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Boc-Amino Acidsa | Solventb | Base | Time (hr)c | Yield, (%) | mp, (°C) | [α]20D | Remarks |
---|---|---|---|---|---|---|---|
Boc-Ala-OH | A | NaOH | 16 | 92–94 | 82–83 | −25.5 (acetic acid, c 2.0) | pH 8.0e |
Boc-β-Ala-OH | A | NaOH | 16 | 85–86 | 76–77 | ||
Boc-Arg-OH | B | — | 15 | 88 | 159–160 (dec) | −6.8 (acetic acid, c 1.0) | Extraction with n-butyl alcohol |
Boc-Arg(NO2)-OHd | B | NaOH | 15 | 82 | 107 | −22.0 (pyridine, c 2.0) | pH 8.5e |
Boc-Asn-OH | C | NaOH | 18 | 80–81 | 176 (dec) | −7.2 (dimethylformamide, c 2.0) | 5 hr, 45–50°C |
Boc-Asp(OBzl)-OH | A | NaOH | 16 | 81–89 | 101–102 | −19.7 (dimethylformamide, c 2.0) | pH 8.0e |
Boc-Cys(Bzl)-OH | B | NaOH | 15 | 65 | 86–87 | −43.4 (acetic acid, c 1.0) | |
(Boc-Cys-OH)2 | D | NaOH | 16 | 85 | 143–145 (dec) | −115.6 (acetic acid, c 2.0) | |
Boc-Gln-OH | E | NaOH | 18 | 76 | 125 (dec) | −3.4 (ethanol, c 2.0) | pH 8.0e |
Boc-Glu(OBzl)-OHf | B | NaOH | 15 | 86 | 142–143 | +13.2(methanol, c 1.0) | pH 8.5–9e |
Boc-Gly-OH | A | NaOH | 16 | 96 | 87–88 | ||
Boc-His(Boc)-OH | A | KHCO3 | 18 | 75 | 170 (dec) | +19.5 (chloroform, c 2.0) | |
Boc-Ile-OH | A | NaOH | 16 | 78 | 69–71 | +2.8 (acetic acid, c 2.0) | |
Boc-Leu-OHg | A | NaOH | 18 | 96 | 85–87 | −24.7 (acetic acid, c 2.0) | |
Boc-Lys(Boc)-OHf | A | NaOH | 16 | 82 | 138–139 | +6.1 (dimethylformamide, c 1.5) | |
Boc-Lys(CBZ)-OH | A | NaOH | 18 | 96 | Oil | ||
Boc-Met-OH | A | NaOH | 18 | 60h | 50–51 | −22.8 (methanol, c 1.3) | |
Boc-Met-OHf | A | NaOH | 18 | 85 | 139–140 | +18.2 (ethanol, c 2.0) | |
Boc-Pro-OH | A | NaOH | 12 | 95 | 134–135 | −60.6 (acetic acid, c 2.0) | |
Boc-Ser-OH | A | NaOH | 16 | 66–82 | 86–88 | −3.6 (acetic acid, c 2.0) | pH 8.5–9e |
Boc-Ser(Bzl)-OH | B | NaOH | 16 | 90 | 62–63 | +19.2 (80% ethanol, c 2.0) | pH 8.5–9e |
Boc-Thr-OH | A | NaOH | 16 | 85 | 71–73 | −8.2 (acetic acid, c 1.0) | |
Boc-Trp-OHi | A | NaOH | 16 | 96 | 137–138 (dec) | −18.2 (dimethylformamide, c 1.0) | |
Boc-Trp-(FOR)-OHf | F | Et3N | 48 | 61 | 158–159k | +36.0 (ethanol, c 2.0) | |
Boc-Tyr-OH | A | NaOHl | 24 | 75 | 137m | +2.6 (acetic acid, c 1.0) | |
Boc-Tyr-OHf | A | NaOHl | 24 | 84 | 216 | +2.6 (acetic acid, c 1.0) | |
Boc-Tyr(Bzl)-OH | B | NaOH | 18 | 70 | 110–111 | +27.6 (ethanol, c 1.0) | pH 10.4e |
Boc-Tyr(2,6-Cl2-Bzl)-OH | A | NaOH | 24 | 48 | 104 (dec) | +20.6 (ethanol, c 2.0) | |
Boc-Val-OH | A | NaOH | 16 | 85 | 76–78 | −7.5 (acetic acid, c 1.0) | |
bSolvent systems: A: tert-butyl alcohol–water; B: dioxane–water; C: dimethylformamide–water; D: methanol–water; E: acetonitrile–water; F: dimethylformamide. |
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cThe reaction was generally carried out at room temperature after the exothermic starting period had subsided. Progress of the reaction was monitored by TLC. Reaction times are not optimized. |
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dCrystallizes with 15% solvent (ethyl acetate). |
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epH control is necessary. |
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fDicyclohexylamine salt. |
Appendix
Compounds Referenced (Chemical Abstracts Registry Number)
Ethyl or isopropyl acetate
Boc-Ala-OH
Boc-β-Ala-OH
Boc-Arg-OH
Boc-Arg(NO2)-OH
Boc-Asn-OH
Boc-Asp(OBzl)-OH
Boc-Cys(Bzl)-OH
(Boc-Cys-OH)2
Boc-Gln-OH
Boc-Glu(OBzl)-OH
Boc-Gly-OH
Boc-His(Boc)-OH
Boc-Ile-OH
Boc-Leu-OH
Boc-Lys(Boc)-OH
Boc-Lys(CBZ)-OH
Boc-Met-OH
Boc-Pro-OH
Boc-Ser-OH
Boc-Ser(Bzl)-OH
Boc-Thr-OH
Boc-Trp-OH
Boc-Trp-(FOR)-OH
Boc-Tyr-OH
Boc-Tyr(Bzl)-OH
Boc-Tyr(2,6-Cl2-Bzl)-OH
Boc-Val-OH
ethanol (64-17-5)
acetic acid (64-19-7)
ethyl acetate (141-78-6)
methanol (67-56-1)
ethyl ether (60-29-7)
acetonitrile (75-05-8)
sodium hydroxide (1310-73-2)
chloroform (67-66-3)
sodium bicarbonate (144-55-8)
sodium sulfate (7757-82-6)
carbon dioxide (124-38-9)
potassium hydrogen sulfate (7646-93-7)
n-butyl alcohol (71-36-3)
pyridine (110-86-1)
Glycine (513-29-1)
Pentane (109-66-0)
β-Alanine (107-95-9)
magnesium sulfate (7487-88-9)
dioxane (5703-46-8)
L-phenylalanine (63-91-2)
dimethylformamide (68-12-2)
hexane (110-54-3)
tert-butyl alcohol (75-65-0)
tert-Butyl azidoformate (1070-19-5)
N-tert-butoxycarbonyloxyimino-2-phenylacetonitrile (58632-95-4)
tert-Butyl phenyl carbonate (6627-89-0)
Di-tert-butyl dicarbonate (24424-99-5)
tert-butyl 2,4,5-trichlorophenyl carbonate (16965-08-5)
tert-butyl α-methoxyvinyl carbonate
N-tert-Butoxycarbonyl-L-phenylalanine, L-Phenylalanine, N-[(1,1-dimethylethoxy)carbonyl]- (13734-34-4)
tert-butyl 4-nitrophenyl carbonate (13303-10-1)
tert-butyl pentachlorophenyl carbonate (18942-25-1)
tert-butyl 8-quinolyl carbonate
N-tert-butoxycarbonyl-1H-1,2,4-triazole (41864-24-8)