0000000000161300
AUTHOR
Tamás A. Martinek
Synthesis and conformational analysis of tetrahydroisoquinoline- and piperidine-fused 1,3,4,2-oxadiazaphosphinanes, new ring systems
Abstract Through cyclization of tetrahydroisoquinoline and piperidine 1,2-hydrazino alcohols with phenylphosphonic dichloride and phenyl dichlorophosphate, P-epimeric diastereomers of 1,6,7,11b-tetrahydro-4H-1,3,4,2-oxadiazaphosphino[5,4-a]isoquinoline-3-oxides ( 13 and 14 ), 1,6,11,11a-tetrahydro-4H-1,3,4,2-oxadiazaphosphino[4,5-b]isoquinoline-3-oxides ( 15 and 16 ) and 1,6,7,8,9,9a-hexahydro-4H-pyrido[1,2-d][1,3,4,2]oxadiazaphosphinane-3-oxides ( 17 and 18 ), the first representatives of these ring systems, were prepared. NMR and X-ray diffraction studies revealed that, independently of the P-substituent and the relative configuration of the phosphorus atom, 13 , 14 , 17 and 18 could be c…
Regio- and stereoselective synthesis of constrained enantiomeric β-amino acid derivatives
Abstract Chlorosulfonyl isocyanate addition to (−)- and (+)-apopinene furnished monoterpene-fused β-lactams in highly regio- and stereospecific reactions. β-Lactams 5 and 13 exhibited reactivities similar to those of the cycloalkane-fused analogs and were easily converted to the β-amino acid and its protected derivatives. The base-catalyzed isomerization of the cis -amino ester afforded the corresponding trans -amino acid enantiomers in excellent yields. The complete isomerization is explained by the stability difference, which was estimated by ab initio calculations between the cis- and trans -diastereomers.
Facile Regio- and Diastereoselective Syntheses of Hydroxylated2-Aminocyclohexanecarboxylic Acids
By means of total regio- and diastereoselective functionalizations of cis- and trans-2-amino-4-cyclohexenecarboxylic acid derivatives 1, 9, 12 and 16, isomers of 2-amino-4-hydroxycyclohexanecarboxylic acid 8 and 11, and 2-amino-5-hydroxycyclohexanecarboxylic acid 15 and 19 were prepared in good yields, via 1,3-oxazine or γ-lactone intermediates. The enantiomers of 8 and 15 were also prepared by the same pathway, resulting in products with ee > 99 %. The structures, stereochemistry and relative configurations of the synthesized compounds were proved by NMR, using some key vicinal couplings and characteristic NOEs. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Regio- and stereoselective synthesis of the enantiomers of monoterpene-based β-amino acid derivatives
Abstract The regio- and stereospecific addition of chlorosulfonyl isocyanate to cis-δ-pinene enantiomers has furnished monoterpene-fused β-lactams. The observed regioselectivity can be explained by ab initio DFT modeling of transition state structures. In contrast with the less reactive α-pinane-fused β-lactam 4, the resulting β-lactams 5 and 13 containing an amino group connected to a secondary carbon possess similar reactivity to the cycloalkane-fused analogues and can be easily converted to the β-amino acid and its protected derivatives. The base-catalyzed isomerization of the cis-amino ester afforded the corresponding trans-amino ester in moderate yield.