Optimisation of enantioselectivity for the chiral base-mediated rearrangement of bis-protected meso-4,5-dihydroxycyclohexene oxides: asymmetric synthesis of 4-deoxyconduritols and conduritol F
作者:Simon E de Sousa、Peter O'Brien、Christopher D Pilgram
DOI:10.1016/s0040-4020(02)00370-8
日期:2002.6
based on diastereoselective epoxidation of a cyclohexene followed by chiral lithium amide-mediated epoxide rearrangement has been used to synthesise an allylic alcoholbuildingblock of >95% ee. The key step is the enantioselective rearrangement of a bis-protected meso-4,5-dihydroxycyclohexene oxide. A range of protecting groups and chiral base structures were surveyed in order to find the optimum protocol
This invention relates to processes and intermediates for the stereoselective alkylation of carbonyl groups. The invention in particular allows the stereoselective preparation of the antidepressant drug escitalopram. It has been found that boric or boronic acid derivatives are useful bridging elements for the attachment of a chiral group to a compound containing a carbonyl group to be alkylated. The said borates and boronates are thus useful in a process for the asymmetric alkylation of a carbonyl group in a compound containing a carbonyl group and an anchor group capable of reacting with a boric or boronic acid derivative. The asymmetric alkylation can be carried out by admixing the compound containing a carbonyl group to be alkylated and the anchor group capable of reacting with a boric or boronic acid derivative with a boric or boronic acid derivative, adding a chiral alcohol, and adding an organometallic compound. After the alkylation reaction, the borate and boronate can be easily removed by hydrolysis.
[EN] CARBONYL ASYMMETRIC ALKYLATION<br/>[FR] ALKYLATION ASYMÉTRIQUE DE CARBONYLE
申请人:SANDOZ AG
公开号:WO2007082771A1
公开(公告)日:2007-07-26
[EN] This invention relates to processes and intermediates for the stereoselective alkylation of carbonyl groups. The invention in particular allows the stereoselective preparation of the antidepressant drug escitalopram. It has been found that boric or boronic acid derivatives are useful bridging elements for the attachment of a chiral group to a compound containing a carbonyl group to be alkylated. The said borates and boronates are thus useful in a process for the asymmetric alkylation of a carbonyl group in a compound containing a carbonyl group and an anchor group capable of reacting with a boric or boronic acid derivative. The asymmetric alkylation can be carried out by admixing the compound containing a carbonyl group to be alkylated and the anchor group capable of reacting with a boric or boronic acid derivative with a boric or boronic acid derivative, adding a chiral alcohol, and adding an organometallic compound. After the alkylation reaction, the borate and boronate can be easily removed by hydrolysis. [FR] La présente invention concerne des procédés et des intermédiaires destinés à l'alkylation stéréosélective de groupes carbonyle. L'invention permet en particulier la préparation stéréosélective du médicament antidépresseur escitaloprame. On a constaté que les dérivés d'acide borique ou boronique sont des éléments de pont utiles pour l'attachement d'un groupe chiral à un composé contenant un groupe carbonyle devant être alkylé. Lesdits borates et boronates sont ainsi utiles dans un procédé d'alkylation asymétrique d'un groupe carbonyle dans un composé contenant un groupe carbonyle et un groupe d'ancrage capable de réagir avec un dérivé d'acide borique ou boronique. L'alkylation asymétrique peut être effectuée par le mélange du composé contenant un groupe carbonyle devant être alkylé et le groupe d'ancrage capable de réagir avec un dérivé d'acide borique ou boronique avec un dérivé d'acide borique ou boronique, l'addition d'un alcool chiral et l'addition d'un composé organométallique. Après la réaction d'alkylation, le borate et le boronate peuvent être aisément éliminés par hydrolyse.