Mild and selective ring-cleavage of cyclic carbamates to amino alcohols

Ishizuka, Tadao; Kunieda, Takehisa

doi:10.1016/s0040-4039(00)95574-6

Cited by 129 publications

(53 citation statements)

References 12 publications

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“…In the next step, cooled 0.1m t BuOK in dry THF was added dropwise at 08 to 0.1m d-(carbamoyloxy) ester 11 in THF, and the mixture was kept at 08 for 2.5 h. In accordance with the related studies made by Hirama and co-workers [15], the thermodynamically controlled, base-catalyzed aza-Michael cyclization of 11 to the 6-membered oxazinone system 22 succeeded with 80% chemical yield and remarkably To preserve the ethyl ester function of 22, the cleavage of the carbamate ring was first attempted under anhydrous biphasic conditions with carbonate (K 2 CO 3 , Na 2 CO 3 , Cs 2 CO 3 ) and hydroxide (KOH, NaOH) bases in various dry organic solvents (THF, DMF, MeCN, and CH 2 Cl 2 ), but this did not meet with success. Unlike the descriptions of Ishizuka and Kunieda [16], even the mild cleavage procedure via N-Boc activation of the carbamate ring did not produce the desired results. The only conditions capable of splitting the 1,3-oxazin-2-one into a free 1,3-amino alcohol required strong aqueous bases but were not compatible with the conservation of the ethyl ester function, so that the concomitant hydrolysis to the highly polar amino acid 23 could not be avoided.…”

contrasting

confidence: 65%

Enantioselective Entry to the Homalium Alkaloid Hoprominol: Synthesis of an (R,R,R)‐Hoprominol Derivative

Ensch¹,

Hesse²

2003

Helvetica Chimica Acta

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The diastereoselective synthesis of the N-and O-protected hoprominol derivative (R,R,R)-6 is described. The building up of the bicyclic O-silylated and di(N-tosylated) asymmetric scaffold 6 succeeded by convergent preparation of the two basic chiral azalactam units 7a and 7b and their subsequent iterative linking by a known method (Scheme 5). Both 4-alkyl-hexahydro-1,5-diazocin-2(1H)-ones 7a and 7b were prepared from the chiral b-amino acid portions 10a and 10b, respectively, by application of a set of reactions (e.g., N-alkylation of 10a,b and Sb(OEt) 3 -assisted cyclization of the resulting open-chain intermediates) already known. In comparison with the total syntheses of homaline (1) and homoprine (2), the newness of the described synthesis lies in the asymmetric approach to the difunctionalized fatty acid derivative 10b starting from (À)-(S)-malic acid (9) (Schemes 3 and 4). Key step in the preparation of 10b was the diastereoselective amination of the optically pure a,b-unsaturated d-hydroxy homoallylic ester 14 via conjugate intramolecular aza-Michael cyclization of the acylic d-(carbamoyloxy) intermediate 11.Introduction. ± Isolated from the leaves of the New Caledonian plant Homalium pronyense Guillaum. (Flacourtiaceae) [2], the four Homalium alkaloids homaline (1), hopromine (2), hoprominol (3), and hopromalinol (4) constitute a small family of optically active natural products characterized by a unique bis-eight-membered lactam structure incorporating a spermine (5) backbone (Fig.). The structures of the Homalium alkaloids were elucidated in the seventies by Pais and co-workers [3], and the correctness of the proposed formulae was confirmed by several total syntheses since then.A single-crystal X-ray analysis [4] as well as manifold asymmetric syntheses [5] [6] allowed the determination of the absolute (S,S)-configuration of the major alkaloid homaline (1). In a preceding paper [1], we presented a new, potent synthetic entry to the Homalium scaffold that enabled us to prepare (AE)-homaline (1) and (À)-hopromine (2) and, hence, to determine the absolute configuration of the natural hopromine (2) as being (R,R). Since, hitherto, all the syntheses of the remaining, unsymmetrically substituted parent molecules hoprominol (3) and hopromalinol (4) are nonstereospecific [7], the absolute configurations of the alkaloids 3 and 4 are still unknown. Hereafter, we now wish to report the application of our previously described synthetic strategy for building up the bicyclic Homalium core by the preparation of the N-and O-protected (R,R,R)-hoprominol precursor 6 (Fig.), with the higher aim of elucidating the yet-undefined configuration of the natural product (À)-homprominol (3).

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contrasting

confidence: 65%

Enantioselective Entry to the Homalium Alkaloid Hoprominol: Synthesis of an (R,R,R)‐Hoprominol Derivative

Ensch¹,

Hesse²

2003

Helvetica Chimica Acta

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“…yield, followed by oxazolidinone ring opening by treatment with cesium carbonate in methanol 41) to give optically active (S)-2-(Boc)amino-2-methyl-3-TBDMSoxypropanol (8c) in 77% yield. Dess-Martin oxidation of 8c proceeded smoothly to provide the corresponding aldehyde (11) in 73% yield.…”

Section: Chartmentioning

confidence: 99%

Dirhodium(II)-Catalyzed C-H Amination Reaction of (S)-3-(tert-Butyldimethylsilyloxy)-2-methylpropyl Carbamate: A Facile Preparation of Optically Active Monoprotected 2-Amino-2-methyl-1,3-propanediol

Yakura

Yoshimoto

Ishida

2007

CHEMICAL & PHARMACEUTICAL BULLETIN

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Dirhodium(II)-catalyzed C-H amination reaction of (S)-3-(tert-butyldimethylsilyloxy)-2-methylpropyl carbamate, which was easily prepared from methyl (S)-2-methyl-3-hydroxypropanoate, proceeded more smoothly than those of their 2-(methoxycarbonyl)propyl derivative to give the corresponding oxazolidinone in excellent yield. The resulting oxazolidinone was converted efficiently into both (R)-monoprotected and (S)-monoprotected 2-amino-2-methyl-1,3-propanediols.

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“…Protection of the carbamate nitrogen atom with a Boc group using Boc 2 O and DMAP in CH 3 CN afforded derivative 22 in 95% yield. Its exposure to mildly basic conditions (Cs 2 CO 3 , CH 3 OH)15 …”

mentioning

confidence: 99%

A stereoselective total synthesis of the HCl salts of mycestericins F, G and ent-F

Martinková

Gonda

Uhríková

et al. 2013

Tetrahedron: Asymmetry

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Mild and selective ring-cleavage of cyclic carbamates to amino alcohols

Cited by 129 publications

References 12 publications

Enantioselective Entry to the Homalium Alkaloid Hoprominol: Synthesis of an (R,R,R)‐Hoprominol Derivative

Enantioselective Entry to the Homalium Alkaloid Hoprominol: Synthesis of an (R,R,R)‐Hoprominol Derivative

Dirhodium(II)-Catalyzed C-H Amination Reaction of (S)-3-(tert-Butyldimethylsilyloxy)-2-methylpropyl Carbamate: A Facile Preparation of Optically Active Monoprotected 2-Amino-2-methyl-1,3-propanediol

A stereoselective total synthesis of the HCl salts of mycestericins F, G and ent-F

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