uced inside the presence on the tert-butyl tert-butyl LiBH4, as well as the resultwas selectively selectively decreased within the presence of theester usingester employing LiBH4 , and also the resulting primary alcohol was O-benzoylated to cleavage from the tert-butyl tert-butyl ing key alcohol was O-benzoylated to 23. Acidic 23. Acidic cleavage of theester, actiester, in the carboxylic acid, and reapplication of the Evans auxiliary A supplied DPP-2 supplier oxazolvationactivation in the carboxylic acid, and reapplication in the Evans auxiliary A supplied oxazolidinone 24. Deprotonation of 24 and stereoselective developed azide 25. azide 25. idinone 24. Deprotonation of 24 and stereoselective azidationazidation producedJAK3 drug Catalytic Catalytic hydrogenation within the presence of Boc2 inside the formation on the N-Boc-protected hydrogenation within the presence of Boc2O resultedO resulted within the formation with the N-Bocprotected amino which was saponified saponified towards the corresponding amino acid 26. amino derivative, derivative, which was towards 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 reduced using triethylsilane in presence of trifluoroacetic dinone 27, which was decreased applying triethylsilane in presence of trifluoroacetic acid. Subacid. Subsequent cleavage from the Boc-protecting group necessary its reintroduction to 28. sequent cleavage of the Boc-protecting group necessary its reintroduction to 28.Mar. Drugs 2021, 19,vation from the carboxylic acid, and reapplication from the Evans auxiliary A offered oxazolidinone 24. Deprotonation of 24 and stereoselective azidation made azide 25. Catalytic hydrogenation within the presence of Boc2O resulted within the formation with 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 in to the corresponding oxazoli10 of 27 dinone 27, which was lowered using triethylsilane in presence of trifluoroacetic acid. Subsequent cleavage of the Boc-protecting group needed its reintroduction to 28.Scheme 6. Synthesis of protected hydroxyleucine 28 (creating block ). Scheme 6. Synthesis of protected hydroxyleucine 28 (building 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]. In accordance with Eastonaet diastereomeric mixture of your desired Wohl iegler bromination, providing a 1:1 1:1 diastereomeric mixture of thedesired bromo derivative bromination, giving al., therapy with the diastereomeric mixture bromo derivative [52]. In line with Easton et al., remedy of your diastereomeric mixture with AgNO3 in aqueous acetone made the desired (2S,3R)–hydroxyphenylalanine with AgNO3 in aqueous acetone producedstereochemical outcome might be explained by a enantio- and diastereoselectively [53]. The the desired (2S,3R)–hydroxyphenylalanine enantio- and diastereoselectively [53]. The stereochemicalthe subst
