79563-63-6

Upstream product

• 186581-53-3 diazomethane 
• 92572-82-2 2-(1-R-benzyloxy-1-cyclohexylmethyl)-1,3-oxathiane 
• 191982-83-9 (2R,4aR,7R,8aR)-2-((R)-1-Benzyloxy-ethyl)-4,4,7-trimethyl-hexahydro-1-oxa-3-thia-naphthalene 
• 89556-33-2 2-<(1'S)-1'-hydroxy-1'-phenylpropyl>hexahydro-4,4,7-trimethyl-4H-1,3-benzoxathiin 
• 89556-32-1 2-((1'S)-1'-hydroxy-1'-phenylethyl)hexahydro-4,4,7-trimethyl-4H-1,3-benzoxathiin 
• 92572-83-3 2-(1-R-benzyloxy-2,2-dimethylpropyl)-1,3-oxathiane 

Downstream Products

• 79563-59-0 (-)-(1R,2R,5R)-5-methyl-2-(1-mercapto-1-methylethyl)-cyclohexan-1-ol 

Relevant academic research and scientific papers

Preparation of (R)-(+)-Lithium Lactate

Optically pure (R)-(+)-lithium lactate (7) and its benzyl ether analogue (6a) were obtained from acetaldehyde using Eliel's 1,3-trans-oxathiane (1) as the chiral auxiliary for chromatographic separation.

Asymmetric Syntheses Based on 1,3-Oxathianes. 2. Synthesis of Chiral Tertiary α-Hydroxy Aldehydes, α-Hydroxy Acids, Glycols (RR'C(OH)CH2OH), and Carbinols (RR'C(OH)CH3) in High Enantiomeric Purity

A chiral 1,3-oxathiane (5) prepared from (+)-pulegone in three steps is converted to diastereomerically pure equatorial 2-acyl derivatives by lithiation, condensation with aldehydes, and Me2SO oxidation.Reaction of the resulting ketones with Grignard reagents at -78 deg C again proceeds highly stereoselectively (diastereomer excess generally above 90percent) according to Cram's rule (cyclic model).The resulting tertiary carbinols when cleaved with NCS/AgNO3 give chiral tertiary α-hydroxy aldehydes, RR'C(OH)CHO, plus a mixture of epimeric sultines which may be readily reconverted to the starting oxathiane.The hydroxy aldehydes have been oxidized to chiral tertiary α-hydroxy acids, RR'C(OH)CO2H, and reduced to primary-tertiary glycols, RR'C(OH)CH2OH, and further to tertiary carbinols, RR'C(OH)CH3, all with over 90percent ee.The opposite enantiomers of these compounds (again >90percent ee) may be obtained by starting with a diastereomeric 1,3-oxathiane (6), also available from (+)-pulegone.The configurations of the chiral products may be deduced from the manner of preparation and the assumption that Cram's rule is valid and agree with prior assignments in the literature.

ASYMMETRIC REACTIONS BASED ON 1,3-OXATHIANES-3. SECONDARY α-HYDROXYACIDS, RCHOHCO2H AND GLYCOLS RCHOHCH2OH

Reduction of the previously prepared chiral 2-acyl-1,3-oxathianes derived from (+)-pulegone with various metal hydride combinations proceeds stereoselectively, with diastereomer excess (d.e.) of as much as 97percent in the case of reduction of phenyl ketons with lithium tri-sec. butylborohydride.Lesser selectivity (maximum 82percent d.e.) is achived with primary or tertiary alkyl ketones: the predominant diastereomer is readily purified by chromatography.The major product in these cases is that predicted by Cram's chelate rule.The product ratio is reversed with diisobutylaluminium hydride and also in the reduction of secondary alkyl ketones with lithium sec. butylborohydride, where stereoselectivity is low.The 2-hydroxyalkyl-1,3-oxathines are cleaved to α-hydroxyaldehydes with N-chlorosuccinimide-silver nitrate and the aldehydes reduced to glycols, RCHOHCH2OH with sodium borohydride with little or no racemization.Esters, RCHOHCO2CH3, are obtained in high enantiomeric purity by O-benzylating the 2-hydroxyalkyl-1,3-oxathianes prior to cleavage, oxidizing with sodium chlorite following cleavage, esterifying and debenzylating.A method for measuring the enantiomeric purity of glycols RCHOHCH2OH by conversion to 2-phenyl-1,3-dioxolanes with benzaldehyde, followed by proton NMR analysis of the resulting 2-phenyl-4-alkyl-1,3-dioxolane diastereomer pair in the presence of a chiral europium shift reagent is described.