CHEMISTRY-A EUROPEAN JOURNAL 12(35) 8898-8925 2006年12月 査読有り
A carbonyl ylide cycloaddition approach to the squalene synthase inhibitors zaragozic acids A and C is described. The carbonyl ylide precursor 8 was synthesized starting from di-tert-butyl D-tartrate (47) via an eleven-step sequence involving the regioselective reduction of the mono-MPM (MPM -4-methoxybenzyl) ether 48 with LiBH4 and the diastereoselective addition of sodium tert-butyl diazoacetate to alpha-keto ester 10. The reaction of alpha-diazo ester 8 with 3-butyn-2-one (40) in the presence of a catalytic amount of [Rh-2(OAc)(4)] gave the desired cycloadduct 59 as a single diastereomer. The dihydroxylation of enone 59 followed by sequential transformations permitted the construction of the fully functionalized 2,8-dioxabicyclo [3.2.1]octane core 5. Alkene 79 derived from 5 serves as a common precursor to zaragozic acids A (1) and C (2), since the elongation of the C1 alkyl side chain can be attained by olefin cross-metathesis, especially under the influence of Blechert's catalyst (85).
A new, catalytic enantioselective route to 3-arylindan-1-ones, versatile intermediates for the synthesis of a number of bioactive and pharmaceutically interesting molecules, was developed by exploiting the chiral dirhodium(II) complex-catalyzed intramolecular C-H insertion reaction of alpha-diazo-beta-ketoesters as a key step. Dirhodium(II) tetrakis[N-phthaloyl-(S)-tert-leucinate], Rh-2(S-PTTL)(4), proved to be the catalyst of choice for this process, providing enantioselectivities of up to 72% ee.
A first example of chiral dirhodium(II) complex-catalyzed enantioselective Mukaiyama aldol reactions is described. The aldol addition reaction of methyl acetate-derived trimethylsilylketene acetal with specific aldehydes such as benzyloxyacetaldehyde and electron-poor aromatic aldehydes is effectively catalyzed by dirhodium(II) tetrakis[N-benzene-fused phthaloyl-(S)piperidinonate] (1a), providing silylated aldol adducts in up to 94% ee.
H Tsutsui, T Abe, S Nakamura, M Anada, S Hashimoto
CHEMICAL & PHARMACEUTICAL BULLETIN 53(10) 1366-1368 2005年10月 査読有り
An efficient and reliable procedure for the preparation of dirhodium(II) tetrakis[N-phthaloyl-(S)-tert-leucinate], Rh-2(S-PTTL)(4), a universally effective catalyst for a range of enantioselective carbene transformations, is described. The N-phthaloylation of (S)-tert-leucine by the method of Bose with essentially no racemization is a key to this process.
Excellent enantioselectivities (up to 99% ee) and turnover numbers (up to 48000) were attained in the hetero-Diels-Alder reaction of a diverse range of aldehydes and activated dienes catalyzed by [Rh2(S-bptpi) 4] (see scheme).
H Tsutsui, Y Yamaguchi, S Kitagaki, S Nakamura, M Anada, S Hashimoto
TETRAHEDRON-ASYMMETRY 14(7) 817-821 2003年4月 査読有り
Dirhodium(II) tetrakis[N-tetrafluorophthaloyl-(S)-tert-leucinate], Rh-2[(S)-TFPTTL](4), in which the phthalimido hydrogen atoms of the parent dirhodium(II) complex are substituted by fluorine atoms, dramatically enhances the reactivity and enantioselectivity (up to 97% ee) in intramolecular aromatic C-H insertion reactions of methyl 4-alkyl-2-diazo-4,4-diphenyl-3-oxopropionates. Catalysis with the use of 0.001 mol% of Rh-2[(S)-TFPTTL](4) has achieved the highest turnover number (up to 98,000 with the methyl substituent) ever recorded for chiral dirhodium(II) complex-catalyzed carbene transformations, without compromising the yield or enantioselectivity of the process. (C) 2003 Elsevier Science Ltd. All rights reserved.
Ketal isomers avoided. The unique 2,8-dioxabicyclo[3.2.1 ]octane core of zaragozic acid C (1) was constructed in a Rh-catalyzed 1,3-dipolar cycloaddition of an alkyne to an ester carbonyl ylide. Another feature of this improved synthesis is the construction of the alkyl side chain at C1 by olefin cross-metathesis.
Dirhodium(II) tetrakis[N-tetrachlorophthaloyl-(S)-tert-leucinate], characterized by substitution of chlorine atoms for four hydrogen atoms on the phthalimido group in the parent dirhodium(II) complex has been found to be well suited for enantioselective amidation of benzylic C-H bonds with [(4-nitrophenyl)sulfonylimino]phenyliodinane. The observed enantioselectivity of up to 84% ee is the highest reported to date for dirhodium(II) complex-catalyzed C-H amidations. (C) 2002 Elsevier Science Ltd. All rights reserved.
H Saito, H Oishi, S Kitagaki, S Nakamura, M Anada, S Hashimoto
ORGANIC LETTERS 4(22) 3887-3890 2002年10月 査読有り
[GRAPHICS]
The enantioselective intramolecular C-H insertion reaction of aryldiazoacetates has been explored with use of dirhodium(II) carboxylate catalysts, which incorporate N-phthaloyl- or N-benzene-fused-phthaloyl-(S)-amino acids as chiral bridging ligands. Dirhodium tetrakis[N-phthaloyl-(S)tert-leucinate], Rh-2(S-PTTL)(4), has proven to be the catalyst of choice for this process, providing exclusively cis-2-aryl-3-methoxycarbonyl-2,3-dihydobenzofurans in up to 94% ee.
S Kitagaki, Y Yanamoto, H Tsutsui, M Anada, M Nakajima, S Hashimoto
TETRAHEDRON LETTERS 42(36) 6361-6364 2001年9月 査読有り
Tandem intramolecular generation and rearrangement of allylic oxonium ylides from oc-diazo P-keto esters has been effected with the aid of dirhodium(II) tetrakis[N-phthaloyl-(S)-tert-leucinate] in toluene, providing benzofuran-3-ones via [2,3]-sigmatropic rearrangement in up to 76% cc. In systems with crotyl and prenyl substituents, products arising from the less common [1,2]-Stevens rearrangement as a side reaction have also been obtained in up to 66% ee. It is suggested that competitive [2,3]- and [1,2]-rearrangements proceed through a common, chiral rhodium(II)-bound oxonium ylide intermediate. (C) 2001 Elsevier Science Ltd. All rights reserved.
Enantioselective insertion reactions of methyl phenyldiazoacetate into the Si-H bond of silanes were effected by employing dirhodium(II) carboxylates incorporating N-phthaloyl-(S)-amino acids as chiral bridging ligands. The use of dirhodium(II) tetrakis [N-phthaloyl-(S) -phenylalaninate] as a catalyst produced methyl (2S)-(dimethylphenylsilyl)phenylacetate in 74% ee, whereas catalysis with dirhodium(II) tetrakis[N-phthaloyl-(S)-phenylglycinate] afforded its enantiomer in 72% ee. (C) 2000 Elsevier Science Ltd. All rights reserved.
S Kitagaki, M Yasugahira, M Anada, M Nakajima, S Hashimoto
TETRAHEDRON LETTERS 41(31) 5931-5935 2000年7月 査読有り
Enantioselective 1,3-dipolar cycloaddition of the ester-carbonyl ylides derived from methyl 2-(diazoacetyl)benzoate and 3-(diazoacetyl)-2-naphthoate with dipolarophiles has been effected with the aid of dirhodium(II) tetrakis[N-phthaloyl-(S)-tert-leucinate], affording cycloadducts in up to 93% ee. (C) 2000 Elsevier Science Ltd. All rights reserved.
A double asymmetric induction in intramolecular C-H insertion reaction of chiral, non-racemic α-diazo amides has been explored with the aid of dirhodium(II) tetrakis[N-phthaloyl-(R)- or (S)-phenylalaninate], Rh2(R- or S-PTPA)4, as a homochiral catalyst. The combination of α-methoxycarbonyl- α-diazoacetamide (13) with Rh2(S-PTPA)4 provides an 85:15 mixture of the desired 3-oxa-1-azabicyclo[4.2.0]octane derivative (14) and its diastereomer (15), which, upon reduction with LiBH4 and subsequent ready separation, leads to a key intermediate for the synthesis of 1β-methylcarbapenem antibiotics. Doyle-Taber's C-H insertion model coupled with the solid state structure of Rh2(S-PTPA)4 confirms the observed diastereomer preference.
A new route to (+)-α-allokainic acid commencing with L-serine has been established, wherein the key step involves a C3-C4 bond formation with a simultaneous creation of a C2, C3-trans and C3, C4-trans arrangement of substituents by Rh2(OAc)4-catalyzed C-H insertion reaction of α- diazoacetoacetamide tethered to (S)-4-(3-butenyl)-2,2-dimethyl-1,3- oxazolidine system. Taber's computational model confirms the observed diastereomer preference.
A new route to the phosphodiesterase type IV inhibitor (R)-(-)-rolipram (1) has been developed, wherein the key step relies on enantioselective intramolecular C-H insertion of N-alkyl-N-4-nitrophenyl-α-methoxycarbonyl- α-diazoacetamide 7 catalyzed by chiral dirhodium(II) complex. The dirhodium(II) carboxylate, Rh2(S-BPTTL)4, incorporating N-benzene-fused- phthaloyl-(S)tert-leucinate as a bridging ligand has proven to be the catalyst of choice for this process, providing the desired 2-pyrrolidinone 8 in 88% ee.
A new route to the enantiomerically pure azetidin-2-one 3, a key intermediate for the synthesis of trinems, has been developed, incorporating enantioselective intramolecular C-H insertion of alpha-methoxycarbonyl-alpha-diazoacetamide catalyzed by chiral Rh(II) complexes and diastereoselective arene hydrogenation as the key steps. The use of dirhodium(II) tetrakis[N-phthaloyl-(S)-tert-leucinate] as a catalyst produced the desired azetidinone in 84% ee, whereas catalysis with dirhodium(II) tetrakis[N-phthaloyl-(S)-alaninate] afforded its enantiomer in 84%ee. (C) 1998 Elsevier Science Ltd. All rights reserved.
Chemical Communications (15) 1517-1518 1998年8月 査読有り筆頭著者
A highly enantioselective construction of 3-oxa-1-azabicyclo[4.2.0]octanes (up to 96% ee) has been achieved by intramolecular C-H insertion of α-methoxycarbonyl-α-diazoacetamides catalysed by dirhodium(II) complexes incorporating N-phthaloyl-(S)-amino acids as chiral bridging ligands, which provides a new, catalytic asymmetric route to key intermediates for carbapenem antibiotics.
Site- and enantioselective intramolecular C-H insertion of α- methoxycarbonyl-α-diazoacetamides has been achieved by exploiting a p- nitrophenyl group as the N-substituent and dirhodium(II) tetrakis[N- phthaloyl-(S)-tert-leucinate] as catalyst, leading to the formation of 4 substituted 2-pyrrolidinone derivatives of up to 82% ee. The efficiency of the present protocol has been verified well by a short-step synthesis of (R)- (-)-baclofen.
The full potential of rhodium(II)-catalyzed intramolecular C-H insertion reactions of α-diazo carbonyl compounds as a powerful tool for the construction of both carbocycles and heterocycles has been developed by variation of the bridging ligands of the dirhodium(II) catalysts: (1) Dirhodium(II) tetrakis(triphenylacetate) featured by the steric bulk of the bridging ligands on the rhodium has been demonstrated to exhibit an exceptionally high order of selectivity for C-H insertion into methylene over methine on a cycloalkane ring as well as for aromatic substitution over aliphatic C-H insertion. (2) Dirhodium(II) complexes incorporating N-phthaloyl-(S)-amino acids as bridging ligands have proven to be the chiral catalysts of choice for allowing high levels of differentiation of enantiotopic methylene C-H bonds and enantiotopic benzene rings, affording optically active cyclopentanone, 2-azetidinone, and 2-indanone derivatives in up to 80%, 96%, and 98% ee, respectively.