A New Highly Convergent Entry to Densely Functionalized Aziridines Based on the Ugi Reaction

Abstract

The products of an Ugi-4CR employing lactate-derived O-protected a-hydroxycarbonyl derivatives underwent, during the subsequent O-deprotection reaction, an unexpected acyl migration from nitrogen to oxygen. After ester saponification, treatment of the resulting a-aminoalcohol with mesyl chloride gave rise to a regioselective and stereospecific cyclization to give a series of highly functionalized aziridines in good overall yield.

Coupling Isocyanide-Based Multicomponent Reactions with Aliphatic or Acyl Nucleophilic Substitution Processes

“…For example, diketopiperazines have been generated starting from ahaloacids as carboxylic components. 38 The Ugi or Passerini adducts 54 and 57 derived from ahalo-, 28,39 a-sulfonyloxy-, 28 a-acyloxy-, 28,40 a-alkoxy- 40 or a-hydroxycarbonyl compounds 53 34 in principle can be manipulated to produce the respective b-lactams 55 and 58 through cyclization reactions involving the isocyanidederived NH group 28,39 (Scheme 13). In addition, oxazolines may be generated from the MCR adducts 54, provided that ammonia and not a primary amine is used in the Ugi reaction.…”

Tandem Ugi MCR/Mitsunobu Cyclization as a Short, Protecting‐Group‐Free Route to Benzoxazinones with Four Diversity Points

“…The use of glycolic acid as such under typical Ugi conditions (MeOH, room temp., 48 h) gave the adduct 2a in only 32 % yield. With (p-methoxybenzyloxy)acetic acid [32] the yield of the Ugi step was slightly better (43 %) but hydrogenolysis of the protecting group to give 2a (85 % yield) Table 1. Two-step synthesis of the benzoxazinones 1.…”

Enzymatically Asymmetrised Chiral Building Blocks for the Synthesis of Complex Natural Product Analogues: The Synthesis of Dynemicin Analogues from 2‐(Quinolin‐4‐yl)propane‐1,3‐diol

“…We therefore preferred to treat the crude product directly with K 2 CO 3 in methanol to bring about complete ester solvolysis and simultaneous removal of the Me 3 Si group. It is worth noting that these quite mild conditions for alkyne desilylation are not general for trimethylsilylalkynes, [68] being a particular feature of these systems. [21] The enantiomeric excess of alcohol (2R,2ЈR)-50a was determined by NMR analysis of its Mosher's ester, which indicated an ee of about 94 %, similar to that of the starting monoacetate 18.…”