Excess mixed anhydride peptide synthesis with histidine derivatives

Abstract

Anhydrous HCI was bubbled through 25 ml of purified HMPA for 25 min. at such a rate that the temperature reached 700 after 4 min. It was then kept between 67-73" for another 21 min. 2 ml of the reaction mixture were taken out as fraction I.The HCI flow was now decreased and the reaction mixture heated to about 16CP for 44 hours. The cooled down mixture was then extracted with 3 x 100 ml of ether. Small amounts of NHMe,.HCI in the ether fraction was filtered off and the ether evaporated. The remaining mixture was fraction 11.A GLC-spectrum (5 % SE-30 DMCS column) of fraction I showed that it contained HMPA and P(O)CI(NMe,), in an approximate ratio of 1 : 2. No peak belonging to P(O)CI,NMe, was found. Further identification was performed by NMR, where the J,, from P(O)(NMe,), was found to be 9.5 Hz [lit. Is: J,, = 9.5 Hz (in CCI,)] and the J,, from P(O)CI(NMe,), was 13.0 Hz [lit. 14: J,, = 13.0 Hz (in CCI,)]. A GLC-spectrum (the same column as for fraction I) of fraction I1 showed that it contained only P(O)CI(NMe,), and P(O)CI,NMe, in an approximate ratio of 5 : 2. No P(O)CI, was found. In a NMRspectrum of the mixture J,, from P(O)CI(NMe,), was found to be 13.0 Hz and J,, from P(O)CI,NMe, was found to be 16.0 Hz [lit. 14: J,, = 15.8 (in CCI,)].Abstract. The coupling of histidine derivatives by the excess mixed anhydride method was investigated with respect to the yield, the racemization, and the formation of by-products. The tert-butyloxycarbonyl-(Boc-), isobutyloxycarbonyl-(i-Boc-), benzyloxycsrbonyl-(Z-), and p-toluenesulfonyl-(Tos-) groups were found to be suitable for protection of the imidazole nucleus.A new way of selective removal of the Ni,-Tos group, with pyridine hydrochloride, is described.

Unified Synthesis and Biological Evaluation of Makaluvamine J and Its Analogs

“…In the first attempt, the Ts-protecting group was removed, followed by N-methylation to prepare makaluvamine P (10). Pyridine hydrochloride in DMF [26] was identified as the optimal reagent for removing the Ts group, yielding makaluvamine D (5) in a good yield. Other attempted detosylation conditions (Cs 2 CO 3 in THF/MeOH [27], NaH in DMF [28], and TFA/Me 2 S [29]) were not effective.…”

Solution‐Phase Peptide Synthesis

“…with tosyl chloride [197,198]. It is also removed by 1 M NaOH and partially removed by triethylamine in organic solvent or N-hydroxybenzotriazole [197,198]. It is also removed by 1 M NaOH and partially removed by triethylamine in organic solvent or N-hydroxybenzotriazole [197,198].…”

Development of a competitive lateral flow immunoassay for progesterone: influence of coating conjugates and buffer components

“…Conjugates of P4-HS to PE 2 -biotin or PE 3 -biotin (Pierce, Perbio Science Nederland, Etten-Leur, the Netherlands) were prepared by the mixed anhydride method [12] with minor modifications. P4-HS-PE 2 -biotin and P4-HS-PE 3 -biotin conjugates were purified using a preparative HPLC system with mass detection (Waters Corp., Milford, MA, USA) and fractions with the required mass were lyophilised.…”