本實驗室以先前開發的 3,5-雙取代 N-亞柳胺基酸錯合物催化 α-酮基苄基醯胺進行不對稱還原反應有初步的成果，我們接續先前的方針以 C3 位為特丁基取代， C5 位為溴基取代的 N-亞柳胺基酸衍生的氧釩錯合物 1a 搭配頻那醇硼烷，在氬氣與 −20 °C 下以無水甲苯為溶劑，對 α-酮基苄基醯胺之不對稱還原反應，可得產率 62% 與鏡像超越值 84% (R)-構型之 α-羥基苄基醯胺產物。另外，以 N-柳胺基酸衍生的氧釩錯合物 1a’ 配合兒茶酚硼烷作為還原劑進行反應，可以獲得較佳的產率 99% 與互補的鏡像超越值 64% (S)-構型之 α-羥基苄基醯胺產物。
在最佳化條件確立後，對一系列不同的 α-酮基苄基醯胺受質進行反應測試，其中以頻那醇硼烷搭配催化劑 1a 作為還原劑的例子中，受質之 α-酮基位置之官能基取代傾向平面及立體位阻較小的情況下會有較佳的鏡像超越值 (84-99%)；兒茶酚硼烷作為還原劑搭配催化劑 1a’ 的例子中，受質之 α-酮基位置之官能基取代傾向擁有較大芳香環系統的 2-萘基及立體位阻較小 2-噻吩基取代之受質擁有較佳的鏡像超越值 (72-76%)。
反應機構的推測中，受質之醯胺基的羰基會軸向配位到正五價氧釩中心，並與氧釩雙鍵存在於相反的位向，其中錯合物赤道位的甲氧基會與硼烷配位結合，其中體積較大的頻那醇硼烷使受質中的羰基與醯胺羰基形成特殊近垂直的構型環境，使得氫負離子傾向由看似立體位阻較大 C3-特丁基的 Si-face 位向加成，最終獲得 (R)-構型的產物。另一方面，兒茶酚硼烷與受質之間因芳香環之平面 π-π 作用力，使得受質中的羰基與醯胺羰基採取近共平面的 s-cis 構型環境；氫負離子傾向由遠離 C3-特丁基的 Re-face 位向加成，最終獲得 (S)-構型的產物。

We have developed a catalytic protocol for complementary enantioselective reduction of α-ketobenzylamide with pinacolborane and catecholborane catalyzed by chiral oxidovanadium (V) methoxides complexes derived from 3,5-disubstituted-N-salicylidene α-tert-leucinate.
The catalysts 1a and its reduce form 1a' (C3 = t-Bu, C5 = Br) with pinacholborane afforded upto 62% yield and 84% (R-form) enantioselectivity, at −20 °C in toluene under Argon. However, asymmetric reduction with catecholborane provides complementary enantioselectivity upto 64% (S-form) and 99% yield.
A series of α-ketobenzylamide substrates were examined, the substrates with small and planar α-keto functional groups can get better enantioselectivity. With pinacolborane, α-cinnamyl substituted system shows better enantioselectivity 93% (R-form) and 45% yield. While in the case of catecholborane, 2-thiophenyl case show better enantioselectivity 76% (S-form) and 89% yield.
The complementary enantioselectivity can be explained by a plausible mechanism, in which the step is the chelation of carbonyl group of amide with vanadyl(V) center axially anti to vanadyl oxygen . In the next step, the methoxide chelates with bulky pinacholborane lead to a s-trans conformation of the α-ketoamide and directs the hydride transfer from Si-face. This results in the formation of R-isomer. Conversely, the π-π interaction between the catecholborane and substrate coordinates in an s-cis conformation instigate the hydride transfer from Re-face. This results in the formation of S-isomer.

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