Two mutagenic compounds have been isolated and purified from commercial beef extract. These two compounds have chemical, chromatographic, spectroscopic and biological behavior indistinguishable from those of the two known mutagens 2-amino-3-methyl-imidazo-[4,5-f]-quinoline and 2-amino-3,8-dimethyl-imidazo-[4,5-f]-quinoxaline.
SummaryProximity effects alone as well as in combination with electronic effects are responsible for the observed phenomenon of base-catalyzed ether formation initiated by nucleophilic attack on a C,C double bond of the tricyclic olefin alcohols 1-10 (Scheme I , Table I ) .With compounds 1-4, bearing a keto group, formation of the ethers 11-14 proceeds through a corresponding homoenolate b (Scheme 2) as an intermediate.
In one case such a species could be trapped as the methyl ether 21 (Scheme 3).Special attention is given to the stereochemical course of the homoketonization. Ring opening in 21 under acidic conditions occurs regioselectively, however non-stereoselectively (Scheme 3). Full regio-and stereoselectivity (retention) is observed under basic conditions starting from the unsaturated keto alcohols 1 and 2 (Scheme 4) as well as from the keto ethers 11 and 12 (Scheme 5, Table 2).We recently observed base-catalyzed ether formation with polycyclic olefin alcohols [ 11. As part of our systematic investigation of this phenomenon2) we studied the behaviour of the alcohols 1-lo3) (see Scheme I and Table I ) . The results allow us to distinguish two main driving forces: a proximity effect and an electronic effect.Steric compression is the sole responsible cause for the observed unusual nucleophilic attack on the isolated C,C double bond in 7 ( 4 17), 8 (+ 18) and 10 ( 4 20). A methyl group at the carbon atom bearing the hydroxyl group enhances the reactivity (compare 2 vs. 1, 4 vs. 3, 6 vs. 5, 8 vs. 7, 10 vs. 9), whereas ring enlargement (X = CH2-CH2-CH2) lowers it (compare 9 vs. 7,lO vs. 8).
An enantioselective synthesis of the potent angiotensin-converting enzyme inhibitor (I'S,3S)-3-[( 1'-(ethoxycarbonyl)-3'-phenylpropyl)amino]-2,3,4,5-tetrahydro-2-0~0-1~~ I-benzazepine-I-acetic acid hydrochloride (3) is described which uses a crystallization-based resolution of a racemic amino intermediate with concomitant racemization ofthe unwanted enantiomer.
SummaryThe title compound 1 is a further example of an olefinic alcohol that undergoes ether formation under basic conditions ( 4 3 ) although the double bond is not activated by an electron-attracting group. This unusual reactivity is due to steric compression, which is increased in the 10-methyl analogue 2. This forms the corresponding ether 7 at a much higher rate. -In a deuteriated medium, base-catalysed cyclization of 1 gives the exo-deuteriated ether 6, corresponding to trans-addition. -An X-ray structure analysis of 4, thep-nitrobenzoate of 1, is presented.Very recently we reported about the ability of several olefinic alcohols of the general type a to undergo ether formation to b under basic conditions [2] (see Scheme I ) . This uncommon reactivity is mainly due to high steric compression, which is more pronounced in compounds with R ' = CH instead of H.
Tricyclic olefinic alcohols containing an unsymmetrically alkyl‐substituted C, C‐double bond were cyclized intramolecularly to their corresponding ethers under basic conditions: 9 → 12, 10 → 17 + 18, and 11 → 12 (Scheme 3, Table 1). The reactivity is mainly due to relieve of ground state strain.
Alcohol 9 (endocyclic double bond) isomerized under intramolecular assistance by the hydroxyl group to 11 (exocyclic double bond) before cyclization to 12 occurred (Scheme 5). The latter step being the faster one, no isomerization 11 → 9 was observed.
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