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Studies in the Flavin Series . Part X V P Alkylation and Rearrangement React ions of Di hyd roalloxazines
| Content Provider | Semantic Scholar |
|---|---|
| Author | Jefcoate, Colin R. Ghisla, Sandro Hemmerich |
| Abstract | Alkylation of 5-acetyl-5.1 O-dihydro-1.3.7.8-tetramethylalloxazine (2) in dimethylformamide proceeded at the bridge position C(4a) or at N(10) to an extent dependent upon the alkylating agent. An increasing tendency for substitution at C(4a) in the order dimethyl sulphate < methyl iodide 4 allyl bromide c benzyl bromide was found, and was interpreted as representing a trend from a hard to a soft electrophile. The relative reactivities indicated that C(4a) was a soft nucleophilic centre whereas N(10) was a hard centre. The bending of dihydro(iso)allox-azines about the N(5)-N(10) axis is considered to have an important influence on the reactivities at N(10) and C(4a). 5-Deacetylation resulted in migration of an allyl or benzyl substituent from N(10) to C(4a) ; the derivatives with a saturated alkyl group a t N(10) did not show this migration. THE chemistry of dihydro(iso)alloxazines-1 has remained largely unexplored, in spite of their biological significance as the fully reduced state of flavocoenzymes. However, the present knowledge of fully reduced flavins has recently been reviewed.2 Flavin-dependent sub-strate dehydrogenations involve a two-electron transfer, which is thought to occur as a ' hydride transfer' [reaction (i)], but could alternatively be considered formally as a transfer of R-, with subsequent proton-ation of a covalent R-F1 (alkyl-flavin) intermediate [reaction (ii)]. In the case of reaction (i), the possibility \R-Fl-,d + H+ __t HFl-red + R+ (ii) also exists that an interaction of FlH-,,d with R+ may contribute significantly to the reaction path. Thus flavin-dependent dehydrogenations require. an understanding of the nature of group transfer. This can be experimentally approached by the characterisation of reactive ' alkyl-flavin ' intermediates. For this reason, our group has studied the alkylation reactions of di-hydro (iso) alloxazines. It was previously shown that alkylation of |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | https://kops.uni-konstanz.de/bitstream/handle/123456789/9835/jefcoate_ghisla_hemmerich_alkylation_1971.pdf?isAllowed=y&sequence=1 |
| Alternate Webpage(s) | http://kops.uni-konstanz.de/bitstream/handle/123456789/9835/jefcoate_ghisla_hemmerich_alkylation_1971.pdf?isAllowed=y&sequence=1 |
| Language | English |
| Access Restriction | Open |
| Subject Keyword | 4,6-dinitro-o-cresol Alkylating Agents Alkylation Apache Axis Axis vertebra Bromides Covalent Interaction Decompression Sickness Dimethyl Adipimidate Dimethylformamide Electron Transport Experiment Flavins H+: The Digital Series Iodides Ions Isoproterenol Ploidies Protons R language Sulfate measurement adenotonsillectomy alkyl allyl bromide benzyl bromide methyl iodide |
| Content Type | Text |
| Resource Type | Article |
