Direct	
  C7	
  Functionalization	
  of	
  Tryptophan.	
  Synthesis	
  of	
  Methyl	  (S)-­‐2-­‐((tert-­‐Butoxycarbonyl)amino)-­‐3-­‐(7-­‐(4,4,5,5-­‐tetramethyl-­‐1,3,2-­‐dioxaborolan-­‐2-­‐yl)-­‐1H-­‐indol-­‐3-­‐yl)propanoate.	
  Kazuma Amaike, Richard P. Loach, and Mohammad Movassaghi*

1,2

Department of Chemistry, Massachusetts Institute of Technology,
Cambridge, MA 02139, United States
Checked by Danilo Pereira de Sant’Ana and Richmond Sarpong

CO 2MeCO 2Me[Ir(cod)OMe] 2
dtbpy, THF, 60 °C;

NHBoc
+

HBPin

N
H
1

NHBoc

2

Pd(OAc) 2, AcOH
30 °C

BPin

N
H
3

Procedure	
  Methyl (S)-2-((tert-Butoxycarbonyl)amino)-3-(7-(4,4,5,5-tetramethyl-1,3,2dioxa-borolan-2-yl)-1H-indol-3-yl)propanoate (3). A flame-dried, 500-mL twonecked round-bottomed flask, equipped with a 3.5 cm football-shaped
magnetic stir bar and thermometer, is charged with N-Boc-L-tryptophan
methyl
ester
(1,
6.31
g,
19.8
mmol,
1.0 equiv),(1,5cyclooctadiene)(methoxy)iridium(I)
dimer
(328
mg,
0.500 mmol,
0.025 equiv), and 4,4'-di-tert-butyl-2,2'-bipyridine (266 mg, 0.991 mmol,
0.05 equiv) (Note 1). The flask is sealed with a rubber septum secured bycopper wire and placed under a nitrogen atmosphere after three successive
vacuum–argon cycles conducted slowly using a needle inlet through theseptum (Figure 1). Fresh anhydrous tetrahydrofuran (180 mL) (Note 2) isintroduced into the flask via a syringe to afford a dark brown solution.

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373

Published on the Web 12/15/2015©2015 Organic Syntheses, Inc.

Using a syringe, 4,4,5,5-tetramethyl-1,3,2-dioxaborolane (2, 14.4 mL,
99.1 mmol, 5.00 equiv) (Note 1) is added in a single portion, whereupon thesolution rapidly changes color from brown to dark red. This reaction
solution is stirred and maintained at 60 °C. After 13 h, TLC analysis
indicates complete consumption of starting material 1 (Notes 3 and 4).

Figure 1. Reaction Apparatus (photo provided by checkers)
The reaction solution is cooled to 23 ºC, and is concentrated under
reduced pressure (20 mmHg, 30 ºC) to afford a dark brown residue. Acetic
acid (20.0 mL) (Note 1) is slowly added to this residue to give a brownsolution, followed by addition of palladium(II) acetate (223 mg, 0.991 mmol,
0.05 equiv) (Note 1) in a single-portion. The mixture is stirred under anitrogen atmosphere at 30 °C for 12 h (Note 5), at which time TLC analysis
indicates complete consumption of the 2,7-diboronated intermediate. The
reaction mixture is then cooled to 23 ºC, filtered through Celite using a
glass-­‐‑sintered funnel (9 cm diameter, 4 cm height), and the filter cake isrinsed with ethyl acetate (3 × 150 mL). The filtrate is washed with saturated
aqueous sodium bicarbonate (500 mL), the layers are separated, and theaqueous layer is extracted with ethyl acetate (2 × 300 mL). The organic
layers are combined, dried over anhydrous sodium sulfate (15 g), filtered,and concentrated under reduced pressure (20 mmHg, 30 ºC). The resulting
brown residue is purified by flash column chromatography on silica gel(eluent: 5% acetone, 15% dichloromethane, 80% hexanes) (Note 6) toprovide a light yellow solid. The  solid  is  recrystallized  (Note  7)  to  afford  N-­‐‑

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Boc-­‐‑7-­‐‑boro-­‐‑L-­‐‑tryptophan   methyl   ester   3   as   a   white   powdery   solid   4.09–
4.29  g  (46.5–48.8%)  (Notes  8  and  9)  (Figure  2).    

Figure 2. Reaction Product 3 (photo provided by authors)

Notes	
  
1.

2.
3.

4.

N-Boc-L-Tryptophan methyl ester (99%) was used as purchased from
Chem-Impex International, Inc. 4,4,5,5-Tetramethyl-1,3,2-dioxaborolane(97%), (1,5-cyclooctadiene)(methoxy)iridium(I) dimer and 4,4'-di-tertbutyl-2,2'-bipyridine (98%) were used as purchased from Sigma Aldrich
Chemical Company, Inc. Palladium(II) acetate (98%) was used aspurchased from Strem Chemicals, Inc. Acetic acid, glacial (ACS grade)
was used as purchased from Fisher Scientific.
THF was purchased from Fisher Scientific and purified by the methodof Grubbs et al.3 under positive argon pressure.
Thin layer chromatography was performed using pre-coated (0.25 mm)
silica gel 60 F-254 plates purchased from SiliCycle (eluent: 5% acetone,
15% dichloromethane, 80% hexanes): Compound 1 Rf = 0.06 (CAM,
UV), Compound 3 Rf = 0.17 (CAM, UV), Compound 4 Rf = 0.26 (CAM,UV).
The intermediate N-Boc-2,7-diborotryptophan methyl ester (4, see
Scheme 2) could be isolated in ca. 88% yield as a white solid, by flash
column chromatography over silica gel (eluent: 5% acetone, 15%dichloromethane, 80% hexanes) (Note 6) of the crude mixture after thediboronation step (see Discussion section, Scheme 2). This productcontained trace impurities (<5%) but was not subjected to further

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5.

6.

7.

8.

chromatographic purification due to its sensitivity toward
C2 protodeboronation.
For
reference,data
for
N-Boc-2,7diborotryptophan methyl ester (4) is as follows: 1H NMR (500 MHz,CDCl3, 20 °C) δ: 1.33 (s, 9H), 1.39 (s, 18H), 1.40 (s, 6H), 3.33 (dd, J = 14.0,
10.0 Hz, 1H), 3.46 (dd, J = 14.0, 4.5 Hz, 1H), 3.70 (s, 3H), 4.36–4.28 (m,1H), 6.00 (d, J = 6.8 Hz, 1H), 7.11 (t, J = 7.2 Hz, 1H), 7.70 (d, J = 6.8 Hz,
1H), 7.77 (d, J = 8.0 Hz, 1H), 9.21 (br-s, 1H); 13C NMR (125 MHz, CDCl3,
20 °C) δ: 24.9, 25.2, 27.4, 28.2, 28.5, 52.3, 55.5, 79.4, 84.0, 84.6, 119.4, 123.1,
123.2, 127.0, 131.9, 143.1, 155.9, 173.7; FTIR (neat) cm–1: 3451 (br-s), 2979(s), 1751 (s), 1718 (s), 1596 (m), 1558 (s), 1436 (m), 1368 (m), 1293 (s), 1167(m), 1135 (s), 1050 (m), 851 (m); HRMS (ESI, TOF) (m/z) calc’d for
C29H44B2N2O8Na [M+Na]+: 593.3202, found: 593.3204; mp 105–106 °C;
Longer exposure to these protodeboronation conditions led to isolationof trace amounts (<5%) of N-Boc-L-tryptophan methyl ester (1),resulting from proto-deboronation of product 3.
Flash column chromatography (9.0 cm diameter, 17 cm height) was
performed using silica gel (60-Å pore size, 40–63 µm, standard grade,
Zeochem). The residue was loaded using dichloromethane (15 mL).
After 500 mL of initial elution, fraction collection (50 mL fractions) is
begun, and elution is continued with 2.7 L of eluent (5% acetone, 15%dichloromethane, 80% hexanes). The compound 3 is obtained in
fractions 21-54.
The   chromatographed   product   was   poured   into   a   125   mL   Erlenmeyer  flask   and   30   mL   of   hexanes/chloroform   (3:1)   was   added.   The   mixture  was   heated   to   its   boiling   point   (70   °C),   and   5   mL   portions   of  hexanes/chloroform  (3:1)  were  added  until  the  total  volume  was  55  mL  (the   solid   was   not   completely   dissolved).   The   mixture   was   cooled   to  23  °C,  capped  and  left  to  stand  for  13  h,  then  placed  in  a  fridge  at  4  °C  for  48  h.  The  recrystallized  solid  was  then  filtered  with  a  glass-­‐‑sintered  funnel,  washing  3  times  with  cooled  hexanes.
The analytical data for tryptophan derivative 3 is as follows: 1H NMRNMR  (500  MHz,  CDCl3)  δ:  1.39  (s,  12H),  1.43  (s,  9H),  3.30  (d,  J  =  5.4  Hz,  1H   ),   3.67   (s,   3H),   4.63   (dt,   J   =   8.5,   5.3   Hz,   1H)   5.06   (d,   J  =   8.2   Hz,   1H),  7.06  (s,   1H),   7.13   (t,   J  =   7.5   Hz,   1H),   7.64   (d,   J  =   7.0   Hz,   1H),   7.67   (d,   J  =  7.9  Hz,   1H),   9.13   (br-­‐‑s,   1H,   N1H);   13C   NMR   (125   MHz,   CDCl3)   δ:   25.1,  28.0,   28.4,   52.3,   54.4,   79.8,   83.9,   109.6,   119.2,   122.4,   122.9,   126.7,   129.6,  141.4,  155.3,  172.8.  FTIR (neat) cm–1: 3384 (br-s), 2979 (m), 1740 (s), 1701(s), 1592 (m), 1503 (s), 1438 (m), 1371 (m), 1334 (m), 1165 (m), 1130 (s),Org. Synth. 2015, 92, 373-385

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9.

1052 (m), 970 (s), 920 (s), 849 (m), 760 (s), 684(s); HRMS (ESI, TOF) (m/z)
calc’d for C23H33BN2O6 [M+H]+: 445.2510, found: 445.2508; mp 179–
181 ºC; Anal. calc’d for C23H33BN2O6: C, 62.17; H, 7.49; N, 6.30, found: C,
61.80; H, 7.23; N, 6.12. TLC (5% acetone, 15% dichloromethane,
80% hexanes), Rf = 0.17 (CAM, UV).
Mosher ester analysis provided an enantiomeric excess of >98% for thealcohol obtained from reduction of a sample of ester 1 that had been
made by protodeboronation of 7-borotryptophan 3 (see Note 5). This is
in full agreement with the expectation that this procedure does noterode the enantiopurity of 7-borotryptophan 3 with respect totryptophan 1.

Handling	
  and	  Disposal	
  of	
  Hazardous	
  Chemicals	  The procedures in this article are intended for use only by persons withprior training in experimental organic chemistry. All hazardous materials
should be handled using the standard procedures for work with chemicals
described in references such as "Prudent Practices in the Laboratory" (TheNational Academies Press, Washington, D.C., 2011 www.nap.edu). All
chemical waste should be disposed of in accordance with local regulations.
For general guidelines for the management of chemical waste, see Chapter 8of Prudent Practices.
In some articles in Organic Syntheses, chemical-specific hazards arehighlighted in red “Caution Notes” within a procedure. It is important torecognize that the absence of a caution note does not imply that no
significant hazards are associated with the chemicals involved in thatprocedure. Prior to performing a reaction, a thorough risk assessment
should be carried out that includes a review of the potential hazards
associated with each chemical and experimental operation on the scale thatis planned for the procedure. Guidelines for carrying out a risk assessmentand for analyzing the hazards associated with chemicals can be found in
Chapter 4 of Prudent Practices.
These procedures must be conducted at one's own risk. Organic
Syntheses, Inc., its Editors, and its Board of Directors do not warrant or
guarantee the safety of individuals using these procedures and hereby
disclaim any liability for any injuries or damages claimed to have resulted
from or related in any way to the procedures herein.

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Discussion	
  Indole derivatives are prevalent in many natural products andpharmaceutical compounds, mostly in the form of often-complex
tryptophan and tryptamine-derived motifs.4 The demand for such diversely
substituted indole structures has led to the development of a wide range of
methods for indole functionalization.5 With regards to tryptophan andtryptamine derivatives, selective functionalization at indole C7 has provenespecially difficult, with few methods available that are direct and readily
scalable.6 We sought to explore a direct C7 functionalization method for 3substituted indoles by utilizing arene C–H boronation as a means to thisend.7 Of particular relevance to us were reports into iridium-catalyzed
indole boronations,8 which Smith had initially shown in 2006 would
proceed selectively at C7 with C2-substituted indoles.8a These studies
inspired us to investigate a more streamlined process for direct C7boronation of tryptophan and tryptamine substrates in a single operation.
By taking advantage of the more nucleophilic/basic C2 position of C3substituted indoles, our two-step single-flask procedure provides expedientaccess to the corresponding C7-boronated compounds on multi-gram scale
through direct C7 activation of non-functionalized tryptamines andtryptophans.9 The premise behind this diboronation/protodeboronation
sequence was our recognition of the high propensity of five-memberedheterocycles to undergo rapid C2 protodemetalation.10
Examination of conditions for the diboronation of various N-protected
tryptamines demonstrated that exposure to excess pinacolborane (5 equiv),
catalytic amounts of [Ir(cod)OMe]2, and 4,4’-di-tert-butylbipyridine intetrahydrofuran at 60 °C, was sufficient to ensure full boronation at C2 andC7.9 Consistent with our C2 protodeboronation hypothesis, these 2,7diboronated indoles can be dissolved in dichloromethane followed byaddition of trifluoroacetic acid to cleanly afford the desired 7-boronatedindole derivatives.
As we were interested in converting these two steps into a single-flask
operation, we first explored simple acidification of the reaction medium
once the diboronation was complete. However, mere addition of an

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Table 1. Rapid synthesis of C7-boronated 3-substituted indole derivatives

Entry

R

[Ir(cod)OMe]2 (2.5 mol%)
4,4'-di-tert-butyl-2,2'-bipyridine(5.0 mol%), HBpin (5.0 equiv)
THF, 60 °C;

N
H

CH2Cl2, TFA, 0 → 23 °C

R

Bpin

YieldaProduct

Substrate

NMeSO2Mes

NMeSO2Mes

1b

60%
N
H

Bpin

N
H

NHCO2Me

2

3

N
H

N
H

NHCO2Me

Bpin

66%

N
H

Me

Me

N
H

N
H

Bpin

54%
58%c

CO2Me

CO2Me

NHCO2MeNHCO2Me

4
N
H

Bpin

N
H

OH

OH

5
N
H

84%
82%d
72%c

Bpin

N
H

63%

a Isolated yield after purification. b Boronation conducted at 80 °C.
c 2nd step: Pd(OAc)

2 (5 mol%), AcOH, 30 °C.

d Gram-scale reaction.

equivolume (with respect to tetrahydrofuran) of trifluoroacetic acid at 0 °C
led to global protodeboronation and recovery of starting material.
Gratifyingly, dilution of the reaction mixture with dichloromethaneOrg. Synth. 2015, 92, 373-385

379

DOI: 10.15227/orgsyn.092.0373

followed by the addition of trifluoroacetic acid at 0 °C, led to the desired
C2-protodeboronated tryptamine in 60% yield for the two-step process(entry 1, Table 1).9
We then focused our attention on expanding the substrate scope (Table
1) to other 3-substituted indoles. In all but one case (entry 1), a temperatureof 60 °C and reaction time of 4–7 h was found to be ideal for thediboronation reactions (entries 2–5, Table 1).9 These results highlighted thegeneral compatibility of our protocol with alcohol, carbamate, ester, andsulfonamide functional groups. The excellent yield obtained for a C7boronated tryptophan derivative (entry 4, Table 1) and its ready conversion
to the corresponding 7-halo, 7-hydroxy and 7-aryl tryptophan derivatives(Scheme 1) further highlight the versatility of this chemistry.9
CO 2MeNHCO 2Me

X

CO 2MeCuX2•2H 2O
MeOH, H 2O
80 °C
X=Cl, 93%
X=Br, 76%

N
H

CO 2MeNHCO 2MeOH

N
H

Cu2O, NH 3(aq)
NaI

NHCO 2MeBpin
H 2O2 (aq)
NaOH, THF
23 °C
65%

MeOH, 23 °C
85%

CO 2MeNHCO 2Me

I

N
H

N
H

CO 2MePd 2(dba) 3, S-Phos

NHCO 2MeBr
K 3PO 4
toluene, 80 °C
76%

N
H

OMe
OMe

Scheme 1. Representative derivatization of a C7-boronated tryptophan

The 2,7-diborotryptophan 4 (Scheme 2), resulting from C2/C7
diboronation of N-Boc tryptophan methyl ester (1) using our standard
iridium-catalyzed conditions,9 could be isolated chromatographically (ca.
88%, Note 4) from the crude reaction mixture after removal of volatiles.

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CO2Me
NHBoc

CO2Me

CO2Me
[Ir(cod)OMe]2
dtbpy, HBpin

NHBoc

NHBoc

Pd(OAc)2

BPin
N
H

THF, 60 °C, 12 h
1

~88%

BPin

N
H

AcOH, 30 °C
4

85%

BPin

N
H
3

Scheme 2. Two step sequence for C7 boronation of N-Boc tryptophan 1

We have developed milder conditions than those described in Table 1
for the C2 protodeboronation of the intermediate 2,7-diborotryptophan 4.
After exploring a range of additives in acetic acid, it was found that C2selective protodeboronation of 2,7-diborotryptophan 4 could be engenderedby inclusion of catalytic quantities of palladium(II) acetate. The optimal
temperature for this step was found to be 30 °C, delivering the desired NBoc 7-borotryptophan methyl ester 3 in 85% yield (Scheme 2). Further still,
the dried crude mixture from the diboronation step could also be subjectedto the same palladium-catalyzed protodeboronation conditions, once more
rendering this a two-step single-flask operation as described above.9

References	
  
	
  
1.

2.

3.
4.

Address: Massachusetts Institute of Technology, Department of Chemistry,
77 Massachusetts Avenue, 18-290, Cambridge, MA 02139. E-mail:movassag@mit.edu
We acknowledge financial support by NIH-NIGMS (GM089732 andGM074825) and the NSF under CCI Center for selective C–Hfunctionalization (CHE-1205646). R.P.L. thanks the Fonds de Recherche duQuébec – Nature et Technologies for a postdoctoral fellowship. K.A.
acknowledges support from the Institute of Transformative Bio-Molecules,
Nagoya University, and the NSF program for Science Across Virtual
Institutes for a summer fellowship.
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	  Org. Synth. 2015, 92, 373-385

383

DOI: 10.15227/orgsyn.092.0373

Appendix	  Chemical	
  Abstracts	
  Nomenclature	
  (Registry	
  Number)	
  N-Boc-L-Tryptophan methyl ester: L-Tryptophan, N-[(1,1dimethylethoxy)carbonyl]- (13139-14-5)(1,5-Cyclooctadiene)(methoxy)iridium(I) dimer: bis[(1,2,5,6- )-1,5cyclooctadiene]di-µ-methoxydi-; (12148-71-9)
4,4'-Di-tert-butyl-2,2'-bipyridine: 2,2'-Bipyridine, 4,4'-bis(1,1-dimethylethyl)-;(72914-19-3)
4,4,5,5-Tetramethyl-1,3,2-dioxaborolane: 1,3,2-Dioxaborolane, 4,4,5,5tetramethyl-; (25015-63-8 )Palladium(II) acetate: Acetic acid, palladium(2+) salt (2:1); (3375-31-3)

Kazuma Amaike is pursuing his graduate studies
in Professor Kenichiro Itami’s group at Nagoya
University, Nagoya, Japan. His studies focus on a
range projects related to C–H activation and thesynthesis of natural products. In 2013, he joined
the laboratory of Professor Mohammad
Movassaghi at MIT as a visiting graduate student
via the National Science Foundation CCI Centerfor selective C–H functionalization.

Richard Loach was born in Birmingham (U.K.)
and graduated from Imperial College, London in2003 with a B.Sc. in Chemistry. In 2007 he joined
the research group of Professor John Boukouvalasat Laval University in Québec (Canada), earning
his Ph.D. in 2013 for his studies on the total
syntheses of novel γ-hydroxybutenolide natural
products. In 2014, he was granted a FRQNT
fellowship to pursue his postdoctoral research in
Professor Mohammad Movassaghi’s group at
MIT. He is currently working on the total
synthesis of alkaloid natural products.

Org. Synth. 2015, 92, 373-385

384

DOI: 10.15227/orgsyn.092.0373

Mohammad Movassaghi carried out his
undergraduate research with Professor Paul A.
Bartlett at UC Berkeley, where he received his
B.S. degree with Honors in chemistry in 1995. Hecompleted his graduate studies in Professor
Andrew G. Myers’ group as a Roche predoctoral
fellow at Harvard University. In 2001, Mo joined
Professor Eric N. Jacobsen’s group at Harvard
University as a Damon Runyon Cancer Research
Foundation postdoctoral fellow. In 2003, hejoined the faculty at MIT and his research
program focuses on the total synthesis ofalkaloids in concert with the discovery anddevelopment of new reactions for organic
synthesis.

Danilo Pereira de Sant’Ana was born in Rio deJaneiro-RJ, Brazil. He received his B.S. and M.S.
degrees at the Federal University of Rio deJaneiro, Brazil (UFRJ) (2008) under thesupervision of Prof. Paulo Roberto Ribeiro Costa.
He got his Ph.D. in cotutelle between the State
University of Campinas-SP, Brazil (UNICAMP)
and National Graduate School of Chemistry,
Montpellier, France (ENSCM) (2014) under thesupervision of Prof Luiz Carlos Dias and JeanMarc Campagne. He is currently a Postdoctoral
Fellow with Prof. Richmond Sarpong at UC
Berkeley, working on the total synthesis ofprenylated indole alkaloid natural products.

	
  
	
  

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(S)-Methyl 3-(2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-indol-3-yl)-2-(tert-butoxycarbonylamino)propanoate

S4

(S)-Methyl 3-(2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-indol-3-yl)-2-(tert-butoxycarbonylamino)propanoate

S5

4.5

1.45
1.41
1.40
1.38
1.36

3.29

5.0

3.33
3.32

3.69

1.00

Title
Spectrometer
Solvent
Temperature
Pulse Sequence
Experiment
Probe

5.08
5.07
4.67
4.66
4.66
4.65
4.65
4.63

1
2
3
4
5
6
7

1.00

Parameter

7.70
7.68
7.67
7.66
7.17
7.15
7.14
7.08
7.07

9.15

methyl (S)-2-((tert-butoxycarbonyl)amino)-3-(7-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-indol-3-yl)propanoate

Value
OS1R2Biii.1.fid
AV-500
OS1R2Biii.1.fid
CDCl3
CC: 12182012 AV-500 TBIP probe
294.6
1H 1D NMR
zg30
1D
5 mm TBI 1H/ 31P/ D-BB Z-GRD Z8641/ 0004

8 Number of Scans
8
9 Receiver Gain
128.0
10 Relaxation Delay
0.1000
11 Pulse Width
7.600012 Presaturation Frequency
13 Acquisition Time
14 Acquisition Date
15 Modification Date
16 Class

3.17192015-09-03T10:54:49
2015-09-03T10:54:56

12.5

12.0

11.5

11.0

10.5

10.0

9.5

9.0

8.5

8.0

7.5

7.0

6.5

6.0
5.5
f1 (ppm)

4.0

23.36

2.08

1.14
1.12

2.19

1.15

17 Spectrometer Frequency 500.23
18 Spectral Width10330.6
19 Lowest Frequency-2092.9
20 Nucleus
1H
21 Acquired Size
32768
22 Spectral Size
65536

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0.0

Parameter

220

28.44
28.00
25.10

54.35
52.33

83.93

109.64

Value

1
2
3
4
5
6
7

Title
Spectrometer
Solvent
Temperature
Pulse Sequence
Experiment
Probe

8
9
10
11
12

Number of Scans
Receiver Gain
Relaxation Delay
Pulse Width
Presaturation Frequency

469
912.3
2.00009.0000

13
14
15
16

Acquisition Time
Acquisition Date
Modification DateClass

0.79302015-09-03T14:56:06
2015-09-03T14:59:12

17
18
19
20
21
22

Spectrometer Frequency
Spectral Width
Lowest Frequency
NucleusAcquired Size
Spectral Size

125.6941322.3-8072.8
13C
32768
65536

210

200

190

129.56126.72122.87122.42
119.20141.35155.32172.80methyl (S)-2-((tert-butoxycarbonyl)amino)-3-(7-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-indol-3-yl)propanoate

OS1R2BiiiC.13.fid
DRX-500
CDCl3
293.4
OS1R2BiiiC.13.fid
zgpg30ZBO probe 13C starting parameters. Rev 6/12/12 CGC
DRX-500 5mm
With CPD1D
proton decoupling. Use ns*td0 scans
5 mm BBO BB-1H Z-GRD Z8007/ 85
TBIC 103013

180

170

160

150

140

130

120

110

100
90
f1 (ppm)

80

70

60

50

40

30

20

10

0

-10