Analysis cyclic imine

Stereoselective addition of a chiral cyclic phosphite to a cyclic imine was applied to the synthesis of phosphonic analogs of d- and L-penicillamine41. Enantiomerically pure dioxaphospholane oxide 6 underwent addition to 2,5-dihydro-2,2,5,5-tetramethylthiazole in the presence of boron trifluoride as a catalyst. The diastereomeric adducts 7, obtained in a 2 1 ratio, were easily separated on silica gel and their configuration assigned by X-ray analysis the (4/ )-isomer was shown to be the major diastereomer. Hydrolysis of each diastereomer gave pure enantiomers of phosphopenicillamine 841. 

Spiro-prorocentrimine (196) is a polar lipid-soluble toxin isolated from a laboratory-cultured benthic P. lima collected in Taiwan. It was crystallized in methanol and X-ray diffraction analysis of spiro-prorocentrimine (196) revealed a spiro-linked cyclic imine with the 1,1,2,4-tetrasubstituted 3-cyclohexene in addition to its macrolide skeleton. Biogenetically, prorocentrolides and spiro-prorocentrimine might be related to each other. 

Chemical analysis of contaminated oysters revealed the presence of a new toxin, gymnodimine, which was shown to be a cyclic imine [4-6]. This same substance was obtained from cultures of K. selliformis, confirming that this organism is a source of the toxin in New Zealand [4,5]. No other gymnodimine-producing organisms have yet been identified. 

A retrosynthetic analysis of 24 using an MCR sequence is presented in Scheme 15.8. The required starting materials for the key Ugi-type 3CR were the carboxylic acid 25, cyclic imine 26, and isocyanide 28. The acid 25 could be accessed by standard peptide chemistry, while imine 26 was generated in situ from the commercially available 27 by catalytic oxidation with the enzyme MAO-N (monoamine oxidase N) from Aspergillus niger. The isocyanide 28 was accessed via a Passerini three-component reaction (P-3CR) of 29,30, and acetic acid. 

The above cycloaddition process consists of two separate [3-1-2] cycloaddition steps and represents a 1,3-2,4 addition of a multiple bond system to a hetero-1,3-diene [7S7]. The structure ot the azomethine imine intermediate has been proved unequivocally by X-ray analysis [195] Ethylene [194], acetylene [/iS2] . many alkyl- and aryl- as well sgemmal dialkyl- and diaryl-substituted alkenes [196,197, 198, 199], dienes [200], and alkynes [182, 201], certain cyclic alkenes [198, 199,... 

The preferred tautomer of the products derived from the condensation reaction of phenylenediamine with cyclic /3-keto esters (Scheme 5) is highly dependent on the structure of the /3-ketoester <2005JHC1001>. H and 13C NMR analysis of the l,5-benzodiazepin-2-one 34, formed from methyl 2-oxocyclohexanecarboxylate under micro-wave conditions, indicated the presence of the C(4)-N(5) imine <2005JHC1001>. In contrast, the products arising from condensation with methyl 2-oxocyclopentanecarboxylate and methyl l-alkyl-4-oxopiperidine-3-carboxylates were found to be in the enamine form 35. 

A special situation arises when mercaptosuccinic acid is used as a mercapto component. Both the carboxyl functions are prone to nucleophilic attack by the imine nitrogen and give rise to five- (I) as well as six-membered (II) cyclic structures. Subsequently, Poop et al. showed by X-ray crystal structure analysis that a five-membered (III) cyclic structure is preferred over the six-membered (IV) cyclic structures (Scheme 8) [30]. 

OXAM, A/,A/ -dimesityloxalamidinate Xyl, 2,6-dimethylphenyl DiPP, 2,6-diisopropylphenyl BQI, benzoquinone imine pzR, 3-alkylpyrazolate PZR2, 3,5-dialkylpyrazolate A, elemental analysis m/d, melting or decomposition point MS mass spectrum UV, ultravlolet-visible IR Infrared H, " C, P, F, NMR spectra XR X-ray diffraction CV, cyclic voltammetry. 

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