Isocyanide (3) attacks to re-face and si-face of 8E and 8Z and produces intermediate nitrilium ion 9R and 9S having one more
stereocenter. Finally, hydrolysis of 9 leads to the formation of aminoamides 4R and 4S.
The following discussion will assume a simple case, where there is only one
stereocenter and two mirror-image isomers.
Each
stereocenter can be either R or S configuration, and hence, the possible combinations are RRRR, RRSS, RRRS, RRSR, SSRR, SSSS, SSRS, SSSR, RSRR, RSSS, RSRS, RSSR, SRRR, SRSS, SRRS, and SRSR configurations.
The caffeine molecule lacks a
stereocenter and thus has no rotational isomers whatsoever.
Naringenin is the aglycone of the flavonoid glycoside naringin, a chiral natural product, usually with an S-configuration at the
stereocenter C2.
The reaction also includes the facet of
stereocenter control through the use of either L- or D- proline to give either the S or the R version of the product, respectively.
The compound 2 has two (adjacent)
stereocenters giving rise to two multiplets (2H) at 4.19.
Thus, the leading compound 32 with S-configuration of both
stereocenters has expressed antifungal activity against four highly aggressive clinical isolates of fungi belonging to C.
This disaccharide exists in two isomeric forms, [alpha]-lactose, and [beta]-lactose, which shows the phenomenon of mutarotation, that is, the interconversion of the
stereocenters [6].