Reaction of 2,5‐diisopropyl‐ and 2,5‐di‐sec‐butylpyrazine 1‐oxide. Derivatives with phosphoryl chloride and acetic anhydride

Abstract

In order to examine the α‐substitution of side chains, various derivatives of 2,5‐diisopropyl‐ and 2,5‐disec‐butylpyrazine 1‐oxides were subjected to the reaction with phosphoryl chloride and acetic anhydride. Chlorination and acetoxylation were recognized to take place on the pyrazine ring in almost all cases.

Rearrangement of N-Oxyenamines and Related Reactions

“…During Boekelheide rearrangements double-bond formation can be observed instead of acyloxy group migration as just discussed. ,− A mechanism involving abstraction of a proton from cation C (see Scheme ) rather than the [3,3]-rearrangement–elimination sequence cannot be excluded. For instance, the tetrahydrofuran derivative 327 afforded the furan 328 under reflux in acetic anhydride (Scheme ) .…”

“…Thus, while reaction of 2- n -butyl-pyrazine N -oxide proceeds smoothly, reaction of the 2-benzyl derivative 329 affords significant amounts of the core substitution product 330 (Scheme ) . For the isobutyl substituent and other branched alkyl groups, yields of the normal rearrangement products are quite low.…”

“…The same approach was used for the transformation of pyridines, − oxazoles, , and benzisoxazoles . Achievement of high yields requires addition of base, which abstracts a proton from the intermediate complex 343 . , In the absence of base nucleophilic substitution occurs at positions 2 and 4. ,,, However, there are examples of selective chlorination of the side chain . Useful reagents are di- and triphosgene .…”

Bioactive 2(1H)-Pyrazinones and Diketopiperazine Alkaloids from a Tunicate-Derived Actinomycete Streptomyces sp.

“…Compound 6 was reported before as 2-hydroxy-3,6-di- sec -butylpyrazine and was identified by mass spectroscopy only [23,24,25,26]. To the best of our knowledge, there is no available complete NMR data for compound 6 .…”

“…Bioassay-guided fractionation of the active fractions of an organic extract of this strain resulted in the isolation and identification of three new alkylated 2(1 H )-pyrazinone derivatives including ( S )-6-( sec -butyl)-3-isopropylpyrazin-2(1 H )-one ( 1 ), ( S )-3-( sec -butyl)-6-isopropylpyrazin- 2(1 H )-one ( 2 ) and ( S )-6-( sec -butyl)-3-isobutylpyrazin-2(1 H )-one ( 3 ), together with deoxymutaaspergillic acid ( 4 ) [10,11,12,13,14,15,16], 3,6-diisobutyl-2(1 H )-pyrazinone ( 5 ) [15,16,17,18,19,20,21,22,23] and 3,6-di- sec -butyl-2(1 H )-pyrazinone ( 6 ). Compound 6 was published before as 2-hydroxy-3,6-di- sec -butylpyrazine [23,24,25,26]. In addition, four diketopiperazine alkaloids including cyclo(6-OH- d -Pro- l -Phe) ( 7 ) [27], bacillusamide B ( 8 ) [28], cyclo( l -Pro- l -Leu) ( 9 ) [29] and cyclo( l -Pro- l -Ile) ( 10 ) [30] were isolated from the extract of the marine Streptomyces sp.…”