ABSTRACT
Chiral syn-1,3-diols are fundamental structural motifs in many natural products and drugs. The traditional Narasaka-Prasad diastereoselective reduction from chiral ß-hydroxyketones is an important process for the synthesis of these functionalized syn-1,3-diols, but it is of limited applicability for large-scale synthesis because (1) highly diastereoselective control requires extra explosive and flammable Et2BOMe as a chelating agent under cryogenic conditions and (2) only a few functional syn-1,3-diol scaffolds are available. Those involving halogen-functionalized syn-1,3-diols are much less common. There are no reported diastereoselective reactions involving chemical fixation of CO2/bromocyclization of homoallylic alcohols to halogen-containing chiral syn-1,3-diols. Herein, we report an asymmetric synthesis of syn-1,3-diol derivatives via direct diastereoselective carboxylation/bromocyclization with both relative and absolute stereocontrol utilizing chiral homoallylic alcohols and CO2 in one pot with up to 91% yield, > 99% ee, and >19:1 dr. The power of this methodology has been demonstrated by the asymmetric synthesis of statins at the pilot plant scale.
ABSTRACT
A novel, stereoselective approach towards rosuvastatin calcium from the known (S)-homoallylic alcohol has been developed. The synthesis is highlighted by a regio- and stereocontrolled ICl-induced intramolecular cyclization of chiral homoallylic carbonate to deliver the C6-formyl statin side chain with a syn-1,3-diol moiety. An improved synthesis of the rosuvastatin pyrimidine core moiety is also included. Moreover, this methodology is useful in the asymmetric synthesis of structural variants of statins such as pitavastatin calcium and atorvastatin calcium and their related analogs.
Subject(s)
Chlorides/chemistry , Iodine/chemistry , Rosuvastatin Calcium/chemical synthesis , Cyclization , Molecular Structure , Rosuvastatin Calcium/chemistry , StereoisomerismABSTRACT
An efficient and concise asymmetric synthesis of pitavastatin calcium (1) starting from commercially available (S)-epichlorohydrin is described. A convergent C1 + C6 route allowed for the assembly of the pitavastatin C7 side chain via a Wittig reaction between phosphonium salt 2 and the enantiomerically pure C6-formyl side chain 3. The 1,3-syn-diol acetal motif in 3 was established with excellent stereo control by a diastereoselective bismuth-promoted two-component hemiacetal/oxa-Michael addition reaction of (S)-α,ß-unsaturated ketone 4 with acetaldehyde.
Subject(s)
Acetals/chemistry , Bismuth/chemistry , Calcium/chemistry , Ketones/chemistry , Quinolines/chemistry , Catalysis , Models, Chemical , Molecular Structure , Stereoisomerism , TemperatureABSTRACT
An efficient asymmetric synthesis of atorvastatin calcium has been achieved from commercially available diethyl 3-hydroxyglutarate through a novel approach that involves an organocatalytic enantioselective cyclic anhydride desymmetrization to establish C(3) stereogenicity and cyanide-free assembly of C7 amino type side chain via C5+C2 strategy as the key transformations.
Subject(s)
Calcium/chemistry , Cyanides/chemistry , Glutarates/chemistry , Heptanoic Acids/chemical synthesis , Hydroxymethylglutaryl-CoA Reductase Inhibitors/chemical synthesis , Pyrroles/chemical synthesis , Anhydrides , Atorvastatin , Heptanoic Acids/chemistry , Hydroxymethylglutaryl-CoA Reductase Inhibitors/chemistry , Pyrroles/chemistryABSTRACT
An efficient and reproducible process for the synthesis of methyl 2,3,4,5-tetradeoxy-7,8-O-isopropylidene-D-arabino-nanonate (2), a key intermediate in the total synthesis of (+)-biotin (1), starting from readily available D-mannose is described. The crucial part of this synthesis was the development of a practical route to a novel O-benzyl protected unsaturated ester methyl (benzyl 5,6,7,8-tetradeoxy-2,3-O-isopropylidene-alpha-D-lyxo-nona-5,7-dienofuranosid) uronate (7), allowing the one-step preparation of hydroxy ester methyl 5,6,7,8-tetradeoxy-2,3-O-isopropylidene-alpha-D-lyxo-nanofuranuronate (8) by the catalytic debenzylation and hydrogenation over palladium on carbon catalyst. This procedure requires no chromatographic purification, which makes it ideal for synthetic preparation on an industrial scale.
