Acids, cyclopropyl-substituted

It is worth mentioning here that the spirocyclopropyl-substituted oxazoline-5-car-boxylates 2-172, as well as the corresponding thiazoline-4-carboxylates, can be transformed into cyclopropyl-substituted amino acids, which might act as potential enzyme inhibitors [93] and interesting building blocks for peptidomimetics [94]. 

Reaction of 2,3-dichloroquinoxaline 367 with sodium azide in ethanol has been used to synthesize bistetrazolo-[l,5- 5, l -c]quinoxaline 368 in 65% yield (Scheme 28) <1997JOC4082>. Similarly, reaction of 2,3-dichloroquinoxaline 367 with thiosemicarbazide 366 has been used to generate l,6-diamino-bis-l,2,4-triazolo[4,3- 3,4-f]quinoxaline 365 in 67% yield <2002AP389>. Condensation of cyclopropanecarboxylic acid hydrazide 369 meanwhile gives rise to the cyclopropyl-substituted tetracycle 370 in 93% yield in the presence of l,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as base (Scheme 28) <2005JOC2878>. 

A single product is also formed in the case of unsymmetrical ketones of the MeCOCHR R2 or RCH2COCHR R2 type, since for the Pfitzinger reaction to occur the ketone must contain either a methyl group or a methylene group next to the carbonyl group. For example, only one appropriate cyclopropyl-substituted acid 16 is formed from methyl cyclopropyl ketone 15 and isatins 9 [23, 24],... 

The results with cyclopropyl-substituted amines also reveal the operation of several effects. Cyclopropylamine (5) is significantly less basic than cyclohexylamine in solution , as expected due to -withdrawal from the protonated ammonium ion. However, there is also evidence for significant stabilization of the free amine by u-electron donation to cyclopropyl (see Section III.D) so the resultant low basicity is evidently due to a combination of these effects, which operate in the same direction. p-Cyclopropylaniline is somewhat more basic than the p-isopropyl analog S and this effect evidently arises from 7c-donation to the ring, stabilizing the protonated conjugate acid. The gas phase basicity of 5 is discussed in Section V.I. 

Esposito, A., Piras, P. P., Ramazzotti, D., Taddei, M. First Stereocontrolled Synthesis of (S)-Cleonin and Related Cyclopropyl-Substituted Amino Acids. Org. Lett. 2001, 3, 3273-3275. 

Most reactions resulting in water elimination have been carried out using cyclopropyl-substituted alcohols under acidic or close to neutral conditions ° 1131,1134.1170,1171,1185.1606,1664,1674,1712,1764-1770 OJby usingiodine in benzene," phos-... 

Pentacarbonyl[cyclopropylethynyl(ethoxy)carbene]chromium complex 19 reacted with cyclo-penta-1,3-diene to give a cyclopropyl-substituted carbene complex of norbornadiene 22, which was converted to the corresponding carboxylic acid 23 upon oxidation or to a 1,4-quinone-type derivative 24 after Dotz-type cyclization with phenylethyne. ... 

Ruthenium(II)-mediated oxidative annulation reaction of benzoic acids and cyclopropylarylethynes furnishes a mixture of 3- and 4-cyclopropyl substituted isocoumarins (130BC142).A facile one-pot synthesis of4-aryl-isocoumarins involves an acidic hydrolysis of ( -2-(l-aryl-2-methoxy-ethenyl)benzaldehydes with HBr and subsequent oxidation with PCC (13HCA2173). 

Likewise, Et(Cl)C=N =NR and R R C=N+=NC(C1)R R" react with nitriles to give the [3+2] cycloadductsSugar nitriles react with l-(chloroalkyl)-l-aza-2-azoniaallene salts in the presence of Lewis acids to give the expected cycloadducts Also, cyclopropyl substituted l-aza-2-azoniaallene salts 46 react with acetonitrile to form mixtures of [3+2] cycloadducts 47 and 48. ... 

Substitution of the -methyl group of penicillanic acid sulfone has also been extensively investigated. The cyclopropyl sulfone (25, R = R = H,... 

Direct interception of the initially formed bicyclic oxyallyl zwitterion derived from cyclohexadienones is difficult, due to its facile rearrangement to cyclopropyl ketone. One notable exception is the observation that 4-trichloromethyl-substituted dienone 94 gave solvent adduct 97 when irradiated in methanol, and both 97 and 98 upon irradiation in acidic methanol (Scheme 24)48. It was proposed that 97 arises either from a facile... 

The ring closure of N-isopropyl- or /V-cyclopropyl-A/-(substituted phenyl Jaminomethylenemalonates (785) in polyphosphoric acid at 100-110°C for 1 hr gave quinoline-3-carboxylates (786) in good yields (85JAP(K)28964, 85JAP(K)126271). 

A-cyclopropyl- and N- Xhy -N-(substituted phenyl)aminomethylene-malonates were cyclized in polyphosphoric acid [89EUP332033, 89JAP(K)83068], in ethyl polyphosphate (89USP479490), and in phospho-ryl chloride (89EUP304158). 

Besides the large number of a-amino acids found in nature, )3-amino acids are gaining an ever increasing attention [100]. Amino acids are e.g. found in the side chain of the cancerostatic taxol [101] as well as the new antibiotics sperabillin and TAN 1057 A/B [102]. The simple deprotection of 2 -substituted cyclopropylacetic acid derivatives 196-R by hydrogenolysis (and hydrolysis for the methyl esters 196b,i,j,m-Me) yielded enantiomerically pure 2-(r-amino-cyclopropyl)acetic acids (Scheme 59) [10]. 

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