Iterative Oxazole Assembly via α‐Chloroglycinates: Total Synthesis of (−)‐Muscoride A

Abstract

An efficient iterative synthesis of oxazoles involves the cyclization of 2‐alkynyl glycinates (see scheme) formed from the reaction of 1‐alkynyl aluminum reagents with α‐chloroglycinates. This approach was used in the total synthesis of the bisoxazole natural product, (−)‐muscoride A.

Microwave‐Assisted Cerium(III)‐Promoted Cyclization of Propargyl Amides to Polysubstituted Oxazole Derivatives

“…This efficient strategy could find application in the synthesis of substituted polyoxazoles. [33] In fact, a generic oxazole-4-carboxylic ester 5 could be converted into oxazole-4-carboxamide, which, after transformation into the corresponding functionalized propargyl amide, and subject to the cyclization described herein could give the corresponding bisoxazole. The generic polyoxazole would emerge after n such procedures.…”

Catalyst-Free Synthesis of Polysubstituted 5-Acylamino-1,3-Thiazoles via Hantzsch Cyclization of α-Chloroglycinates

“…Compounds 8 are readily available starting with a Ben-Ishai addition of a primary amide, 6 , to, e.g., ethyl glyoxylate, followed by reaction of the resultant 7 with SOCl 2 [39,40,41,42]. They are perfectly isolable and fairly stable on storage at −20 °C with exclusion of moisture (two weeks at least) [43,44,45,46,47], even though the halogen atom is quite labile. Also, they are normally obtained is a state of good to excellent purity; therefore, it is generally expedient to use them directly.…”

In Situ-Generated Glycinyl Chloroaminals for a One-Pot Synthesis of Non-proteinogenic α-Amino Esters

“…23 Several other solvents were tested (Table 1, entries 7–9), and α -chloroglycine 6a was also synthesized quantitatively in CH 3 CN in 24 h. After optimizations, two sets of conditions in CHCl 3 and CH 3 CN were established for the quantitative preparation of α -chloroglycine ester 6a in a single step, which represents an advancement from the previous literature (2 steps). 24 …”