Practical synthesis of (3S,4S)-3-methoxy-4-methylaminopyrrolidine

Three synthetic methods for the preparation of (3S,4S)-3-methoxy-4-methylaminopyrrolidine, an important intermediate in the synthesis of the novel quinolone antitumor agent, AG-7352, have been developed. By one route, an efficient and large-scale preparation of the chiral pyrrolidine could be achieved through resolution of (±)-1-Boc-3-benzylamino-4-hydroxypyrrolidine, which is prepared from either 3-pyrroline or 1,4-dichloro-2-butene.     

Chemoenzymatic synthesis of (3R,4S)- and (3S,4R)-3-methoxy-4-methylaminopyrrolidine

An efficient and a convenient enantioselective synthesis of (3R,4S)-3-methoxy-4-methylaminopyrrolidine has been carried out by a lipase-mediated resolution protocol. This method describes the preparation of (±)-1-Cbz-cis-3-azido-4-hydroxypyrrolidine starting from commercially available diallylamine followed by ring-closing metathesis (RCM) via S_N2 displacement reactions. Pseudomonas cepacia lipase immobilized on diatomaceous earth (Amano PS-D) provides (3R,4S)-11 and (3S,4R)-12 in an excellent enantiomeric excess.     

Stereoselective synthesis of (3R,4S)-3-methoxy-4-methylaminopyrrolidine

An efficient stereoselective approach for the synthesis of (3R,4S)-3-methoxy-4-methylaminopyrrolidine, a part of the structure of quinoline antibacterial compound (1a) and the naphthyridine antitumour agent (1b) has been described.     

Chemoenzymatic synthesis of (3S,4S)- and (3R,4R)-3-methoxy-4-methylaminopyrrolidine

Facile chemoenzymatic enantioselective synthesis of (3S,4S)-3-methoxy-4-methylaminopyrrolidine, a key intermediate for a new quinolone antitumor compound AG-7352 has been described. This methodology illustrates the preparation of 3-azido-1-benzyloxycarbonyl-4-hydroxypyrrolidine starting from diallylamine via 1-benzyloxycarbonyl-3-pyrroline obtained by ring-closing metathesis (RCM) employing Grubbs’ catalyst. Enzymatic transesterification employing PS-C lipase gave (3S,4S)-3-azido-1-benzyloxycarbonyl-4-hydroxypyrrolidine in >99% ee, which upon methylation of the hydroxyl group followed by sequential reactions gave the desired intermediates, (3S,4S)-1-tert-butoxycarbonyl-3-tert-butoxycarbonylamino-4-methoxypyrrolidine.     

An efficient and stereospecific synthesis of (2S,4S)-2,4-diaminoglutaric acid

An efficient and stereospecific synthesis of (2S,4S)-2,4-diaminoglutaric acid 1 starting from trans-4-hydroxy-l-proline 2 is presented. The key step involves the combined application of ruthenium tetroxide (RuO₄) oxidation of 4-(tert-butoxycarbonylamino)proline derivatives 7 and 8 followed by regioselective ring opening of the resulting lactams 9 and 10 with 1 M LiOH.     

Total synthesis of (3R, 4S)-4-hydroxylasiodiplodin

Abstract

An alternative and concise total synthesis of (3?R, 4S)-4-Hydroxylasiodiplodin has been reported from inexpensive and commercially available 6-heptenal and Orsellinic acid starting materials. The key steps involved in the synthesis are Wittig reaction, Sharpless epoxidation, Yamaguchi esterification and ring-closing metathesis (RCM).     

Effective, high-yielding, and stereospecific total synthesis of D-erythro-(2R,3S)-sphingosine from D-ribo-(2S,3S,4R)-phytosphingosine

The synthesis of naturally occurring D-erythro-(2R,3S,4E)-sphingosine from commercially available D-ribo-(2S,3S,4R)-phytosphingosine is described. The key step in the reaction sequence comprises TMSI/DBN promoted regio- and stereoselective oxirane opening of intermediate 2-phenyl-4-(S)-[(1S,2S)-1,2-epoxyhexadecyl]-1,3-oxazoline followed by the in situ trans-elimination of 2-phenyl-4-(S)-[(1S,2R)-1,2-dideoxy-2-iodo-1-trimethylsilyloxyhexadecyl]-1,3-oxazoline.     

Novel,efficient and stereospecific synthesis of xylo-(2R,3S,4S)-phytosphingosine and threo-(2R,3R)-sphingosine

The stereo- and regioselective elaboration of a bromohydrin from an olefinic precursor and Pummerer ene reaction for carboncarbon bond formation are the key steps in a novel and flexible synthesis of xylo-phytosphingosine and threo-sphingosine.     

A Short and Efficient Synthesis of (3S,4S)-1-Benzyl-4-N-Benzylamino-3-Hydroxypiperidine

(3S,4S)-1-Benzyl-4-N-benzylamino-3-hydroxypiperidine 1 was efficiently synthesized from (S)-pyroglutaminol.     

Practical enantioselective synthesis of (3S, 4R)-3-hydroxypiperidine-4-carboxylic acid

A practical enantioselective synthesis of (3S, 4R)-3-hydroxypiperidine-4-carboxylic acid was accomplished via an unconventional Evans anti-aldol reaction followed by a one-pot azide reduction/reductive cyclization.     

Convenient synthesis of （2S,3R,4R,5S,6R）-2-（3-（4-ethylbenzyl）-4- chlorophenyl）-6-（hydroxymethyl）-tetrahydro- 2H-pyran-3,4,5-triol

A convenient approach for the preparation of （2S,3R,4R,5S,6R）-2-（3-（4-ethylbenzyl）-4-chlorophenyl）-6-（hydroxymethyl）- tetrahydro-2H-pyran-3,4,5-triol I is developed. The target compound via four steps is synthesized from 4-bromo-2-（bromomethyl）- 1-chlorobenzene and the isomers of undesired ortho-products were avoided during the preparation.     

A short, simple and general approach for the synthesis of (3S,4S)-3-methoxy-4-methylamino pyrrolidine and (3S,4R)-3-methoxy-4-methylamino pyrrolidine

A general and efficient stereoselective approach for the synthesis of (3S,4S) and (3S,4R)-3-methoxy-4-methylamino pyrrolidines, a part of the structure of AG-7352, a naphthyridine antitumor agent and quinoline antibacterial compounds has been described.     

Novel,short, stereospecific synthesis of lyxo-(2R,3R,4R)-phytosphingosine and erythro-(2R,3S)-sphingosine

Lyxo-phytosphingosine and erythro-sphingosine have been elaborated from a common intermediate. The key step in the reaction sequence involves stereo- and regiospecific functionalization of an olefin by intramolecular nucleophilic sulfinyl group participation.     

Efficient enantioselective synthesis of (2R,3R)- and (2S,3S)-3-hydroxyleucines and their diastereomers through dynamic kinetic resolution

(2R,3R)- and (2S,3S)-3-Hydroxyleucines, components of cyclodepsipeptides, papuamides and polyoxypeptins, were efficiently synthesized along with their diastereomers from the corresponding β-keto-α-amino acid ester through dynamic kinetic resolution using RuCl₂(binap)-catalyzed hydrogenation.     

Efficient synthesis of (S,S)-2,8-diazabicyclo[4.3.0]nonane

An efficient synthetic route for moxifloxacin chiral intermediate via five steps was established. First, dehydration, N-acylation, and cyclization were combined in one pot to meet the industrial requirement. Then relatively low hydrogen pressure was employed in the catalytic hydrogenation reaction with high yield. Isopropanol/water system was used in resolution, which guaranteed high yield and perfect optical purity. The racemic process conducted by manganese dioxide and Pd/C successfully converted the undesired enantiomer into the racemate and hence the total yield increased remarkably. Furthermore, mild hydrogen transfer catalytic hydrogenation method was utilized in debenzylation process instead of high-pressure hydrogenation. Total yield of 39.0% was achieved, which was much higher than that of 29.0% in literature.     

Stereoselective synthesis of (2R,3S,4S,5R)-trans-3,4-dihydroxy-5-(4-fluorophenoxymethyl)-2-(1-N-hydroxyureidyl-3-butyn-4-yl)tetrahydrofuran and (2R,3S,4S,5R)-trans-5-ethynyl-2-(4-fluorophenoxymethyl)-3,4-O-isopropylidene tetrahydrofuran from mannose diacetonide

Stereoselective synthesis of pharmaceutically interesting chiral tetrahydrofurans starting from mannose diacetonide is reported. A 1,4-diol system derived from mannose diacetonide, through a Mitsunobu reaction was stereospecifically cyclized to give chiral tetrahydrofurans. Both the C-1 and C-4 centers of d-mannose are successfully exploited to install the requisite side chains.     

The synthesis of (4S,5S)-(−)-isocytoxazone

(4S,5S)-(?)-Isocytoxazone, which is needed for a configurational study, was synthesized from the commercially available (1S,2S)-(+)-2-amino-1-(4-nitrophenyl)-1,3-propanediol in which the p-nitro substituent was replaced by a p-methoxyl group; the thus prepared p-methoxyphenyl amino diol was cyclized via an N-Boc derivative.