49822-58-4Relevant academic research and scientific papers
Extending pummerer reaction chemistry: Application to the assembly of the pentacyclic core of dibromopalau'amine
Feldman, Ken S.,Nuriye, Ahmed Yimam
scheme or table, p. 4532 - 4535 (2010/12/25)
A pentacyclic model system featuring the trans azabicyclo[3.3.0]octane unit of dibromopalau'amine was prepared with complete diastereoselectivity in the polycyclic core from a tricyclic precursor. The key transformations of this sequence include (a) a Pum
Further Studies on the Protection of Histidine Side Chains in Peptide Synthesis: The Use of the ?-Benzyloxymethyl Group
Brown, Tom,Jones, John H.,Richards, John D.
, p. 1553 - 1562 (2007/10/02)
Further studies on the use in peptide synthesis of N(?)-phenacyl protection for histidine side chains have shown that whilst this prevents the side chain-induced racemization which can occur if there is a lone pair of electrons available at the ?-nitrogen, there are concomitant drawbacks.As an alternative approach to the racemisation problem, the effect of halogenation of the heterocyclic ring carbons (to diminish the availability of the ?-nitrogen lone pair) has been investigated.This gives derivatives which are convenient in both classical and solid-phase applications, the halogen modifying groups being removed at the last stage by catalytic hydrogenolysis over a rhodium catalyst.Racemization is suppressed as expected, but it is not eleminated completely: direct blockade of the ?-nitrogen appears to be indispensable for its complete prohibition.Protection of the ?-nitrogen with a benzyloxymethyl group has now been found to be much more satisfactory than the use of the phenacyl group for this purpose.A ?-benzyloxymethyl substituent not only prohibits side chain-induced racemisation but also gives derivatives with convenient physical properties which can be incorporated into well estblished classical and solid-phase strategies without the need for any novel or additional operations or changes in protocol.The protecting group is stable to basic conditions, to trifluoroacetic acid, and to aqueous solutions of carboxylic acids, but is cleaved cleanly and rapidly by hydrogen bromide in trifluoroacetic acid or by catalytic hydrogenolysis.N(α)-t-Butoxycarbonyl-N(?)-benzyloxymethyl-L-histidine has been prepared in good yield by a simple procedure from an easily accessible intermediate and isolated as a crystalline solid; its use has been demonstrated by a number of exercises including a solid-phase synthesis of 5-isoleucine-angiotensin II and a classical synthesis of trihistidine.
Analgesic imidazolemethanols
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, (2008/06/13)
α,α-Diarylimidazole-2-methanols of the general formula STR1 wherein R1 -R10 are the same or different and each represents a hydrogen or halogen atom or a trifluoromethyl or tertiary butyl group, with at least one of said R1 -R10 being halogen, trifluoromethyl or tertiary butyl; R11 and R12 are the same or different and each represents a hydrogen atom, an alkyl group, a phenyl group or a halogen-or trifluoromethyl-substituted phenyl group; and R13 represents a hydrogen atom or a lower alkyl group, a lower alkoxymethyl group, a phenylalkyl group (optionally substituted in the phenyl moiety by one or more halogen atoms or alkyl or trifluoromethyl groups), an alkenyl group, a phenyl(lower)alkoxymethyl group (optionally substituted in the phenyl moiety by one or more halogen atoms or alkyl or trifluoromethyl groups) or a benzenesulfonyl group (in which the phenyl moiety is optionally substituted by one or more alkyl groups) are described. These compounds and their non-toxic acid addition salts have anorexient activity. Certain of these compounds have analgesic activity comparable to morphine but without its serious side effects. Processes for their manufacture and compositions for their use are described.
