ABSTRACT
By using a methyl tetramate derivative (R)- or (S)-9 as a novel chiral building block, a direct, flexible, and highly enantioselective approach to methyl (R)- or (S)-5-alkyltetramates (2) is disclosed. Among the synthesized methyl 5-alkyltetramates 2, methyl 5-methyltetramate (2 a) is found in cytotoxic mirabimideâ E (4) and dysideapyrrolidone (5), and methyl 5-benzyltetramate (2 g) is a substructure in the potent antineoplastic dolastatinâ 15 (3). On the basis of this method, the first asymmetric synthesis of the antimitotic tetrapeptide belamideâ A (7) has been achieved in seven steps from (S)-9, with an overall yield of 23.8 %. Not only have the structure and absolute configuration of (+)-belamideâ A (7) been confirmed, but also the solvent used for recording the (13) Câ NMR spectrum, the (13) Câ NMR spectrum data correlation, and optical rotation data of natural belamideâ A (7) have been revised.
Subject(s)
Biological Products/chemistry , Biological Products/chemical synthesis , Marine Toxins/chemistry , Oligopeptides/chemistry , Oligopeptides/chemical synthesis , Pyrrolidinones/chemistry , Pyrrolidinones/chemical synthesis , Molecular Conformation , Molecular Structure , StereoisomerismABSTRACT
OBJECTIVE: To study the chemical constituents from Sarcopyramis nepalensis. METHODS: Compounds were isolated by D101 macroporous adsorption resin column and purified by repeatedly chromatographic techniques on Sephadex LH-20, silica gel and ODS columnl chromatograph. Their structures were elucidated by chemical and spectral methods. RESULTS: Six compounds were isolated from Sarcopyramis nepalensis, and identified as kaempferol (1), myricetic (2), dihydroquercetin (3), egllagic acid (4), isoferulic acid (5) and caffeic acid (6). CONCLUSION: All compounds are isolated from the genus for the first time.
Subject(s)
Cinnamates/isolation & purification , Ellagic Acid/isolation & purification , Kaempferols/isolation & purification , Melastomataceae/chemistry , Plants, Medicinal/chemistry , Caffeic Acids/chemistry , Caffeic Acids/isolation & purification , Cinnamates/chemistry , Ellagic Acid/chemistry , Flavonoids/chemistry , Flavonoids/isolation & purification , Kaempferols/chemistry , Molecular Structure , Quercetin/analogs & derivatives , Quercetin/chemistry , Quercetin/isolation & purification , Resins, SyntheticABSTRACT
Methyl tetramate derivative 6 has been developed as a new building block for the flexible and racemization-free synthesis of methyl 5-benzyl-3-methyltetramate via alkylation, and used in the first asymmetric synthesis of palau'imide (1). This allowed the establishment of the hitherto unknown stereochemistry at the C-20 of palau'imide as S.
Subject(s)
Biological Products/chemical synthesis , Imides/chemical synthesis , Oligopeptides/chemical synthesis , Pyrroles/chemical synthesis , Benzene/chemistry , Molecular Structure , StereoisomerismABSTRACT
(2S,3S,7S)-3,7-Dimethylpentadecan-2-yl acetate (2) and its propionate analogue (3) are the main sex pheromones of all Neodiprion species and Diprion similes, respectively. Starting from (S)-malic acid and employing a highly chemo-, regio-, and stereoselective tandem ester reduction-epoxide formation-reductive epoxide-opening reaction protocol, an efficient total synthesis of (2S,3S,7S)-2 and -3 is reported herein.
