Compounds of the formula (I) wherein R is phenyl, or phenyl substituted by Cl, Br, C
1
-C
4
alkyl or CF
3
; R
1
is H or methyl or ethyl; R
2
is H or methyl or acyl; R
3
is H or methyl; R′
4
is —CH
3
or ═CH
2
; may be obtained in high enantiopurity by hydrogenation of a compound of the formula (II) wherein R and R
3
are as in formula (I); A is acyl; and R
4
is —CH
3
or ═CH
2
; in the presence of a chiral Rhodium or Ruthenium catalyst. Residues R
1
as methyl or ethyl and/or R
2
as H or methyl may subsequently be introduced without racemization by deacylation and optional alkylation.
式(I)的化合物中,其中R为苯基,或者被Cl、Br、C1-C4烷基或
CF3取代的苯基;R1为H、甲基或乙基;R2为H、甲基或酰基;R3为H或甲基;R'4为—
CH3或═
CH2。可以在手性
铑或
钌催化剂的存在下,通过对式(II)的化合物进行加氢反应来获得高对映纯度。其中,R和R3如式(I)中所示;A为酰基;R4为— 或═ 。可以通过去酰基和可选的烷基化来引入R1为甲基或乙基和/或R2为H或甲基残基,而不发生外消旋。