3000 cm21; H NMR (CDCl3, 200 MHz): d 1.70 (t, J ¼ 8.0, 16.0 Hz,
4H), 2.00 (s, 3H), 3.20 (t, J ¼ 6.0, 12.0 Hz, 2H), 4.10 (t, J ¼ 6.0, 12.0 Hz, 2H),
7.22–7.40 (m, 8H), 7.45–7.65 (m, 11H); FABMS (m/z, %): 450 (Mþ, 24),
319 (100), 259 (16), 105 (42), 55 (25); analysis calcd. for C31H30O3: C, 82.64;
H, 6.71; found: C, 82.53; H, 6.68.

ORDER
REPRINTS
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Sharma et al.
ACKNOWLEDGMENTS
TRP and Rakesh are thankful to CSIR, New Delhi for financial support.
REFERENCES
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Received in the USA October 7, 2003

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