132388-59-1

Basic information

• Product Name: Fmoc-N-trityl-L-asparagine
• Synonyms: N-ALPHA-FMOC-N-GAMMA-TRITYL-L-ASPARAGINE;FMOC-ASPARAGINE(TRT);FMOC-ASN(XAN)-OH;FMOC-ASN(TRT)-OH;FMOC-ASN(TRT);FMOC-L-ASN(TRITYL);FMOC-L-ASN(TRT)-OH;FMOC-L-ASPARGINE(TRITYL)
• CAS NO: 132388-59-1
• Molecular Formula: C₃₈H₃₂N₂O₅
• Molecular Weight: 596.67
• Product Categories: Protected Amino Acids;Fluorenes, Flurenones;Amino Acids;Asparagine [Asn, N];Fmoc-Amino Acids and Derivatives;Amino Acids (N-Protected);Biochemistry;Fmoc-Amino Acids;Fmoc-Amino acid series
• Mol File: 132388-59-1.mol

Chemical Properties

• Melting Point: 201-204 °C(lit.)
• Boiling Point: 858.1 °C at 760 mmHg
• Flash Point: 472.8 °C
• Appearance: White to off white free flowing powder
• Density: 1.271 g/cm³
• Vapor Pressure: 2.26E-31mmHg at 25°C
• Refractive Index: -19 ° (C=1, DMF)
• Storage Temp.: 2-8°C
• Solubility: <0.00005g/l
• PKA: 3.79±0.10(Predicted)
• BRN: 4343823
• CAS DataBase Reference: Fmoc-N-trityl-L-asparagine(CAS DataBase Reference)
• NIST Chemistry Reference: Fmoc-N-trityl-L-asparagine(132388-59-1)
• EPA Substance Registry System: Fmoc-N-trityl-L-asparagine(132388-59-1)

Safety Data

• Statements: 53
• Safety Statements: 24/25-61
• RIDADR: UN 3077 9 / PGIII
• WGK Germany: 2
• F: 3-10
• HazardClass: IRRITANT
• Hazardous Substances Data: 132388-59-1(Hazardous Substances Data)

Usage

Uses

Used in Chemical Synthesis:
Fmoc-N-trityl-L-asparagine is used as a building block in chemical synthesis for the creation of complex organic molecules. Its trityl group provides steric hindrance and protection, which is crucial for the selective synthesis of target compounds.
Used in Peptide Chemistry:
In peptide chemistry, Fmoc-N-trityl-L-asparagine is used as a protected amino acid for the stepwise assembly of peptide chains. The Fmoc (9-fluorenylmethoxycarbonyl) group serves as a protecting group for the amino group, allowing for the controlled addition of amino acids during solid-phase peptide synthesis. This protection is essential to prevent unwanted side reactions and ensure the correct sequence of the peptide.
Used in Pharmaceutical Industry:
Fmoc-N-trityl-L-asparagine is used as a key intermediate in the synthesis of pharmaceutical compounds, particularly in the development of peptide-based drugs. Its role in facilitating the synthesis of complex peptide structures makes it a valuable asset in the discovery and production of new therapeutic agents.
Used in Research and Development:
In research and development settings, Fmoc-N-trityl-L-asparagine is used as a reagent for studying the properties and interactions of amino acids and peptides. Its controlled synthesis and modification capabilities make it an ideal candidate for exploring the structure-function relationships in biologically active peptides.

InChI:InChI=1/C38H32N2O5/c41-35(40-38(26-14-4-1-5-15-26,27-16-6-2-7-17-27)28-18-8-3-9-19-28)24-34(36(42)43)39-37(44)45-25-33-31-22-12-10-20-29(31)30-21-11-13-23-32(30)33/h1-23,33-34H,24-25H2,(H,39,44)(H,40,41)(H,42,43)/p-1/t34-/m0/s1

Synthetic route

N-(9H-fluoren-2-ylmethoxycarbonyloxy)succinimide (82911-69-1) + (S)-2-Amino-N-trityl-succinamic acid (132388-58-0) → L-Asn(Trt) (132388-59-1)

Fmoc-Asn(TrT)-F → L-Asn(Trt) (132388-59-1)

Conditions	Yield
With water In N,N-dimethyl-formamide for 24h; Product distribution; Ambient temperature; effect of water content on stability of various Fmoc-amino acid fluorides;

triphenylmethyl alcohol (76-84-6) → L-Asn(Trt) (132388-59-1)

Conditions	Yield
Multi-step reaction with 2 steps 1: 75 percent / acetic anhydride, conc.H2SO4 / acetic acid / 1.25 h / 60 °C View Scheme
Multi-step reaction with 3 steps 1: acetic anhydride, conc.H2SO4 / acetic acid / 1 h / 50 °C 2: H2 / Pd-C View Scheme

N-benzyloxycarbonyl-N'-trityl-L-asparagine (132388-57-9) → L-Asn(Trt) (132388-59-1)

Conditions	Yield
Multi-step reaction with 2 steps 1: H2 / Pd-C View Scheme

triphenylmethyl alcohol (76-84-6) + Fmoc-Asn-OH (71989-16-7) + 1,2-dichloro-ethane (107-06-2) → L-Asn(Trt) (132388-59-1)

Conditions	Yield
With sulfuric acid; acetic anhydride In tetrahydrofuran; methanol; di-isopropyl ether; water; acetic acid; ethyl acetate

aqueous potassium bisulfate + H-Asn(Trt)-OH.0.5 H2 O + N-(9H-fluoren-2-ylmethoxycarbonyloxy)succinimide (82911-69-1) → L-Asn(Trt) (132388-59-1)

Conditions	Yield
With triethylamine In tetrahydrofuran; di-isopropyl ether; water; ethyl acetate

Fmoc-Asn(Trt)-OBt → L-Asn(Trt) (132388-59-1) + benzotriazol-1-ol (2592-95-2)

Conditions	Yield
With water for 6h; Kinetics;

C119H188N12O14S (1258442-46-4) + L-Asn(Trt) (132388-59-1) → C157H218N14O18S (1258442-38-4)

Conditions	Yield
With benzotriazol-1-ol; O-(1H-benzotriazol-1-yl)-N,N,N',N'-tetramethyluronium hexafluorophosphate; N-ethyl-N,N-diisopropylamine In tetrahydrofuran at 20℃;	100%

(4-(hydroxymethyl)phenyl)diphenylphosphine oxide (5068-20-2) + L-Asn(Trt) (132388-59-1) → C57H47N2O6P

Conditions	Yield
Stage #1: (4-(hydroxymethyl)phenyl)diphenylphosphine oxide; L-Asn(Trt) With 1-ethyl-(3-(3-dimethylamino)propyl)-carbodiimide hydrochloride In dichloromethane at 0℃; for 0.166667h; Stage #2: With dmap In dichloromethane at 20℃; for 2h;	99%

L-Asn(Trt) (132388-59-1) + methyl iodide (74-88-4) → methyl (S)-2-((9H-fluoren-9-yl)methoxycarbonylamino)-4-oxo-4-(tritylamino)butanoate

Conditions	Yield
With potassium carbonate In N,N-dimethyl-formamide at 0 - 20℃; for 1h;	99%

L-Asn(Trt) (132388-59-1) + D-Asn(Trt)-OBn → Fmoc-L-Asn(Trt)-D-Asn(Trt)-OBn

Conditions	Yield
With 1-hydroxy-7-aza-benzotriazole; 1-ethyl-(3-(3-dimethylamino)propyl)-carbodiimide hydrochloride In N,N-dimethyl-formamide at 0 - 25℃;	98%
With 1-hydroxy-7-aza-benzotriazole; 1-ethyl-(3-(3-dimethylamino)propyl)-carbodiimide hydrochloride	98%

Fmoc-Pro-OH (71989-31-6) + Fmoc-(tBu)Asp-OH (71989-14-5) + Fmoc-Lys(tert-butoxycarbonyl) (71989-26-9) + L-Asn(Trt) (132388-59-1) + Fmoc-(S)-2-aminohexanoic acid (77284-32-3) + N-(9-fluorenylmethoxycarbonyl)-D-valine (84624-17-9) → C58H82N8O12

Conditions

Yield

Stage #1: Fmoc-(tBu)Asp-OH With O-(1H-6-chlorobenzotriazole-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate; N-ethyl-N,N-diisopropylamine In N,N-dimethyl-formamide for 0.833333h; 2-chlorotrityl resin; Automated synthesizer; Stage #2: With piperidine In N,N-dimethyl-formamide for 0.0833333h; 2-chlorotrityl resin; Automated synthesizer; Stage #3: Fmoc-Pro-OH; Fmoc-Lys(tert-butoxycarbonyl); L-Asn(Trt); Fmoc-(S)-2-aminohexanoic acid; N-(9-fluorenylmethoxycarbonyl)-D-valine Further stages;

97%

L-Asn(Trt) (132388-59-1) + tert-butyl 4-aminobutanoate hydrochloride → Fmoc-Asn(Trt)-GABA-OtBu

Conditions	Yield
With 4-methyl-morpholine; benzotriazol-1-ol; O-(1H-benzotriazol-1-yl)-N,N,N',N'-tetramethyluronium hexafluorophosphate In dichloromethane Inert atmosphere;	97%

L-Asn(Trt) (132388-59-1) + tert-butylamine (75-64-9) → Fmoc-Asn(Trt)-NHtBu (1370293-55-2)

Conditions	Yield
With 4-methyl-morpholine; isobutyl chloroformate In tetrahydrofuran at -20 - -18℃; for 2h;	96%

L-Asn(Trt) (132388-59-1) + 4-methoxycarbonyl aniline (619-45-4) → methyl (S)-4-(2-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)-4-oxo-4-(tritylamino)butanamido)benzoate

Conditions	Yield
With triethylamine; trichlorophosphate In dichloromethane at 0℃; for 2h;	96%
With triethylamine; trichlorophosphate In dichloromethane at 0℃; for 2h; Inert atmosphere;	13.97 g

HCl*H-Ser(tBu)-Phe-Arg(Pbf)-Tyr(tBu)-OKb, Kb=2,4-didocosyloxybenzyl + L-Asn(Trt) (132388-59-1) → HCl*H-Asn(Trt)-Ser(tBu)-Phe-Arg(Pbf)-Tyr(tBu)-Okb, Kb=2,4-didocosyloxybenzyl

Conditions

Yield

Stage #1: HCl*H-Ser(tBu)-Phe-Arg(Pbf)-Tyr(tBu)-OKb, Kb=2,4-didocosyloxybenzyl; L-Asn(Trt) With 1-[(1-(cyano-2-ethoxy-2-oxoethylidenaminooxy)dimethylamino-morpholino)]-uronium hexafluorophosphate; N-ethyl-N,N-diisopropylamine; ethyl cyanoglyoxylate-2-oxime In tetrahydrofuran; N,N-dimethyl-formamide at 20℃; for 0.166667h; Stage #2: With piperidine; 1,8-diazabicyclo[5.4.0]undec-7-ene In tetrahydrofuran; N,N-dimethyl-formamide at 20℃; for 0.166667h; Stage #3: With hydrogenchloride In tetrahydrofuran; water; N,N-dimethyl-formamide pH=Ca. 6;

95.4%

L-Asn(Trt) (132388-59-1) + tert-butyldimethylsilyl chloride (18162-48-6) → (S)-Nα-(Fluoren-9-ylmethoxycarbonyl)-Nγ-tritylasparagine tert-butyldimethylsilyl ester (313944-83-1)

Conditions	Yield
With dmap; N-ethyl-N,N-diisopropylamine In dichloromethane at 0 - 20℃; for 1.41667h; Esterification;	95%

N-[(9H-fluoren-9-ylmethoxy)carbonyl]-L-alanine (35661-39-3) + C20H18NO4Pol + L-Asn(Trt) (132388-59-1) + 2-(9H-fluoren-9-ylmethoxycarbonylamino)-pent-4-enoic acid (146549-21-5) + N-(tert-butoxycarbonyl)-D-allylglycine (170899-08-8) + (R)-2-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)pent-4-enoic acid (170642-28-1) → 2-[2-(2-{2-[2-(2-tert-butoxycarbonylamino-pent-4-enoylamino)-propionylamino]-pent-4-enoylamino}-pent-4-enoylamino)-3-(trityl-carbamoyl)-propionylamino]-pent-4-enoic acid methyl ester (936116-88-0)

Conditions

Yield

Stage #1: C20H18NO4Pol With piperidine In 1-methyl-pyrrolidin-2-one not specified; Stage #2: L-Asn(Trt) With (benzotriazo-1-yloxy)tris(dimethylamino)phosphonium hexafluorophosphate; N-ethyl-N,N-diisopropylamine In 1-methyl-pyrrolidin-2-one not specified; Stage #3: N-[(9H-fluoren-9-ylmethoxy)carbonyl]-L-alanine; 2-(9H-fluoren-9-ylmethoxycarbonylamino)-pent-4-enoic acid; N-(tert-butoxycarbonyl)-D-allylglycine; (R)-2-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)pent-4-enoic acid Further stages;

95%

L-Asn(Trt) (132388-59-1) → (S)-2-Amino-N-trityl-succinamic acid (132388-58-0)

Conditions	Yield
With sodium azide In N,N-dimethyl-formamide at 50℃; for 12h;	95%

4-aminobenzenemethanol (623-04-1) + L-Asn(Trt) (132388-59-1) → 9H-fluorene-9-ylmethyl[(2S)-1-{[4-(hydroxymethyl)phenyl]amino}-1,4-dioxo-4-(tritylamino)butane-2-yl]carbamate

Conditions	Yield
With N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline In tetrahydrofuran at 20℃;	93%
Stage #1: L-Asn(Trt) With N-[(dimethylamino)-3-oxo-1H-1,2,3-triazolo[4,5-b]pyridin-1-yl-methylene]-N-methylmethanaminium hexafluorophosphate In N,N-dimethyl-formamide for 0.5h; Stage #2: 4-aminobenzenemethanol With N-ethyl-N,N-diisopropylamine In N,N-dimethyl-formamide at 0 - 20℃; for 3h;	90%
With N-ethyl-N,N-diisopropylamine; N-[(dimethylamino)-3-oxo-1H-1,2,3-triazolo[4,5-b]pyridin-1-yl-methylene]-N-methylmethanaminium hexafluorophosphate In dichloromethane; N,N-dimethyl-formamide
With N-ethyl-N,N-diisopropylamine; N-[(dimethylamino)-3-oxo-1H-1,2,3-triazolo[4,5-b]pyridin-1-yl-methylene]-N-methylmethanaminium hexafluorophosphate In N,N-dimethyl-formamide at 0 - 20℃; for 3.5h;
With N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline In tetrahydrofuran at 20℃;	19.2 g

N-(fluoren-9-ylmethoxycarbonyl)glycine (29022-11-5) + Fmoc-Pro-OH (71989-31-6) + Fmoc-(tBu)Asp-OH (71989-14-5) + Fmoc-Ile-OH (71989-23-6) + Fmoc-Lys(tert-butoxycarbonyl) (71989-26-9) + L-Asn(Trt) (132388-59-1) → C55H76N8O12

Conditions

Yield

Stage #1: Fmoc-(tBu)Asp-OH With O-(1H-6-chlorobenzotriazole-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate; N-ethyl-N,N-diisopropylamine In N,N-dimethyl-formamide for 0.833333h; 2-chlorotrityl resin; Automated synthesizer; Stage #2: With piperidine In N,N-dimethyl-formamide for 0.0833333h; 2-chlorotrityl resin; Automated synthesizer; Stage #3: N-(fluoren-9-ylmethoxycarbonyl)glycine; Fmoc-Pro-OH; Fmoc-Ile-OH; Fmoc-Lys(tert-butoxycarbonyl); L-Asn(Trt) Further stages;

93%

N-(fluoren-9-ylmethoxycarbonyl)glycine (29022-11-5) + C42H38N4O9 + Fmoc-(tBu)Asp-OH (71989-14-5) + L-Asn(Trt) (132388-59-1) + Nα-(9-fluorenylmethyloxycarbonyl)-Nγ-2,2,4,6,7-pentamethyldihydrobenzofuran-5-sulfonyl-L-arginine → C51H69N17O16

Conditions	Yield
Stage #1: Fmoc-(tBu)Asp-OH With N-ethyl-N,N-diisopropylamine In dichloromethane for 4h; Inert atmosphere; Stage #2: With piperidine In N,N-dimethyl-formamide for 0.35h; Stage #3: N-(fluoren-9-ylmethoxycarbonyl)glycine; C42H38N4O9; L-Asn(Trt); Nα-(9-fluorenylmethyloxycarbonyl)-Nγ-2,2,4,6,7-pentamethyldihydrobenzofuran-5-sulfonyl-L-arginine Further stages;	92%

N-(fluoren-9-ylmethoxycarbonyl)glycine (29022-11-5) + HCl*H-Glu(OtBu)-OKb, Kb=2,4-didocosyloxybenzyl + N-Fmoc L-Phe (35661-40-6) + Fmoc-(tBu)Asp-OH (71989-14-5) + L-Asn(Trt) (132388-59-1) → HCl*H-Gly-Asn(Trt)-Gly-Asp(OtBu)-Phe-Glu(OtBu)-OKb, Kb=2,4-didocosyloxybenzyl

Conditions

Yield

Stage #1: HCl*H-Glu(OtBu)-OKb, Kb=2,4-didocosyloxybenzyl; N-Fmoc L-Phe With N-ethyl-N,N-diisopropylamine; 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride In tetrahydrofuran; N,N-dimethyl-formamide at 20℃; for 0.5h; Stage #2: With piperidine; benzotriazol-1-ol; 1,8-diazabicyclo[5.4.0]undec-7-ene In tetrahydrofuran; N,N-dimethyl-formamide at 20℃; for 0.166667h; Stage #3: N-(fluoren-9-ylmethoxycarbonyl)glycine; Fmoc-(tBu)Asp-OH; L-Asn(Trt) Further stages;

90.8%

Fmoc-Val-OH (68858-20-8) + Fmoc-Ser(tBu)-OH (71989-33-8) + Fmoc-Glu(OtBu)-OH (71989-18-9) + acetic anhydride (108-24-7) + L-Asn(Trt) (132388-59-1) → Ac-S(tBu)E(OtBu)VN(trt)-OH (1447762-81-3)

Conditions	Yield
Stage #1: L-Asn(Trt) With N-ethyl-N,N-diisopropylamine In N,N-dimethyl-formamide at 20℃; for 3.25h; Stage #2: With piperidine In N,N-dimethyl-formamide Stage #3: Fmoc-Val-OH; Fmoc-Ser(tBu)-OH; Fmoc-Glu(OtBu)-OH; acetic anhydride Further stages;	90%

(S)-2-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)-6-(dimethylamino)hexanoic acid + Fmoc-O-methyl-L-serine (159610-93-2) + N-Fmoc L-Phe (35661-40-6) + L-Asn(Trt) (132388-59-1) + N-(9-fluorenylmethoxycarbonyl)-O-methyl-L-tyrosine (77128-72-4) → HO-Phe-Tyr(Me)-Ser(Me)-Asn(Trt)-Lys(Me)2-NH2

Conditions	Yield
Stage #1: (S)-2-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)-6-(dimethylamino)hexanoic acid With N-ethyl-N,N-diisopropylamine In dichloromethane for 4h; Stage #2: With piperidine In N,N-dimethyl-formamide; isopropyl alcohol Stage #3: Fmoc-O-methyl-L-serine; N-Fmoc L-Phe; L-Asn(Trt); N-(9-fluorenylmethoxycarbonyl)-O-methyl-L-tyrosine Further stages;	90%

Upstream product

• 82911-69-1 N-(9H-fluoren-2-ylmethoxycarbonyloxy)succinimide 
• 132388-58-0 (S)-2-Amino-N-trityl-succinamic acid 
• 76-84-6 triphenylmethyl alcohol 
• 71989-16-7 Fmoc-Asn-OH 
• 107-06-2 1,2-dichloro-ethane 
• 132388-57-9 N-benzyloxycarbonyl-N'-trityl-L-asparagine 

Downstream Products

• 132388-64-8 N-α-Fmoc-N-β-trityl-L-asparagine pentafluorophenyl ester 
• 71989-16-7 Fmoc-Asn-OH 
• 132388-62-6 Fmoc-Asn(trityl) 2,4,5-trichlorophenyl ester 
• 132388-66-0 Fmoc-Asn(Trt)-ODhbt 

Relevant articles and documents

Multiple solid phase synthesis via Fmoc-amino acid fluorides

In addition to displaying high reactivity, Fmoc-amino acid fluorides are shown to be highly soluble and stable for extended periods in organic solvents such as DMF and therefore to be recommended for use in Multiple Peptide Synthesis. A series of analogs of alamethicin and a partial sequence (22 amino acids) of the CNG-channel forming protein BOVTESTIS have been assembled with excellent results.

Unwanted hydrolysis or α/β-peptide bond formation: How long should the rate-limiting coupling step take?

Nowadays, in Solid Phase Peptide Synthesis (SPPS), being either manual, automated, continuous flow or microwave-assisted, the reaction with various coupling reagents takes place via in situ active ester formation. In this study, the formation and stability of these key active esters were investigated with time-resolved 1H NMR by using the common PyBOP/DIEA and HOBt/DIC coupling reagents for both α- and β-amino acids. Parallel to the amide bond formation, the hydrolysis of the α/β-active esters, a side reaction that is a considerable efficacy limiting factor, was studied. Based on the chemical nature/constitution of the active esters, three amino acid categories were determined: (i) the rapidly hydrolyzing ones (t 24 h) in solution. The current insight into the kinetics of this key hydrolysis side reaction serves as a guide to optimize the coupling conditions of α- and β-amino acids, thereby saving time and minimizing the amounts of reagents and amino acids to be used-all key factors of more environmentally friendly chemistry.

NOVEL PEPTIDES DERIVED FROM NCAM (FGLs)

The present invention relates to novel compounds comprising at most 13 contiguous amino acid residues derived from the fibronectin type 3,I1 module of neural cell adhesion molecule (NCAM), or a variant or fragment thereof, capable of interacting with an FGFR and thereby the compounds are capable of inducing differentiation, modulating proliferation, stimulate regeneration, neuronal plasticity and/or survival of cells. Further, the present invention relates to the use of said compounds for production of a medicament for treatment of conditions and diseases, wherein NCAM and/or FGFR play a prominent role.

Derivates of Polyethylene Glycol Modified Thymosin Alpha 1

Pharmaceutical compositions that include thymosin alpha 1 peptide derivatives modified at the C-terminal of the peptide chain with polyethylene glycol, and their pharmaceutical acceptable salts, are generally disclosed. Also, new methods used to prepare these thymosin alpha 1 peptide derivatives modified at the C-terminal of the peptide chain with polyethylene glycol are generally provided. The presently disclosed compounds and their salts can be prepared administered to humans to treat immune disease and can also be used in adjuvant treatment.

GLP-2 compounds, formulations, and uses thereof

The present invention relates to novel human glucagon-like peptide-2 (GLP-2) peptides and human glucagon-like peptide-2 derivatives which have a protracted profile of action as well as polynucleotide constructs encoding such peptides, vectors and host cells comprising and expressing the polynucleotide, pharmaceutical compositions, uses and methods of treatment.

Protected amino acids and process for the preparation thereof

Compounds of the formula I, STR1 in which 'R1 is an amino protective group, and n stands for 1 or 2, R1 denotes hydrogen or an amino protective group, R2 denotes hydrogen or a carboxyl protective group and R3 denotes triphenylmethyl, 4-monomethoxy-trityl or 4,4'-dimethoxy-trityl, and reactive carboxylic acid derivatives of such compounds of the formula I in which R2 stands for hydrogen, are described. These compounds can be used as starting materials for the preparation of peptides. They are more suitable for this than are analogous compounds of the formula I in which R3 denotes hydrogen or one of the carbamoyl protective groups hitherto customary.

Protection of carboxamide functions by the trityl residue. Application to peptide synthesis

Carboxamide functions may be tritylated by an acid-catalyzed reaction with triphenylmethanol and acetic anhydride in glacial acetic acid. The ω-trityl group of asparagine and glutamine is cleavable by TFA, but stable to strong mineral acids in aqueous solution, as well as to nucleophiles and bases. In peptide syntheses, it is ideally suited for combination with side-chain protections of the t.butyl-type.