Aziridines ring synthesis

Water-solubilization 16, 501 Wenker aziridine ring synthesis 17, 537 Wessely-Moser rearrangement... 

Ethylenimines from 2-aminoalcohols via 2-aminosulfuric acid monoesters Wenker aziridine ring synthesis... 

S,3R)-Aziridine-2-carboxylic amide 258 (Scheme 3.95) has been used in the synthesis of the cyclic guanidino amino acid, L-epicapreomycidine (260) [145]. Treatment of 258 with saturated ammonia in methanol at 30 °C for 4 days in a pressure bottle resulted in the aziridine ring-opening product, which afforded 259 in 52 % yield after removal of the Cbz protecting group. 

Aziridines are important compounds due to their versatility as synthetic intermediates. In addition, aziridine rings are present in innumerable natural products and biologically active compounds. Nitrene addition to alkenes is one of the most well established methods for the synthesis of aziridines. Photolysis or thermolysis of azides are good ways to generate nitrenes. Nitrenes can also be prepared in situ from iodosobenzene diacetate and sulfonamides or the ethoxycarbonylnitrene from the A-sulfonyloxy precursor. 

The preparation of the required t/ireo-3-methylcysteine component in this synthesis, used the stereoselective ring opening of aziridinesJ62-63 It was shown to be possible to maintain stereospecificity of the reaction using the aziridine ring as an intermediate. 

Sugar azides are also important starting-materials for the synthesis of epimino sugars an azido group adjacent to a p-tolylsulfonyloxy group, as in 6 or 8, may be simultaneously reduced and cyclized with Raney nickel to form an aziridine ring, as in 7, especially if the two groups are in the frans-diaxial position.19 22... 

Scheme 13 Synthesis of /V -Boc-p-methylnaphthylalanine via Aziridine Ring Opening1271...

The synthesis of substituted cysteines can be accomplished via Michael addition reactions,]67124-126] by nucleophilic displacement,]127] from racemic thiazolines,]128] via aziridine ring opening,]129 and by asymmetric synthesis using a chiral auxiliary.]130] The details for some of these methods are described. 

The Gabriel-Cromwell reaction of amines with chiral c/., 3-unsaturated a-bromo carbonyl compounds was exploited for the synthesis of aziridine-2-carboxylic acid derivatives. 79 This procedure was optimized for a solid support synthesis in which the peptide resin was acylated with 2,3-dibromopropanoic acid active ester in the presence of 3 equivalents of NMM to produce directly on resin the a-bromoacrylamide for the addition of amines to produce the aziridine ring. 80 ... 

Alkylation of aziridines amine synthesis.3 N-Substituted aziridines (alkyl, benzyl, silyl, Boc) react with lithium dialkylcuprates in the presence of BF3 etherate (excess) with opening of the ring to give primary or secondary amines. 

In the absence of a base, the aziridine ring can be quaternized and opened by the nucleophile. A pyrrolizidine synthesis, in which such a reaction proceeds intramolecularly followed by a Michael addition (159), is shown as follows ... 

The thermolysis of triazoline adducts from other polycyclic bridgehead olefins is analogous to that of the norbornene-azide adducts (Scheme 164) and affords a route for the synthesis of various aziridine ring sys-... 

Aziridines can be readily prepared utilizing 1,2-amino leaving groups as precursors. Traditionally an amine lone pair or an amide anion facilitates an intramolecular nucleophilic displacement to generate the aziridine ring. Utilization of enantiomerically pure 1,2-amino leaving groups renders the possibility of enantiopure aziridines via asymmetric synthesis. 

Nitrogen-based nucleophiles continue to remain popular in ring-opening reactions of aziridines. a-Substituted-a-methoxycarbonyl-V-nosylaziridines were opened with a variety of functionalized amines to provide access to enantiopure a,a -disubstituted (3-lactam scaffolds for ditopic peptidomimetics <07OL101>. A related intramolecular regioselective 3,Y-aziridine ring opening with an a-amino functionality was reported in the synthesis of... 

---