Syntheses of 3,3-Dimethyl-2-hydroxybutyric Acid and Tertiary Leucine and Their Optical Resolutions

Kutznerides 1−4, Depsipeptides from the Actinomycete Kutzneria sp. 744 Inhabiting Mycorrhizal Roots of Picea abies Seedlings

“…10,11 The other subunits of these depsipeptides have previously all been described, either as free molecules or as parts of peptides or other natural products. The synthesis and optical resolution of the enantiomers of OHdiMe-Bu has been described, 16 but to our knowledge, this is the first report of this R-hydroxy acid as part of a natural product. MecPGly has been isolated from Micromonospora miyakonensis 9 as a free amino acid, whereas OHGlu has been reported from different sources, e.g., in the peptidoglycan of Microbacterium lacticum.…”

“…The non-chlorinated analogue of diClPIC, i.e., PIC, has been shown to occur in peptides and proteins as a product of oxidation of tryptophan residues 12 as well as a product of oxidation of free tryptophan, but also as a constituent of peptides produced by bacteria and fungi. , The other subunits of these depsipeptides have previously all been described, either as free molecules or as parts of peptides or other natural products. The synthesis and optical resolution of the enantiomers of OHdiMeBu has been described, but to our knowledge, this is the first report of this α-hydroxy acid as part of a natural product. MecPGly has been isolated from Micromonospora miyakonensis 9 as a free amino acid, whereas OHGlu has been reported from different sources, e.g., in the peptidoglycan of Microbacterium lacticum …”

Stereoselective Synthesis of a Potent Thrombin Inhibitor by a Novel P2−P3 Lactone Ring Opening

“…The first approach to lactone ( S , R )- 16 centered on the synthesis of ( R )-3,3-dimethyl-2-hydroxybutyric acid [( R )- 14 ]. Although this is a relatively simple chiral hydroxy acid, and these types of molecules have been commonly used as synthetic building blocks, only sparse reports on the synthesis of either antipode of this molecule existed. − To develop an efficient approach to this compound, catalytic, asymmetric reductions of the corresponding α-ketoester 12 were investigated . Ethyl 3,3-dimethyl-2-oxobutanoate ( 12 ) was synthesized either by the addition of t -BuMgCl to diethyl oxalate ( 10 ) 23,24 or by the alkylation of 3,3-dimethyl-2-oxobutanoic acid ( 11 ) with EtBr/DBU. , Both methods rapidly afforded ketoester 12 27,28 in high yields (Scheme ).…”

Brucine

“…can be obtained with brucine, while the (−)-enantiomer crystallizes with cinchonidine 17. Additional examples of the same phenomenon can be found in the literature.1a …”