Synthesis of Carboxyl Terminal Segments of Beta‐subunit of Human Chorionic Gonadotropin

Rolli, Hanspeter; Blaser, Kurt; Pfeuti, Christiane; Schneider, Conrad H.

doi:10.1111/j.1399-3011.1980.tb02915.x

International Journal of Peptide and Protein Research

1980

DOI: 10.1111/j.1399-3011.1980.tb02915.x

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Synthesis of Carboxyl Terminal Segments of Beta‐subunit of Human Chorionic Gonadotropin

Hanspeter Rolli

Kurt Blaser

Christiane Pfeuti

et al.

Abstract: The synthesis in solution of carboxyl terminal peptide segments of the beta‐subunit of human chorionic gonadotropin is described. The protected segments include sequences 119–131, 132–137, and 138–145. The syntheses were based on a standardized liquid‐liquid extraction program for routine purification of intermediates (two‐phase method). Condensation of terminally deblocked segments afforded protected peptides 132–145, 126–145, 120–145 and 119–145. Protected peptides 126–145 and 120–145 were deprotected in liq… Show more

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Cited by 8 publications

References 13 publications

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Deblocking ofo‐Nitrophenylsulfenyl‐Protected Peptides by Ammonium Thiocyanate and (2‐Methyl‐1‐indolyl)acetic acid

Lüscher

Schneider

1983

Helvetica Chimica Acta

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SummaryThe thiocyanate cleavage of the N"-o-nitrophenylsulfenyl group from peptides in solution or on a solid support proceeds effectively in the presence of (2-methyl-1 -indolyl)acetic acid. This scavenger was prepared from 2-methylindole and sodium bromoacetate; it can readily be removed by extraction with base after the cleavage reaction, together with (2-methyl-3-(2-nitrophenylthio)-1 -indolyl)acetic acid.The o-nitrophenylsulfenyl (Nps) group introduced into peptide synthesis by Zervas et al. [ 11 has considerable potentialities as a temporary protecting group for the a -amino terminus because its selective removal can be accomplished by nucleophilic reagents. These reagents avoid problems encountered with protecting groups requiring acids for their cleavage, i.e. alkylation of the side chains of methionine, tyrosine and also lysine and histidine by carbocations or their reaction products with the deprotecting reagent (e.g. t-butyl trifluoroacetate) [2]. Thiolytic cleavage of the Nps group with a number of reagents has been described, and recently 2-mercaptopyridine was shown to enable rapid deprotection 131 [4].In our hands the method of Wunsch & Spangenberg [ 5 ] using thiocyanate (rhodanide) in the presence of 2-methylindole proved very valuable for the cleavage of Nps-protected peptides. Thiocyanate ion attacks N-terminally bound Nps and reversibly forms o-nitrophenylsulfenyl thiocyanate (1). The equilibrium is fully displaced in the presence of excess 2-methylindole since 1 is converted into stable 3-(2-nitrophenylthio)-2-methylindole (2) and thiocyanate ion. The indole derivative is removed by washing with ether. However, with relatively lipophilic peptides, ether extraction becomes unsatisfactory. Since the two-phase-purification method of peptide synthesis [6] [7] frequently used in our laboratory depends on lipophilic peptide intermediates, it seemed worthwhile to adapt the indole reagent used in [5] and to investigate carboxy derivatives of indole which can be removed by aqueous base after reaction with an Nps residue.Using Nps-Lys(Boc)-OH as a model, the cleavage rate of a variety of reagents was assessed (Table I). It is obvious that the 3-position of the indole system should be reserved for the Nps capture and cannot be blocked as in the indoles 3-5. The

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Deblocking ofo‐Nitrophenylsulfenyl‐Protected Peptides by Ammonium Thiocyanate and (2‐Methyl‐1‐indolyl)acetic acid

Lüscher

Schneider

1983

Helvetica Chimica Acta

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(Cholestanyloxycarbonyl)benzyl esters as peptide substituents: Conformational properties of fully protected oligo‐L‐lysines with C‐terminal (cholestanyloxycarbonyl)benzyl and benzyl ester moieties

Toniolo

Bonora

Moretto

et al. 1986

Helvetica Chimica Acta

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This study involves L-lysine oligo peptides, protected at the N-terminus by the Nps and at the &-amino functions by Boc groups. Two series were prepared from dimer to octamer, one containing the p-[(cholestan-3/3-yloxy)carbonyl]benzyl, the other one the benzyl ester group at the C-terminus. Conformational analyses were performed by IR absorption. The occurrence of the intermolecular [i-structure in the solid state and in CHzC1, solution was demonstrated for the highest oligomers. The relative stabilities of the self-associated species were determined by adding a variety of polar solvents to the CHzC12 solutions. The cholestanyl-containing peptides have a lower propensity to self-aggregate than the bcnzyl-ester analogues. Self-aggregation and decreasing solubility run in parallel. It was also directly shown that soluble urea derivatives may disrupt intermolecular H-bonds in CH2CIz, a point of practical interest, particularly in solid-phase peptide synthesis.Introduction. ~ C-Terminal protecting groups containing the cholestanol moiety are promising tools in the synthesis and conformational analysis of peptides, since they enhance peptide solubilities in organic solvents of low polarity [ 1-51. In previous work, p -([4-(cholestan-3~-yloxy)succinyloxy]methyl} benzyl ( = Chsucb (formerly Suco)) peptide esters were mainly used, but their preparation is rather cumbersome. Therefore, other carboxyl substituents containing cholestanol were proposed [6], inter afia the p-[(cholestan-3P-yloxy)carbonyl]benzyl ( = Chocb (formerly Beco)) ester group. In the present communication, we describe two complete series of [Lys( Boc)], peptides with n = 2 to 8, both carrying at the N-terminus the Nps protecting group. At the C-terminus,

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Dependence of benzyl alcohol loss onC‐terminal amino acid in tandem mass spectrometry ofN‐protected tripeptides

Schwartz¹,

Erickson²,

Bursey³

et al. 1993

Org. Mass Spectrom.

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The effect of the basicity and chain length of the C-terminal amino acid on the fragmentation of N-protected tripeptides was investigated with a hybrid tandem instrument. Positive-ion unimolecular decomposition and colisionally activated decomposition studies on the IM + HI ' ions of a series of N-benzyloxycarbonyl (Cbz or Z)protected tripeptides, Cbz-Gly-LewXxx-OMe and Cbz-Gly-Prc+Xxx-OMe, where Xxx = Arg, Lys, Om, Gln and Glu, indicate that substitution of leucine with proline at the second position in the tripeptides facilitates the loss of benzyl alcohol (108 u) from the precursor. Additionally, higher gas-phase basicity and longer chain length of the C-terminal side-chain group promote the formation of the I M + H -1081 ' ion.

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Synthesis of Carboxyl Terminal Segments of Beta‐subunit of Human Chorionic Gonadotropin

Cited by 8 publications

References 13 publications

Deblocking ofo‐Nitrophenylsulfenyl‐Protected Peptides by Ammonium Thiocyanate and (2‐Methyl‐1‐indolyl)acetic acid

Deblocking ofo‐Nitrophenylsulfenyl‐Protected Peptides by Ammonium Thiocyanate and (2‐Methyl‐1‐indolyl)acetic acid

(Cholestanyloxycarbonyl)benzyl esters as peptide substituents: Conformational properties of fully protected oligo‐L‐lysines with C‐terminal (cholestanyloxycarbonyl)benzyl and benzyl ester moieties

Dependence of benzyl alcohol loss onC‐terminal amino acid in tandem mass spectrometry ofN‐protected tripeptides

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