1,2-Isopropylidene D-Glyceraldehyde as a Chiral Synthon for g-Butyrolactone

Abstract

~-1 , 2 -I e o p r o p y l i d e n e D-glyceraldehyde (3) i s shown to be a useful and inexpensive chiral starting material for s synthesis of Y-butyrolactones ( 8 ) ,

Diastereoselective Zwitterionic Aza-Claisen Rearrangement: The Synthesis of Bicyclic Tetrahydrofurans and a Total Synthesis of (+)-Dihydrocanadensolide

“…A major advantage is that the difficult synthesis of the corresponding N,N -dialkylacylamide dialkylacetals and the high reaction temperatures of the original Eschenmoser rearrangement 17 can be avoided. In contrast to the most common acyclic Claisen rearrangements, , high 1,2-asymmetric inductions were achieved with a range of acid chlorides, and the disappointing selectivity of the acetyl chloride reaction was overcome by the chloroacetyl chloride-rearrangement/dehalogenation sequence. The high simple diastereoselectivity (internal asymmetric induction) originates from the defined enolate geometry in a hypothetical zwitterionic intermediate.…”

“…In most cases the degree of 1,2-asymmetric induction (relative asymmetric induction) is low for the formation of a new C−C bond in α-position to a chiral C−O bond . Especially in acyclic substrates bearing glyceraldehyde or related fragments, high diastereoselectivities are more of an exception …”

Synthesis of 5-epi-Isofagomine via Asymmetric Chelate–Enolate Claisen Rearrangement

“…Optical rotations were measured on a Perkin-Elmer Polarimeter PE 241. (8): [17] A solution of 7 [16] (10 g, 63.5 mmol) in 100 ml of DMF was added to a stirred suspension of NaH (60% in oil) (3.82 g, 94.4 mmol) in 100 ml of DMF at Ϫ60°C. The mixture was warmed up, until a slight gas evolution was observed (at Ϫ30°C ).…”