Please cite this article in press as: Amatuni et al., Concise Chemoenzymatic Total Synthesis and Identification of Cellular Targets of Cepafungin I, Cell
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Brief Communication
(
S,E)-4-((S)-2,6-diaminohexanamido)pent-2-enoic acid–2,2,2-trifluoroacetic acid (1/2) (S20). Dipeptide S19 (431 mg, 0.863 mmol, 1
eq) was dissolved in 22 mL of a freshly prepared solution of ‘‘Reagent B’’ (88:5:5:2 trifluoroacetic acid:phenol:water:triisopropylsi-
lane). After stirring for 1 hour at room temperature, the reaction was diluted with 30 mL toluene and concentrated in vacuo to dryness,
followed by an additional evaporation from 30 mL toluene. The residue was then dissolved in 2 mL methanol and added dropwise to
ꢀ
ꢀ
1
into 50 mL diethyl ether at 0 C from 1.5 mL methanol. The solids were collected by centrifugation as above, then dried from methanol
00 mL diethyl ether at 0 C. The solids were collected by centrifugation at 4200 RPM for 10 minutes at 4 C, then precipitated again
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to provide S20 as an off-white solid (356 mg, 0.755 mmol, 88%).
1
3
H NMR (600 MHz, CD OD): d 6.83 (dd, J = 15.7, 5.4 Hz, 1H), 5.86 (dd, J = 15.7, 1.6 Hz, 1H), 4.69 – 4.59 (m, 1H), 3.87 (t, J = 6.4 Hz,
1
H), 2.98 – 2.89 (m, 2H), 1.99 – 1.82 (m, 2H), 1.76 – 1.66 (m, 2H), 1.54 – 1.42 (m, 2H), 1.33 (d, J = 7.0 Hz, 3H).
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1
3
C NMR (151 MHz, CD OD): d 170.1, 169.3, 149.0, 122.7, 54.2, 47.4, 40.3, 32.1, 28.2, 22.9, 19.7.
2
D
3
½
aꢂ = –13.6 (c 0.530, MeOH)
–
–
20 3 3
HRMS (ESI-TOF): calculated for free base C11H N O ([M–H] ) 242.2521, found 242.1511.
(
5S,8S,E)-8-amino-5-methyl-1,6-diazacyclododec-3-ene-2,7-dione (S21). Macrocycle precursor S20 (200 mg, 0.424 mmol, 1 eq)
was dissolved in 424 mL anhydrous DMF. The solution was treated with diisopropylethylamine (296 mL, 1.70 mmol, 4 eq), followed
by solid 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methyl-morpholinium tetrafluoroborate (DMTMMT) (209 mg, 0.637 mmol, 1.5 eq) at
room temperature. The reaction was stirred under argon for 27 hours, then quenched with 10 mL water and concentrated in vacuo
to dryness. The residue was dissolved in 2 mL methanol and precipitated into 50 mL diethyl ether with rapid stirring. The solids were
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collected by centrifugation at 4200 RPM for 15 minutes at 4 C to yield crude S21 as a tan solid (276 mg, 0.187 mmol, 44% from S20,
1
3
0
9% from S19). Yield was determined by H NMR analysis of a 6.2 mg crude sample with 4-toluenesulfonamide (7.7 mg,
.0450 mmol) added as internal standard.
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3
H NMR (400 MHz, CD OD): 4-toluenesulfonamide: d 7.82 – 7.72 (m, 2H), 7.40 – 7.30 (m, 2H), 2.42 (s, 3H). Compound S21: 7.03
(
dd, J = 15.4, 4.9 Hz, 1H), 6.35 (dd, J = 15.5, 1.4 Hz, 1H), 4.66 – 4.58 (m, 1H), 4.16 (t, J = 3.7 Hz, 1H), 3.58 – 3.44 (m, 2H), 2.36 – 2.24 (m,
H), 1.98 – 1.77 (m, 2H), 1.77 – 1.62 (m, 2H).
HRMS (ESI-TOF): calculated for C11
1
–
–
18 3 2
H N O ([M–H] ) 224.1404, found 224.1406.
(
2E,4E)-N-((2S,3R)-3-hydroxy-1-(((5S,8S,E)-5-methyl-2,7-dioxo-1,6-diazacyclododec-3-en-8-yl)amino)-1-oxobutan-2-yl)-11-meth-
yldodeca-2,4-dienamide (21). Acid 14 (42 mg, 0.134 mmol, 2 eq) and crude desoxyglidobamine S21 (100 mg, ꢁ0.0670 mmol as
1
judged by H NMR analysis, 1 eq) were dissolved in 3.4 mL anhydrous DMF and cooled to 0 C. To the mixture was added diisopro-
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pylethylamine (35 mL, 0.201 mmol, 3 eq), followed by solid DEPBT (40 mg, 0.134 mmol, 2 eq). The reaction was warmed to room tem-
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perature and stirred overnight, and the reaction progress was monitored by LCMS. At 24 hours, the reaction was cooled to 0 C and
quenched with 2 mL saturated NH
bined organic layers were washed with brine, dried over Na
.2 mm PTFE membrane filter in methanol, then purified by reversed-phase HPLC (gradient 30–60% acetonitrile in water over 35 mi-
nutes, 0.1% formic acid added) to provide desoxycepafungin I (21) as a fluffy white powder after lyophilization (7.9 mg, 0.0152 mmol,
4
Cl. The mixture was extracted with ethyl acetate (4 x 4 mL), then n-butanol (3 x 4 mL). The com-
2
SO , and concentrated in vacuo. The residue was filtered through a
4
0
2
3%, 9% from S24).
1
3 2
H NMR (600 MHz, (CD ) SO): d 8.44 (d, J = 7.9 Hz, 1H), 7.99 (d, J = 8.5 Hz, 1H), 7.62 (d, J = 7.2 Hz, 1H), 7.35 (dd, J = 8.0, 6.1 Hz,
1H), 7.00 (dd, J = 15.1, 10.8 Hz, 1H), 6.78 (dd, J = 15.3, 4.7 Hz, 1H), 6.23 (dd, J = 15.4, 1.4 Hz, 1H), 6.21 – 6.15 (m, 2H), 6.09 (dt, J = 14.8,
6.9 Hz, 1H), 4.54 – 4.48 (m, 1H), 4.44 – 4.36 (m, 1H), 4.32 (dd, J = 8.5, 3.9 Hz, 1H), 4.02 – 3.96 (m, 1H), 3.80 (s, 1H), 3.32 – 3.23 (m, 1H),
2.98 – 2.91 (m, 1H), 2.13 (q, J = 7.2 Hz, 2H), 2.10 – 2.03 (m, 1H), 1.74 – 1.64 (m, 1H), 1.50 (hept, J = 6.7 Hz, 1H), 1.46 – 1.41 (m, 1H), 1.41
– 1.35 (m, 2H), 1.35 – 1.29 (m, 1H), 1.29 – 1.22 (m, 5H), 1.20 (d, J = 7.0 Hz, 3H), 1.17 – 1.11 (m, 2H), 1.02 (d, J = 6.3 Hz, 3H), 0.98 – 0.90
(
m, 1H), 0.85 (d, J = 6.6 Hz, 6H).
1
3
3 2
C NMR (151 MHz, (CD ) SO): d 170.5, 169.4, 165.8, 165.5, 146.7, 142.1, 139.8, 128.6, 122.9, 118.4, 66.6, 58.1, 51.5, 45.6, 38.4,
7.9, 32.2, 30.2, 29.6, 28.8, 28.4, 27.4, 26.6, 22.5, 19.6, 18.3, 17.1.
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e13 Cell Chemical Biology 27, 1–9.e1–e18, October 15, 2020