Efficient Syntheses of (1R,2R)- and (1S,2S)-2-Amino-1-alkyl(or aryl)-1,3-propanediols by Regioselective Ring Opening of Aziridine-2-methanols

N-(1-Phenylethyl)aziridine-2-carboxylate esters in the synthesis of biologically relevant compounds

Since Garner’s aldehyde has several drawbacks, first of all is prone to racemization, alternative three-carbon chirons would be of great value in enantioselective syntheses of natural compounds and/or drugs. This review article summarizes applications of N-(1-phenylethyl)aziridine-2-carboxylates, -carbaldehydes and -methanols in syntheses of approved drugs and potential medications as well as of natural products mostly alkaloids but also sphingoids and ceramides and their 1- and 3-deoxy analogues and several hydroxy amino acids and their precursors. Designed strategies provided new procedures to several drugs and alternative approaches to natural products and proved efficiency of a 2-substituted N-(1-phenylethyl)aziridine framework as chiron bearing a chiral auxiliary.

Regioselectivity in the ring opening of non-activated aziridines

In this critical review, the ring opening of non-activated 2-substituted aziridines via intermediate aziridinium salts will be dealt with. Emphasis will be put on the relationship between the observed regioselectivity and inherent structural features such as the nature of the C2 aziridine substituent and the nature of the electrophile and the nucleophile. This overview should allow chemists to gain insight into the factors governing the regioselectivity in aziridinium ring openings (81 references).

Regio- and Stereoselective C-2 and C-3 Cleavage of 2-(1-Aminoalkyl)aziridines with Alcohols, Carboxylic Acids, and Sodium Iodide

Ring opening of nonactivated aziridines 1 using several nucleophiles, such as alcohols, carboxylic acids, and sodium iodide, is described. Depending on the nucleophile used, aziridines 1 are cleaved at C-3 or C-2 with total regio- and stereoselectivity, affording chiral 2-alkoxy-1,3-diamines 2 with alcohols, or O-acylated-1-hydroxy-2,3-diamines 6 with carboxylic acids in moderate or high yield. In the case of the aziridines derived from phenylalanine, treatment with NaI afford trans-4-phenylbut-3-en-1,2-diamines 9, generating the alkene with total diastereoselectivity. Mechanisms have been proposed to explain these reactions.

Novel stereoselective synthesis of functionalized oxazolidinones from chiral aziridines

Enantiomerically pure N-(R)-alpha-methylbenzyl-4(R)-(chloromethyl)oxazolidinones (4R)-5a-k were synthesized in one step and high yields from various aziridine-2-methanols (S)-2a-k by intramolecular cyclization with phosgene. The alpha-methylbenzyl substituent on the nitrogen was easily cleaved to give both enanatiomers of 4-(chloromethyl)oxazolidinones (R)-7a and (S)-7a. (R)-7a was used for the efficient syntheses of (L)-homophenylalaninol analogues (S)-12a-j. We also applied the same methodology to prepare oxazolidinones 9a-c containing a heteroatom-substituted alkyl group at C-4 in high yields.

A novel synthesis of 5-functionalized oxazolidin-2-ones from enantiomerically pure 2-substituted N-[(R)-(+)-alpha-methylbenzyl]aziridines

5-Funtionalized enantiomerically pure oxazolidin-2-ones were prepared in one pot from commercially available chiral aziridines bearing an electron-withdrawing group at C-2 with retention of the configuration in high yields by regioselective aziridine ring-opening followed by intramolecular cyclization.

A facile synthesis of enantiopure 2-aziridinesulfinimines and their highly diastereoselective reactions with phosphite anions

Two novel enantiopure 1-benzyl-2-aziridinesulfinimines bearing a chiral group on both sides of the carbon-nitrogen double bond were synthesized from the condensation of racemic 1-benzyl-2-aziridinecarboxaldehyde and enantiopure p-toluenesulfinamide. The addition reaction with phosphite anion followed by the ring-opening reaction with thiophenol provided chiral alpha,beta-diamino-phosphonic acid derivatives. The addition reactions showed the operation of a double-stereodifferentiation effect. The possible transition states of the reaction were proposed, and high diastereoselectivities of the addition reactions of phosphite anions to both aziridinesulfinimines were realized in the presence or absence of zinc bromide.

A facile and highly diastereoselective aziridination of chiral camphor n-enoylpyrazolidinones with n-aminophthalimide

Reaction of various chiral camphor N-enoylpyrazolidinones 2a-g with N-aminophthalimide in the presence of lead tetraacetate in CH(2)Cl(2) proceed smoothly afford the corresponding N-phthalimidoaziridines (3a-e, 4f-g) with excellent material yields (86-95%) at room temperature in 5 min. High levels of diastereoselectivities (up to >95:5 dr) were obtained. The solvent effect was investigated, and the auxiliary can be easily recovered in high yields under mild reaction conditions.