Asymmetric PTC C-alkylation catalyzed by chiral derivatives of tartaric acid and aminophenols.: Synthesis of (R)- and (S)-α-methyl amino acids
Asymmetric PTC C-alkylation catalyzed by chiral derivatives of tartaric acid and aminophenols.: Synthesis of (R)- and (S)-α-methyl amino acids
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DOI：
10.1021/jo000719p
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发表时间：
2000-10-20
影响因子：
3.6
通讯作者：
Kagan, HB
中科院分区：
文献类型：
--
作者：
Belokon, YN;Kochetkov, KA;Kagan, HB
一种新型高效手性催化剂可在 PTC 条件下用于 CH 酸的不对称 C-烷基化。由酒石酸和氨基酚的手性衍生物（TADDOL's 2a-e和NOBLN's 3a-h）形成的钠醇盐可用作对映选择性烷基化中的手性催化剂，如由丙氨酸酯和苯甲醛衍生的席夫碱Pa-e与活性烷基卤化物的反应所例证。反应中形成的产物经酸催化水解得到(R)-α-甲基苯丙氨酸、(R)-α-萘基甲基丙氨酸和(R)α-烯丙丙氨酸，产率61-93%，ee 69-93%。该过程可以成功地扩展到 6 g 基板 1b。当使用(S,S)-TADDOL或(R)-NOBIN时，形成(S)-氨基酸。已经提出了一种合理化所观察到的反应特征的机制。
A new type of efficient chiral catalyst has been elaborated for asymmetric C-alkylation of CH acids under PTC conditions. Sodium alkoxides formed from chiral derivatives of tartaric acid and aminophenols (TADDOL's 2a-e and NOBLN's 3a-h) can be used as chiral catalysts in the enantioselective alkylation, as exemplified by the reaction of Schiff's bases Pa-e derived from alanine esters and benzaldehydes with active alkyl halides. Acid-catalyzed hydrolysis of the products formed in the reaction afforded (R)-alpha -methylphenylalanine, (R)-alpha -naphthylmethylalanine, and (R)alpha -allylalanine in 61-93% yields and with ee 69-93%. The procedure could be successfully scaled up to 6 g of substrate 1b. When (S,S)-TADDOL or (R)-NOBIN are used, the (S)-amino acids are formed. A mechanism rationalizing the observed features of the reaction has been suggested.