Synthesis of protected 4-oxopipecolic acid and 4-oxolysine using a palladium-catalysed coupling process

A Novel Approach for Mannich-Type Bases Having a Terminal Olefin: Zinc Triflate and Water-Promoted Cyclization/C−N Bond Cleavage Process

“…However, general preparation of pharmaceutically attractive β-aminoketones having a terminal olefin 1 by the reaction of aldimines with dienes bearing an enol ether moiety has not been reported yet because the [4 + 2] type cycloaddition generally proceeds to give cycloadducts 2 (Scheme ). , While the isolation of 1 has been reported, substituents of aldimines or dienes must be chosen carefully, , or a mixture of 1 and cycloadducts is obtained . In addition, other synthetic examples are complicated or not general, namely, (1) six steps from diethyl acetonylacetamidomalonate,5a (2) palladium(II)-assisted coupling process under severe temperature-controlled conditions, (3) hydrolysis of 6-vinyl-5,6-dihydro-4 H -1,3-oxazine which was formed by Diels−Alder reaction of 2-methoxy-1,3-butadiene with chloral acetylimine as a heterodiene . Here we report the first efficient Lewis acid system for general preparation of the Mannich-type bases having a terminal olefin 1 which cannot be prepared by widely known Mannich or Mannich-type reactions.…”

Synthesis of β-, γ-, δ-, ..., ω-Halogenated Ketones and Aldehydes

“…The resulting bromide 104 was not isolated, but treated with Na 2 CO 3 in H 2 O to affect cyclization toward 2-alkylated 3-pyrrolidinone 105. In the case of 4-piperidinone 108, HCl-mediated deprotection of the tert-butyloxycarbonyl group of enone 106 proceeded much slower than addition of the same acid across the unsaturation, which was evidenced by the isolation of β-chloro ketone 107 after 24 h. 55 A thorough investigation on the stereochemistry of the addition of HCl to endocyclic R,β-unsaturated ketones was reported by Blair and co-workers (Scheme 27). 56 For 1-benzoylcyclohexene 109, cis-1-benzoyl-2-chlorocyclohexane 112 was selectively obtained in excellent yield.…”

“…The resulting bromide 104 was not isolated, but treated with Na 2 CO 3 in H 2 O to affect cyclization toward 2-alkylated 3-pyrrolidinone 105 . In the case of 4-piperidinone 108 , HCl-mediated deprotection of the tert -butyloxycarbonyl group of enone 106 proceeded much slower than addition of the same acid across the unsaturation, which was evidenced by the isolation of β-chloro ketone 107 after 24 h …”

Enantioselective Synthesis of (2R,4S)- and (2S,4R)-4-Hydroxypipecolic Acid from d-Glucoheptono-1,4-lactone

“…Such a hydroxy acid was oxidized to the 4-oxo- l -pipecolic acid, which was then reduced to (−)- 1 . The same 4-ketoacid has been also synthesized in racemic or chiral forms, and it was employed as intermediate in another synthesis of (−)- 1 from l -aspartic acid . Enzymatic or quinine resolution of racemic 1 led to the optically pure compound .…”