First concise total synthesis of 5-epi-prelactone B

Article abstract of DOI:10.1080/00397910801914194

First short total synthesis of 5-epi-prelactone B has been achieved involving Sharpless asymmetric epoxidation and intramolecular hydride transfer reaction for formation of the aldol product by nonaldol chemistry as the key steps. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397910801914194

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First Concise Total Synthesis of
5‐Epi‐prelactone B
P. Srihari a , K. Ravindar a , R. Somaiah a & J. S. Yadav a
a Organic Division I, Indian Institute of Chemical Technology, Hyderabad,
India
Published online: 25 Apr 2008.
To cite this article: P. Srihari , K. Ravindar , R. Somaiah & J. S. Yadav (2008) First Concise Total Synthesis
of 5‐Epi‐prelactone B, Synthetic Communications: An International Journal for Rapid Communication of
Synthetic Organic Chemistry, 38:9, 1389-1397, DOI: 10.1080/00397910801914194
To link to this article: http://dx.doi.org/10.1080/00397910801914194
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Synthetic Communicationsw, 38: 1389–1397, 2008
Copyright # Taylor & Francis Group, LLC
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910801914194
First Concise Total Synthesis
of 5-Epi-prelactone B
P. Srihari, K. Ravindar, R. Somaiah, and J. S. Yadav
Organic Division I, Indian Institute of Chemical Technology,
Hyderabad, India
Abstract: First short total synthesis of 5-epi-prelactone B has been achieved involving
Sharpless asymmetric epoxidation and intramolecular hydride transfer reaction for
formation of the aldol product by nonaldol chemistry as the key steps.
Keywords: Aldol, d-lactones, prelactone B, Sharpless asymmetric epoxidation, Wittig
reaction
INTRODUCTION
d-Lactones, specifically b-hydroxy-d-lactones, are structural components of
many bioactive natural products. Prelactones[1–4] 4–7 isolated from various
polyketide macrolide-producing microorganisms are a subgroup of this class
of compounds and have received attained much attention because of their
structural motifs, which represent useful building blocks for the synthesis of
complex structures such as bafilomycins,[5,6] concanomycin,[7,8] hygrolidin,[9]
and compactin[10] (see Fig. 1).
Prelactone B was isolated from Streptomyces griseus[4] (strain Tu 2599
ana 18) and represents an early metabolite in the biosynthesis of polyketide
antibiotics. It has been used as a standard for investigations concerning the
mechanism of polyketide synthase (PKS). Because of the importance of this
class of compound, several syntheses of prelactone B[11] and epi-prelac-
tones[12] have been well reported. As part of an academic program, we were
Received in India October 27, 2007
Address correspondence to P. Srihari, Organic Division I, Indian Institute of
Chemical Technology, Hyderabad 500007, India. E-mail: srihari@iict.res.in
1389

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P. Srihari et al.
Figure 1. Few biologically active compounds with b-hydroxy d-lactone motifs.
interested in the synthesis of compounds containing b-hydroxy-d-lactone
moieties and have investigated various strategies that lead to the development
of two different routes for the synthesis of b-hydroxy-d-lactones, resulting in
multigram synthesis of prelactone B[13] and total synthesis of prelactone B, C,
and V.[14] In continuation of our work on b-hydroxy-d-lactones, herein we
report the first total synthesis of 5-epi-prelactone B by employing Sharpless
asymmetric epoxidation and an intramolecular hydride transfer reaction to
get the aldol product 10 (by nonaldol chemistry) for the synthesis of 5-epi-
prelactone B as the key steps. Our retrosynthetic analysis is depicted in Fig. 2.
RESULTS AND DISCUSSION
The synthesis of 5-epi-prelactone starts with the commercially available isobu-
tyraldehyde, which was subjected to the Wittig reaction with (1-(ethoxycarbony-
l)ethyl)triphenylphosphonium bromide) to exclusively get the trans ester 11. The
ester 11, on reduction with DIBAL-H,[15] afforded allyl alcohol 12 and was then
subjected to Sharpless asymmetric epoxidation[16] with D(2)-diethyl tartarate
(DET), tert-butyl hydroperoxide (TBHP), and Ti(iPrO)4 to get the chiral epoxy
alcohol 13 in 90% yield with 96% ee. The epoxy alcohol was treated with
Figure 2. Retrosynthesis.

5-Epi-prelactone B
1391
Scheme 1.
TBSOTf in the presence of Hunig’s base for the intramolecular hydride tranfer
from the methylene group of the in situ formed silyl ether of the epoxy alcohol
to get the TBS protected aldehyde 10.[17] The resulting aldehyde 10 was
subjected to the Wittig reaction with (methoxycarbonylmethyl)triphenylpho-
sphonium bromide to afford the trans homologated product 14 in 85% yield.
The compound 14 was treated with DIBAL-H to reduce the conjugated ester
to allyl alcohol 15. The allyl alcohol 15, upon Sharpless asymmetric epoxida-
tion with L(þ)-DET, TBHP, and Ti(iPrO)4 in DCM at –30 8C, gave chiral
epoxy alcohol 9. The chiral epoxy alcohol, on treatment with sodium bis(2-
methoxyethoxy)aluminum hydride, underwent a one-pot epoxide opening
and also desilylation to afford the 1,3,5-triol 16 (Scheme 1). Selective
oxidation[18] of the primary alcohol with (diacetoxyiodo)benzene (BAIB) in
the presence of 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) afforded the
target molecule 5-epi-prelactone B. The stereochemistry of the product was
also reconfirmed by NMR studies from the coupling constant values.
CONCLUSION
In conclusion, an efficient short synthesis of 5-epi-prelactone B has been
described in an overall yield of 21% from nine steps. The synthetic strategy
applied is amenable for multigram scale synthesis and also provides access

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P. Srihari et al.
to other prelactones and their derivatives by maneuvering the substrates and
reagents. Studies to evaluate of their biological activity are currently under
progress.
EXPERIMENTAL
All the solvents were dried and distilled prior to use. Column chromatography
was performed using silica gel 60–120 mesh. IR spectra were recorded on a
Perkin-Elmer infrared spectrophotometer as KBr wafers, neat, or in CHCl3
1
as a thin film. H and 13C NMR were recorded on a Varian Gemini 200 or
Bruker Avance 300-MHz instrument using TMS as an internal standard.
Mass spectra were recorded on Micromass VG 7070H mass spectrometer for
electron impact (EI), VG Autospec mass spectrometer for fast atom bombard-
ment mass spectroscopy (FABMS), and micromass Quatro LC-triple quadru-
pole mass spectrometer for electron spray ionization (ESI) analysis. The
optical rotations were recorded on a Jasco DIP-360 digital polarimeter at 25 8C.
(E)-Ethyl 2,4-dimethylpent-2-enoate (11)
Ethoxycarbonylmethylenetriphenylphosphorane (19.6 g, 45 mmol) to the
mixture of the isobutyraldehyde (3.0 g, 41 mmol) in CH2Cl2 (50 mL) was
added at 0 8C, and the mixture was allowed to stirr for 2 h at room tempera-
ture. Then CH2Cl2 was removed under reduced pressure; this crude product
was purified by column chromatography to afford the pure ester as a
colorless oil. Yield 4.5 g (70%); Rf 0.80 (EtOAc/hexane 10:90); IR (KBr):
1
v
max, 2922, 2852, 1738, 1461, 1375, 1098, 759 cm21. H NMR (300 MHz,
CDCl3): d 6.51 (d, 1H, J ¼ 9.0 Hz), 4.16 (q, 2H, J ¼7.0, 14.3 Hz), 2.66–
2.56 (m, 1H), 1.81 (s, 3H, J ¼ 1.0 Hz), 1.30 (t, 3H, J ¼ 7.0 Hz), 1.03
(d, 6H, J ¼ 7.0 Hz). 13C NMR (75 MHz, CDCl3): d 168.1, 148.3, 125.7,
60.49, 28.0, 22.0, 14.4, 12.3. EIMS: 157 [Mþ H]þ.
(E)-2,4-Dimethylpent-2-en-1-ol (12)
A solution of ester 11 (2.5 g, 16.8 mmol) in CH2Cl2 (100 mL) was treated with
DIBAL-H [28% (w/v) in toluene, 35.2 mL, 35 mmol] in a dropwise fashion at
0 8C. After stirring for 2 h at 0 8C, a saturated solution of aqueous potassium
sodium tartarate (50 mL) was added, and the mixture was extracted with Et2O
(3 ꢀ 25 mL). The combined organic layers were washed with brine, dried
(Na2SO4), filtered, and concentrated. The crude product was purified by
column chromatography to afford alcohol 12 as colorless oil. Yield 1.46 g
(80%); Rf 0.60 [EtOAc/hexane 10:90]; IR (KBr): vmax, 3421, 2922, 2852,
1
1735, 1627, 1461, 787 cm21; H NMR (300 MHz, CDCl3): d 5.19–5.23

5-Epi-prelactone B
1393
(d, 1H, J ¼ 9.0 Hz), 3.93 (s, 2H), 2.59–2.46 (m, 1H), 1.66 (s, 3H), 0.95 (d, 6H,
J ¼7.0 Hz); 13C NMR (75 MHz, CDCl3): d 134.2, 132.5, 69.0, 26.9, 22.8,
13.7; EIMS: 115 [Mþ H]þ.
((2R,3R)-3-Isopropyl-2-methyloxiran-2-yl)methanol (13)
˚
D-(2)-diethyltartarate (2.9 mL, 17 mmol) was added to a suspension of 4 A
MS (2 g) in 100 mL of CH2Cl2 followed by addition of Ti(i-PrO)4
(4.14 mL, 13 mmol) at 230 8C. The suspension was stirred at 230 8C for
30 min. A solution of allyl alcohol 12 (2.0 g, 17 mmol) was added
dropwise, The mixture was stirred at 230 8C for 1 h, then tert-butylhydroper-
oxide (TBHP, 2.32 mL, 24 mmol) was added dropwise. The resulting mixture
was stirred for 1 h at 230 8C, then warmed to 0 8C and poured into cooled
(0 8C) Fe2SO4 (38.0 g) and tartaric acid (11.0 g) in water (180 mL). The
resulting mixture was stirred for 15 min, and the aqueous phase was
saturated with solid NaCl and extracted with CH2Cl2 (5 ꢀ 50 ml).
Emulsions formed in some of the extractions were dispersed by filtration
through Celitew. The organic phases were combined and dried over
Na2SO4, filtered through Celite, concentrated under reduced pressure, and
purified by column chromatography to afford epoxy alcohol 13 as colorless
oil. Yield 2.05 g (90%); Rf 0.40 (EtOAc/hexane 20:80); [a]2D5 þ15.9 (c 1.0
CHCl3); IR (KBr): vmax 3443, 3923, 2853, 1626, 1460, 1383, 1083 cm21
;
1H NMR (300 MHz, CDCl3): d 3.63 (dd, 1H, J ¼ 12.0, 4.5 Hz), 3.51 (dd,
1H, J ¼ 12.0, 8.3 Hz), 2.65 (d, 1H, J ¼ 9.8 Hz), 1.99 (dd, 1H, J ¼ 8.3,
5.2 Hz), 1.54 (m, 1H), 1.29 (s, 3H), 1.10 (d, 3H, J ¼ 6.7 Hz), 0.95 (d, 3H,
J ¼ 6.7 Hz); 13C NMR (50 MHz, CDCl3): d 65.9, 65.5, 61.5, 27.5, 20.0,
18.3, 13.9; HRMS calcd. for C7H14O2Na; 153.0891; found: 153.0896.
(2S,3R)-3-(tert-Butyldimethylsilyloxy)-2,4-dimethylpentanal (10)
A solution of epoxy alcohol 13 (2.0 g, 15 mmol) and N,N-diisopropylethyl
amine (3.66 mL, 21 mmol) in CH2Cl2 was added to a cooled (240 8C) sus-
˚
pension of 4 A MS (2.5 g) in 100 mL of CH2Cl2. Then tert-butyldimethyl
trifluoromethane sulfonate (TBSOTf, 4.6 mL, 99 mmol) was added
dropwise over 15 min. The resulting solution was stirred for 1 h at 240 8C,
then quenched by addition of pH 7.0 buffer (25 mL) and allowed to warm
to room temperature. The mixture was diluted with pentane, and the phases
were separated. The organic phases were washed with saturated copper(II)
sulfate two times and brine, then dried over Na2SO4, filtered through Celite,
and concentrated under reduced pressure to give the aldehyde 10 as clear
yellow oil. Yield 3.19 g (85%); Rf 0.60 (EtOAc/Hexane 10:90); [a]D25
þ39.5 (c 1.30 CH2Cl2); IR (KBr): vmax, 2960, 2933, 2884, 2860, 1727,
1
1473, 1464, 1254, 1141, 1103, 1048, 1030, 1006, 837, 775, 667; H NMR

1394
P. Srihari et al.
(300 MHz, CDCl3) d 9.78 (d, 1H, J ¼ 0.7 Hz), 3.90 (dd, 1H, J ¼ 5.4, 3.8 Hz),
2.50 (m, 1H), 1.81 (m, 1H), 1.09 (d, 3H, J ¼ 7.1 Hz), 0.92 (d, 3H, J ¼ 6.9 Hz),
0.89 (d, 3H, J ¼ 6.8 Hz), 0.88 (s, 9H), 0.07 (s, 3H), 0.01 (s, 3H); 13C NMR
(75 MHz, CDCl3): d 205.4, 76.4, 50.6, 32.2, 29.7, 25.9, 19.7, 18.2, 8.6,
24.0, 24.2; HRMS: calcd. for C9H19O2Si (Mþ-C4H9) 187.1154; found:
187.1151.
(4R,5R,E)-Methyl-5-(tert-butyldimethylsilyloxy)-4,6-dimethylhept-
2-enoate (14)
A mixture of aldehyde 10 (2.5 g, 10 mmol) and methyl(triphenylphosphorany-
lidine)acetate (3.82 g, 11 mmol) in 50 mL of dry CH3CN was heated to reflux
for 18 h. The mixture was concentrated, diluted with 50 ml of CH2Cl2 and
80 mL of hexane, and filtered through a Celite pad to remove the polar impu-
rities. The solution was removed under reduced pressure and then purified by
column chromatography to afford the pure ester 14 as a colorless oil. Yield
2.61 g (85%); Rf 0.80 (EtOAc/hexane 10:90); [a]2D5 þ34.08 (c 1.50
CH2Cl2); IR (KBr): vmax, 2957, 2920, 2856, 1726, 1658, 1435, 1332, 1251,
1
1178, 1060, 837, 772 cm21; H NMR (300 MHz, CDCl3): d 7.01 (dd, 1H,
J ¼ 15.7, 7.8 Hz), 5.77 (dd, 1H, J ¼ 15.7, 1.3 Hz), 3.70 (s, 3H), 3.36 (t, 1H,
J ¼ 4.8 Hz), 2.48 (m, 1H), 1.71 (m, 1H), 1.03 (d, 3H, J ¼ 6.8 Hz), 0.89
(s, 9H), 0.86 (d, 3H, J ¼ 5.7 Hz), 0.85 (d, 3H, J ¼ 6.7 Hz), 0.03 (s, 3H),
0.01 (s, 3H); 13C NMR (75 MHz, CDCl3): d 167.2, 153.2, 119.7, 80.0, 51.3,
40.9, 32.0, 26.1, 20.3, 18.4, 17.5, 15.1, 23.7, 23.8; HRMS m/z calcd. for
C12H23O3Si (Mþ-C4H9) 243.1416; found: 243.1412.
(4R,5R,E)-5-(tert-Butyldimethylsilyloxy)-4,6-dimethylhept-
2-en-1-ol (15)
A solution of ester 14 (2.5 g, 8.3 mmol) in CH2Cl2 (100 mL) was treated with
DIBAL-H (1.0 M in hexane 18.3 mL, 18 mmol) in a dropwise fashion at
278 8C. After stirring for 2 h at 278 8C, a saturated solution of aqueous
potassium sodium tartarate (50 mL) was added and extracted with Et2O
(3 ꢀ 25 mL). The combined organic layers were washed with brine, dried
(Na2SO4), filtered, and concentrated. The crude product was purified by
column chromatography to afford alcohol 15 as a colorless oil; yield 1.46 g
(80%); Rf 0.40 (EtOAc/hexane 10:90); yield 1.92 g (85%); [a]2D5 þ10.68 (c
0.5 CHCl3); IR (KBr): vmax, 3445, 2921, 2862, 1729, 1629, 1459, 1280,
1
1117 cm21; H NMR (300 MHz, CDCl3): d 5.71–5.48 (m, 2H), 4.11–4.0
(m, 2H), 3.29–3.24 (m, 1H), 2.41–2.29 (m, 1H), 1.82–1.66 (m, 1H), 0.98
(d, 3H, J ¼ 6.7 Hz), 0.93–0.83 (m, 15H), 0.04 (s, 3H), 0.03 (s, 3H); 13C
NMR (75 MHz, CDCl3): d 137.5, 127.8, 81.0, 64.2, 40.8, 31.9, 26.4, 20.7,
17.8, 16.2, 23.3, 23.5; ESIMS: 273 [Mþ H]þ.

5-Epi-prelactone B
1395
((2S,3S)-3-(2R,3R)-3-(tert-Butyldimethylsilyloxy)-4-methylpentan-
2-yl)oxiran-2-yl)methanol (9)
˚
L-(þ)-diethyltartarate (1.25 mL, 7.3 mmol) was added to a suspension of 4 A
MS (2.5 g) in 100 mL of CH2Cl2 followed by addition of Ti(i-PrO)4 (1.78 mL,
5.9 mmol) at 230 8C. The suspension was stirred at 230 8C for 30 min. A
solution of allyl alcohol 15 (2.0 g, 7.3 mmol) was added dropwise; the
resulting mixture was stirred for 1 h at 230 8C. Then tert-butyl hydro
peroxide (TBHP, 1.0 mL, 10 mmol) was added dropwise. The mixture was
stirred at 230 8C for 1 h, then warmed to 0 8C and poured into a precooled
(0 8C) solution of Fe2SO4 (38.0 g) and tartaric acid (11.0 g) in water
(180 mL). The resulting mixture was stirred for 15 min, and the aqueous phase
was saturated with solid NaCl and extracted with CH2Cl2 (5 ꢀ 50 mL). The
organic phases were dried over Na2SO4, filtered through Celite, concentrated
under reduced pressure, and purified by column chromatography to afford
epoxy alcohol 9 as colorless oil. Yield 2.05 g (90%); Rf 0.40 (EtOAc/hexane
20:80); [a]2D5 216.608 (c 2.0 CHCl3); IR (KBr): vmax, 3442, 3921, 2852, 1625,
1462, 1379, 1081 cm21 1H NMR (300 MHz, CDCl3): d 3.87 (dd, 1H,
;
J ¼ 12.8, 4.5), 3.60 (dd, 1H, J ¼ 12.0, 4.50 Hz), 3.64–3.50 (m, 2H), 2.90–
2.82 (m, 2H), 1.85–1.70 (m, 1H), 1.57–1.45 (m, 1H), 1.05–0.82 (m, 18H),
0.08 (s, 3H), 0.07 (s, 3H); 13C NMR (75 MHz, CDCl3): d 77.8, 61.8, 58.7,
58.4, 39.0, 32.2, 26.1, 19.5, 18.8, 10.7, 23.7, 24.1; ESIMS: 289 [Mþ H]þ.
(3R,4R,5R)-4,6-Dimethylheptane-1,3,5-triol (16)
A solution of epoxy alcohol 9 (2.0 g, 6.9 mmol) in THF (100 mL) was treated
with Red-Al [65% (w/v) in toluene, 9.2 mL, 20.8 mmol] in a dropwise fashion
at 210 8C. After stirring for 8 h at 210 8C, a saturated solution of aqueous
potassium sodium tartarate (40 mL) was added, and the mixture was
extracted with Et2O (3 ꢀ 25 mL). The combined organic layers were washed
with brine, dried (Na2SO4), filtered, and concentrated. The crude product was
purified by column chromatography to afford triol 16 as a colorless oil; yield
1.03 g (85%); Rf 0.15 (EtOAc/hexane 50:50); yield 1.92 g (85%); [a]D25
21.408 (c 1.25 CHCl3); IR (KBr): vmax, 3475, 2966, 2920, 1460, 1272,
1010 cm21 1H NMR (300 MHz, CDCl3): d 4.16 (br s, 1H), 3.94–3.76
;
(m, 3H), 3.57–3.49 (m, 1H), 3.35 (br s, 2H), 1.94–1.80 (m, 1H), 1.72–1.57
(m, 2H), 1.28–1.22 (m, 1H), 1.01 (d, 3H, J ¼ 6.4 Hz), 0.98 (d, 3H,
J ¼ 6.9 Hz), 0.81 (d, 3H, J ¼ 6.8 Hz); 13C NMR (75 MHz, CDCl3): d 80.1,
74.7, 62.7, 39.1, 36.8, 31.4, 19.9, 19.0, 10.4; ESIMS: 177 [Mþ H]þ.
(4R,5R,6R)-4-Hydroxy-6-isopropyl-5-methyl-tetrahydropyran-
2-one (8)
Bis-acetoxyiodobenzene (BAIB, 7.32 g, 22.7 mmol) and 2,2,6,6-tetramethyl-
piperidinooxy (TEMPO, 0.16 g, 1.0 mmol) were added sequentially to the

1396
P. Srihari et al.
stirred solution of triol 16 (1.0 g, 5.6 mmol) in CH2Cl2 (10 mL) at room temp-
erature. After stirring for 3.0 h, saturated aqueous Na2S2O3 and Et2O (25 mL)
were added. The separated organic phase was washed with saturated aqueous
NaHCO3 and brine, dried over anhydrous Na2SO4, filtered, and concentrated
under reduced pressure. The residue was purified by column chromatography
to provide lactone 8 as a colorless viscous oil; yield 0.8 g (90%); Rf 0.50
(EtOAc/hexane 50:50); yield 1.92 g (85%); [a]2D0 ¼ þ48.0 (c 1.75 CHCl3);
1
IR (KBr): vmax 3473, 2970, 2924, 1715, 1463, 1272, 1006 cm21; H NMR
(300 MHz, CDCl3): d 4.15 (m, 1H), 3.69 (dd, 1H, J ¼ 10.2, 2.2 Hz), 2.80
(dd, 1H, J ¼ 18.1, 7.1 Hz), 2.40 (dd, 1H, J ¼ 18.1, 10.5 Hz), 2.25 (m, 1H),
1.92 (m, 1H), 1.10 (d, 3H, J ¼ 6.4 Hz), 0.92 (d, 6H, J ¼7.1 Hz); 13C NMR
(50 MHz, CDCl3): d 171.13, 86.63, 67.33, 35.34, 34.89, 29.72, 20.07,
18.13, 3.73; ESIMS: 173 [Mþ þ H]. HRMS: calcd. for C9H16O3Na [m/z]:
195.0997; found: 195.1000.
ACKNOWLEDGMENTS
Two of us (K. R.) and (R. S.) thank Council of Scientific and Industrial
Research (CSIR), New Delhi, for financial assistance.
REFERENCES
1. Cortes, J.; Wiesman, K. E. H.; Roberts, G. A.; Brown, M. J. B.; Staunton, J.;
Leadlay, P. F. Science 1995, 268, 1487–1489.
2. Kao, C. M.; Luo, G.; Katz, L.; Cane, D. E.; Khosla, C. J. Am. Chem. Soc. 1994,
116, 11612–11613.
3. Gerlitz, M.; Hammann, P.; Thiericker, R.; Rohr, J. J. Org. Chem. 1992, 57,
4030–4033.
4. Bindseil, K. U.; Zeeck, A. Helv. Chim. Acta 1993, 76, 150–157.
5. Toshima, K.; Yamaguchi, H.; Jyojima, T.; Noguchi, Y.; Nakata, M.;
Matsumura, M. Tetrahedron Lett. 1996, 37, 1073–1076.
6. Corey, E. J.; Ponder, J. W. Tetrahedron Lett. 1984, 25, 4325–4328.
7. Toshima, K.; Jyojima, T.; Miyamoto, N.; Katohno, M.; Nakata, M.; Matsumura, S.
J. Org. Chem. 2001, 66, 1708–1715.
8. Kinashi, H.; Someno, K.; Sakaguchi, K.; Higashijima, T.; Miyazawa, T. Tetrahe-
dron Lett. 1981, 22, 3861–3864.
9. Makino, K.; Nakajima, N.; Hashimoto, S.; Yonemitsu, O. Tetrahedron Lett. 1996,
37, 9077–9080.
10. Rosen, T.; Taschner, M. J.; Heathcock, C. H. J. Org. Chem. 1984, 49, 3994–4003.
11. (a) Aggarwal, V. K.; Bae, I.; Lee, H. Y. Tetrahedron 2004, 60, 9725–9733;
(b) Dias, L. C.; Steil, L. J.; Vasconcelos, V. de A. Tetrahedron: Asymmetry
2004, 15, 147–150; (c) Pihko, P. M.; Erkkila, A. Tetrahedron Lett. 2003, 44,
7607–7609; (d) Chakraborty, T. K.; Tapadar, S. Tetrahedron Lett. 2003, 44,
2541–2543; (e) Fournier, L.; Gaudel-sin, A.; Kocienski, P. J.; Pons, J. M.
Synlett 2003, 2182–2184; (f) Hanefeld, U.; Hooper, A. M.; Staunton, J.

5-Epi-prelactone B
1397
Synthesis 1999, 38, 401–403; (g) Csaky, A. G.; Mba, M.; Plumet, J. Synlett 2003,
2092–2094.
12. Miyazawa, M.; Narantsetseg, M.; Yokoyama, H.; Yamaguchi, S.; Hirai, Y.
Heterocycles 2004, 63, 1017–1021; (b) Chandrasekhar, S.; Rambabu, C.; Jaya
Prakash, S. Tetrahedron Lett. 2006, 47, 1213–1215.
13. Yadav, J. S.; Bhaskar Reddy, K.; Sabitha, G. Tetrahedron Lett. 2004, 45,
6475–6476.
14. Yadav, J. S.; Sridhar Reddy, M.; Prasad, A. R. Tetrahedron Lett. 2005, 46,
2133–2136.
15. Kumar, P.; Bodas, M. S. J. Org. Chem. 2005, 70, 360–363.
16. Katsuki, T.; Sharpless, K. B. J. Am. Chem. Soc. 1980, 102, 5974–5976.
17. Jung, M. E.; D’Amico, D. C. J. Am. Chem. Soc. 1993, 115, 12208–12209.
18. Hansen, T. M.; Florence, G. J.; Lugo-Mas, P.; Chen, J.; Abrams, J. N.;
Forsyth, C. J. Tetrahedron Lett. 2003, 44, 57–59.