Thiazole and oxazole building blocks for combinatorial synthesis

Recent Advances in Application of Amino Acids: Key Building Blocks in Design and Syntheses of Heterocyclic Compounds

“…The active functional groups such as a C-terminal imino ester or a C-terminal aldehyde reacted with both amino groups and side chains of either serine or cysteine to form oxazolines or diasteriomeric mixtures of thiazolidines, respectively ( Figure 6) (99TL7951).…”

“…Apparently, MnO 2 oxidized the oxazoline to a more polar compound, instead of dehydrogenating it. Since the CuBr 2 /DBU/HMTA reagent requires that the oxazolines have a carbonyl group at 4 position, the more expensive nickel peroxide reagent was used to achieve dehydrogenation of oxazoline 119 (Scheme 27) (99TL7951).…”

Recent Advances in Biomimetic Synthesis Involving Cyclodextrins

“…Thio amide can a l s o b e r e p l a c e d b y t h i o u r e a o r a m m o n i u m dithiocarbamate, or dithiocarbamate, or dithiocarbamic acid or mono thio-carbamic acid or it's o-esters. Based on Hantzsch concept, some newer methods, such as cycloaddition of tosylmethyl isocyanide to thione derivatives (Bergstrom et al, 1994), oxidation of thiazoline and thiazolidine ring systems (Martin & Hu, 1999), the Ugi reaction (Kazmaier & Ackermann, 2005) and others (Mustafa et al, 2004), have been developed. Other methodologies developed include Pd-mediated coupling process (Sapountzis et al, 2005;Lipshutz et al, 2004;Nicolaou et al, 1999), nucleophilic reactions of Lithiothiazoles (Dondoni, 1998), solid supported synthesis to generate small organic molecule libraries (Kazzouli et al, 2002) and solution phase preparation of 2-aminothiazole combinatorial libraries (Bailey et al, 1996).…”

Directly Linked Polyazoles: Important Moieties in Natural Products

“…The thiazole-oxazole unit 80 (Scheme 29) was prepared using a novel strategy developed by Martin and Hu, 79 which consisted of the direct formation of a thiazolidine and an oxazoline during the efficient room-temperature condensation-cyclization step, wherein the peptide bond and ring-formation steps occur simultaneously. The thiazole ring was formed by reaction of the amino aldehyde 75 with L-cysteine methyl ester 76, followed by dehydrogenation of the thiazolidine 77 with MnO 2 , whilst the oxazole ring was prepared from the ethyl imidate 79 and the serine residue of thiazole 78 and subsequent oxidation with NiO 2 .…”