uced within the presence from the tert-butyl tert-butyl LiBH4, and the resultwas selectively selectively reduced within the presence of theester usingester utilizing LiBH4 , and the resulting key alcohol was O-benzoylated to cleavage on the tert-butyl tert-butyl ing CA Ⅱ manufacturer primary alcohol was O-benzoylated to 23. Acidic 23. Acidic cleavage of theester, actiester, on the carboxylic acid, and reapplication of your Evans auxiliary A provided oxazolvationactivation with the carboxylic acid, and reapplication of the Evans auxiliary A offered oxazolidinone 24. Deprotonation of 24 and stereoselective developed azide 25. azide 25. idinone 24. Deprotonation of 24 and stereoselective azidationazidation producedCatalytic Catalytic hydrogenation within the presence of Boc2 in the formation of the N-Boc-protected hydrogenation in the presence of Boc2O resultedO resulted within the formation from the N-Bocprotected amino which was saponified saponified for the corresponding amino acid 26. amino derivative, derivative, which was to the corresponding amino acid 26. The preferred The preferred N-methyl group was by conversion of 26 in to the in to the corresponding N-methyl group was introduced introduced by conversion of 26corresponding oxazolioxazolidinone 27, which was lowered utilizing triethylsilane in presence of trifluoroacetic dinone 27, which was lowered working with triethylsilane in presence of trifluoroacetic acid. Subacid. Subsequent cleavage of your DP MedChemExpress Boc-protecting group required its reintroduction to 28. sequent cleavage of your Boc-protecting group necessary its reintroduction to 28.Mar. Drugs 2021, 19,vation of your carboxylic acid, and reapplication from the Evans auxiliary A supplied oxazolidinone 24. Deprotonation of 24 and stereoselective azidation developed azide 25. Catalytic hydrogenation inside the presence of Boc2O resulted within the formation from the N-Boc-protected amino derivative, which was saponified towards the corresponding amino acid 26. The desired N-methyl group was introduced by conversion of 26 into the corresponding oxazoli10 of 27 dinone 27, which was decreased utilizing triethylsilane in presence of trifluoroacetic acid. Subsequent cleavage of the Boc-protecting group needed its reintroduction to 28.Scheme six. Synthesis of protected hydroxyleucine 28 (building block ). Scheme 6. Synthesis of protected hydroxyleucine 28 (developing block 2 ).Mar. Drugs 2021, 19, x FOR PEER REVIEWThe unusual -methoxyphenylalanine was obtained from N-phthaloyl-protected 11 of 28 The unusual -methoxyphenylalanine four was obtained N-phthaloyl-protectedphenylalanine 29, which was converted into the corresponding tert-butylamide 30 corresponding tert-butylamide phenylalanine 29, which was converted (Scheme 7). Oxygen functionality was introduced into thethe -positionsubjecting 30 to30 (Scheme 7). Oxygen functionality was introduced into -position by by subjecting a to a Wohl iegler [52]. As outlined by Eastonaet diastereomeric mixture on the desired Wohl iegler bromination, supplying a 1:1 1:1 diastereomeric mixture of thedesired bromo derivative bromination, delivering al., treatment in the diastereomeric mixture bromo derivative [52]. In line with Easton et al., remedy from the diastereomeric mixture with AgNO3 in aqueous acetone created the desired (2S,3R)–hydroxyphenylalanine with AgNO3 in aqueous acetone producedstereochemical outcome is usually explained by a enantio- and diastereoselectively [53]. The the preferred (2S,3R)–hydroxyphenylalanine enantio- and diastereoselectively [53]. The stereochemicalthe subst
