Optically active N-protected .alpha.-amino aldehydes in organic synthesis

Synthesis of 2-amino alcohols and unnatural amino acids from serine

“…17,18 N-Protected α-aminoaldehydes may be prepared either by reduction of a carboxy derivative of an amino acid or by oxidation of 2-aminoalcohols, and it is known that they have a high tendency for racemization. 19 The NaOCl/TEMPO method was chosen because it appears superior to reductive methods in terms of preservation of the enantiomeric purity. Our strategy to synthesize unnatural α-amino acids was based on a Wittig-type olefination reaction of aldehyde 5.…”

A facile synthesis of N-Fmoc protected amino/peptidyl Weinreb amides employing acid chlorides as key intermediates

“…IR spectra were recorded on a Nicolet model Impact 400D FT-IR spectrometer (KBr pellets, 3 cm -1 resolution). 1 H NMR spectra were recorded on a Bruker AMX 300 MHz spectrometer using Me 4 Si as an internal standard and CDCl 3 solvent. Mass spectra were recorded on MALDI -TOF (KRATOS).…”

“…Much of their application in this field stems from the need for N-protected amino aldehydes which are important intermediates for many chemo selective transformations. 4 They are also useful in the synthesis of acetylenes 5 which are starting materials for the popular click reactions. 6 Reduction of Weinreb amides derived from Nprotected amino acids gives the corresponding aldehydes readily and this would give a better protocol for the synthesis of N-Fmoc-α-amino aldehydes which otherwise have to be synthesized either through the oxidation of corresponding alcohols or by careful reduction of esters.…”

α-Amino cyclic dithioketal mediated asymmetric synthesis of (S)-(-)-α-(N-p-toluenesulfonyl)aminopropiophenone (N-tosyl cathinone)

“…1,2 This protocol involves addition of 2-lithio-1,3-dithianes to enantiopure sulfinimines (N-sulfinyl imines) (S S )-1 to give N-sulfinyl α-amino cyclic dithioketals 2a (R' = alkyl, aryl) 3 and acetals 2b (R' = H) 4 in good yield and high diastereoselectivity (Scheme 1 2 ], affording the N-sulfinyl α-amino ketones (S S ,S)-4 without epimerization.…”

“…7 Several targeted asymmetric syntheses of the N-tosyl and the hydrochloride salt of this material have been described because α-amino ketones are not stable unless suitably N-protected. 1 These methods include ring opening of aziridines, 8 asymmetric aminohydroxylation of silyl enol ethers and alkenes, 9 catalytic asymmetric aziridination of enols, 10 and Friedel-Crafts acylation.…”